| 单词 | meiosis |
| 例句 | We’re studying cell division right now, so for Halloween he dressed up as meiosis. The Science of Breakable Things 2018-03-06T00:00:00Z I don’t want to forget what I’ve learned, so I make mental diagrams of the respiratory system, the process of condensation, meiosis and mitosis. The Queen of Water 1996-01-01T00:00:00Z “Hey, can you tell me which phase of meiosis this cell is currently in?” The Science of Breakable Things 2018-03-06T00:00:00Z They orchestrate chaste sleepovers, during which they lie raptly awake “talking about The Sound and the Fury and meiosis and the Battle of the Bulge.” Are Tiny Books a Sign of the Twee-ification of Literary Culture? 2018-11-30T05:00:00Z "A significant contributor to infertility is defects in meiosis," said Billmyre. Why do some men not produce sperm? 2023-10-20T04:00:00Z The zygote undergoes mitosis and meiosis, resulting in more 1 n solitary amoebas. Fundamentals of Biology 2015-01-01T00:00:00Z On the other hand, meiosis is two nuclear divisions that result in four nuclei, usually partitioned into four new cells. Concepts of Biology 2013-04-25T00:00:00Z They named the trio of mutations MiMe, short for “mitosis instead of meiosis.” ‘Game changer.’ Scientists are genetically engineering crops to clone themselves 2023-05-17T04:00:00Z Physics provides the science and tools needed to generate the sequence of time-lapse images of meiosis similar to the sequence sketched in Figure 26.22. College Physics for AP Courses 2015-08-12T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z The diploid nucleus gives rise to haploid nuclei by meiosis. Fundamentals of Biology 2015-01-01T00:00:00Z The differences in the outcomes of meiosis and mitosis occur because of differences in the behavior of the chromosomes during each process. Concepts of Biology 2013-04-25T00:00:00Z During metaphase of meiosis II, the chromosomes line up in the center of each cell. Miller & Levine Biology 2018-01-01T00:00:00Z Only upon fertilization does the oocyte complete meiosis. Anatomy and Physiology 2013-06-19T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Aneuploidy results when the gametes have too many or too few chromosomes due to nondisjunction during meiosis. Fundamentals of Biology 2015-01-01T00:00:00Z Most of these differences in the processes occur in meiosis I, which is a very different nuclear division than mitosis. Concepts of Biology 2013-04-25T00:00:00Z Mitosis and meiosis also differ in the way chromosomes are divided between daughter cells and in their number of cell divisions. Miller & Levine Biology 2018-01-01T00:00:00Z The most common cause of trisomy 21 is chromosomal nondisjunction during meiosis. Anatomy and Physiology 2013-06-19T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Inside the sori, spores are produced by meiosis and released into the air. Fundamentals of Biology 2015-01-01T00:00:00Z All of these events occur only in meiosis I, never in mitosis. Concepts of Biology 2013-04-25T00:00:00Z A cell replicates, or copies, all of its chromosomes before entering either mitosis or meiosis. Miller & Levine Biology 2018-01-01T00:00:00Z Just prior to ovulation, a surge of luteinizing hormone triggers the resumption of meiosis in a primary oocyte. Anatomy and Physiology 2013-06-19T00:00:00Z The diploid zygote can then complete the sexual segment of the life cycle through meiosis. Biology for AP Courses 2022-06-09T00:00:00Z In the sporangia, mother cells undergo meiosis and produce the haploid spores. Fundamentals of Biology 2015-01-01T00:00:00Z Homologous chromosomes move to opposite poles during meiosis I so the number of sets of chromosomes in each nucleus- to-be is reduced from two to one. Concepts of Biology 2013-04-25T00:00:00Z In meiosis, homologous chromosomes are separated, and each daughter cell receives only a haploid set of chromosomes. Miller & Levine Biology 2018-01-01T00:00:00Z As in mitosis, DNA is replicated in a primary spermatocyte, before it undergoes a cell division called meiosis I. During meiosis I each of the 23 pairs of chromosomes separates. Anatomy and Physiology 2013-06-19T00:00:00Z To achieve this reduction in chromosome number, meiosis consists of one round of chromosome duplication and two rounds of nuclear division. Biology for AP Courses 2022-06-09T00:00:00Z After reaching maturity, the diploid sporophyte produces spores by meiosis, which in turn divide by mitosis to produce the haploid gametophyte. Fundamentals of Biology 2015-01-01T00:00:00Z Figure 7.6 Meiosis and mitosis are both preceded by one round of DNA replication; however, meiosis includes two nuclear divisions. Concepts of Biology 2013-04-25T00:00:00Z In meiosis, the two alleles for each gene are segregated and end up in different gamete cells. Miller & Levine Biology 2018-01-01T00:00:00Z Thus, meiosis results in separating the chromosome pairs. Anatomy and Physiology 2013-06-19T00:00:00Z Thus, meiosis I is the first round of meiotic division and consists of prophase I, prometaphase I, and so on. Biology for AP Courses 2022-06-09T00:00:00Z Through meiosis, the microsporangium forms microspores, and the megasporangium forms megaspores. Fundamentals of Biology 2015-01-01T00:00:00Z The process of meiosis produces genetically unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Concepts of Biology 2013-04-25T00:00:00Z The sorting and recombination of genes in meiosis increases genetic variation. Miller & Levine Biology 2018-01-01T00:00:00Z The LH surge induces many changes in the dominant follicle, including stimulating the resumption of meiosis of the primary oocyte to a secondary oocyte. Anatomy and Physiology 2013-06-19T00:00:00Z In each cell that undergoes meiosis, the arrangement of the tetrads is different. Biology for AP Courses 2022-06-09T00:00:00Z The Ring stage may multiply by mitosis or it may undergo meiosis, forming new 1n gametes of male or female sex types. Fundamentals of Biology 2015-01-01T00:00:00Z The process that results in haploid cells is called meiosis. Concepts of Biology 2013-04-25T00:00:00Z Mitosis and meiosis are two similar biological processes with important differences. Miller & Levine Biology 2018-01-01T00:00:00Z Fertilization occurs within the uterine tube, and the final stage of meiosis is completed. Anatomy and Physiology 2013-06-19T00:00:00Z In meiosis II, these two sister chromatids will separate, creating four haploid daughter cells. Biology for AP Courses 2022-06-09T00:00:00Z In the male cones, or staminate cones, the microsporocytes give rise to pollen grains by meiosis. Fundamentals of Biology 2015-01-01T00:00:00Z In meiosis, there are two rounds of nuclear division resulting in four nuclei and usually four haploid daughter cells, each with half the number of chromosomes as the parent cell. Concepts of Biology 2013-04-25T00:00:00Z This is not the case for meiosis, which reduces the chromosome number by half. Miller & Levine Biology 2018-01-01T00:00:00Z Identify some differences between meiosis in men and women. Anatomy and Physiology 2013-06-19T00:00:00Z Explain how an error in meiosis can cause these aberrations. Biology for AP Courses 2022-06-09T00:00:00Z Inside the anthers’ microsporangia, male gametophytes divide by meiosis to generate haploid microspores, which, in turn, undergo mitosis and give rise to pollen grains. Fundamentals of Biology 2015-01-01T00:00:00Z During meiosis, variation in the daughter nuclei is introduced because of crossover in prophase I and random alignment at metaphase I. The cells that are produced by meiosis are genetically unique. Concepts of Biology 2013-04-25T00:00:00Z A diploid cell that enters meiosis with eight chromosomes will pass through two meiotic divisions to produce four haploid daughter cells, each with four chromosomes. Miller & Levine Biology 2018-01-01T00:00:00Z The smaller cell, called the first polar body, may or may not complete meiosis and produce second polar bodies; in either case, it eventually disintegrates. Anatomy and Physiology 2013-06-19T00:00:00Z Errors during meiosis introduce variations in the DNA sequence, which depends specifically on the size of the variant only. Biology for AP Courses 2022-06-09T00:00:00Z The microspore undergoes meiosis, producing four cells, each of which becomes a grain of pollen with a hard coating. Fundamentals of Biology 2015-01-01T00:00:00Z The main differences between the processes occur in the first division of meiosis. Concepts of Biology 2013-04-25T00:00:00Z Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells. Miller & Levine Biology 2018-01-01T00:00:00Z There’s another called “The Biochemist,” where I’m having all these ideas, talking about the zygote, mitosis and meiosis. RZA on the current state of hip-hop: ‘The wisdom is missing’ 2022-04-05T04:00:00Z The two cells produced in meiosis I go through the events of meiosis II in synchrony. Biology for AP Courses 2022-06-09T00:00:00Z The life cycle of the brown algae, Laminaria, begins when sporangia undergo meiosis, producing 1n zoospores. Fundamentals of Biology 2015-01-01T00:00:00Z Recall that in meiosis these chromosomes are separated out into haploid gametes. Concepts of Biology 2013-04-25T00:00:00Z For example, when a complete set of chromosomes fails to separate during meiosis, the gametes that result may produce organisms with extra sets of chromosomes. Miller & Levine Biology 2018-01-01T00:00:00Z A few used them in ways that were arguably academic, walking up to the whiteboard and snapping a photo of the lesson on chromosomes and meiosis to copy it onto paper. ‘I Still Just Worry’: 3 Teachers on Covid’s Long Shadow Over American Schools 2022-03-19T04:00:00Z The mechanics of meiosis II is similar to mitosis, except that each dividing cell has only one set of homologous chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z When the zygospore germinates, it undergoes meiosis and produces haploid spores, which will, in turn, grow into a new organism. Fundamentals of Biology 2015-01-01T00:00:00Z Figure 8.11 The random segregation into daughter nuclei that happens during the first division in meiosis can lead to a variety of possible genetic arrangements. Concepts of Biology 2013-04-25T00:00:00Z If nondisjunction occurs during meiosis, gametes with an abnormal number of chromosomes may result, leading to a disorder of chromosome numbers. Miller & Levine Biology 2018-01-01T00:00:00Z The early part of meiosis consists of several steps. How sex chromosomes break up to get together 2020-05-26T04:00:00Z The nuclei resulting from meiosis are not genetically identical and they contain one chromosome set only. Biology for AP Courses 2022-06-09T00:00:00Z The filament supports the anther, where the microspores are produced by meiosis and develop into pollen grains. Fundamentals of Biology 2015-01-01T00:00:00Z The diploid primary spermatocyte goes through meiosis I to produce two haploid cells called secondary spermatocytes. Concepts of Biology 2013-04-25T00:00:00Z Drugs that prevent the separating of chromosomes during meiosis are useful in plant breeding. Miller & Levine Biology 2018-01-01T00:00:00Z Normally, oocytes progress more rapidly through early meiosis than do spermatocytes. How sex chromosomes break up to get together 2020-05-26T04:00:00Z The main differences between mitosis and meiosis occur in meiosis I, which is a very different nuclear division than mitosis. Biology for AP Courses 2022-06-09T00:00:00Z The mother cell undergoes meiosis to form a tetrad of cells, which separate to form the pollen grains. Fundamentals of Biology 2015-01-01T00:00:00Z Each secondary spermatocyte divides after meiosis II to produce two cells called spermatids. Concepts of Biology 2013-04-25T00:00:00Z Nondisjunction, the failure of homologous chromosomes to separate during meiosis, can lead to chromosome number disorders. Miller & Levine Biology 2018-01-01T00:00:00Z Acquaviva and colleagues’ model paints an elegant picture of how a genetic element, chromosome structure and the timing of meiosis interact to ensure proper recombination. How sex chromosomes break up to get together 2020-05-26T04:00:00Z Meiosis differs from mitosis in that the number of chromosomes is halved and genetic variation is reduced in meiosis, but not in mitosis. Biology for AP Courses 2022-06-09T00:00:00Z The microsporangium contains microspore mother cells, which divide by meiosis to produce haploid microspores. Fundamentals of Biology 2015-01-01T00:00:00Z Stamens are composed of a thin stalk called a filament and a sac-like structure, the anther, in which microspores are produced by meiosis and develop into pollen grains. Concepts of Biology 2013-04-25T00:00:00Z Most of the time, the process of meiosis works perfectly and each human gamete gets exactly 23 chromosomes. Miller & Levine Biology 2018-01-01T00:00:00Z They recognized that the distribution of chromosomes during mitosis and meiosis mirrored what was expected of Mendel’s hereditary ‘factors’, and showed that specific chromosomes were associated with sex. The forgotten scientists who paved the way to the double helix 2019-04-15T04:00:00Z Metaphase and telophase portions of meiosis and mitosis are the same. Biology for AP Courses 2022-06-09T00:00:00Z The megasporangium contains megaspore mother cells, which divide by meiosis to produce haploid megaspores. Fundamentals of Biology 2015-01-01T00:00:00Z A type of cell division called meiosis leads to the haploid cells that are part of the sexual reproductive cycle. Concepts of Biology 2013-04-25T00:00:00Z The most common error in meiosis occurs when homologous chromosomes fail to separate. Miller & Levine Biology 2018-01-01T00:00:00Z In 1882, he showed with great clarity their behaviour in the replication processes of mitosis and meiosis. The forgotten scientists who paved the way to the double helix 2019-04-15T04:00:00Z Spores are haploid cells formed only during asexual reproduction and so are not formed by meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Haploid spores are produced by meiosis within the sporangia, and spores can be disseminated through the air or water to potentially land in more favorable environments. Fundamentals of Biology 2015-01-01T00:00:00Z Variation is introduced during meiosis, as well as when the gametes combine in fertilization. Concepts of Biology 2013-04-25T00:00:00Z For example, if two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of that chromosome. Miller & Levine Biology 2018-01-01T00:00:00Z Diploid yeast can then divide through a process called meiosis to produce haploid spores that mature into haploid cells. Yeast chromosome numbers minimized using genome editing 2018-07-31T04:00:00Z If, during meiosis I, the cells are supplied with nitrogen, meiosis is halted. Biology for AP Courses 2022-06-09T00:00:00Z It will give rise, by meiosis, to the next generation of spores. Fundamentals of Biology 2015-01-01T00:00:00Z The process of meiosis reduces the resulting gamete’s chromosome number by half. Concepts of Biology 2013-04-25T00:00:00Z Meiosis involves two distinct cell divisions called meiosis I and meiosis II. Through meiosis, a single diploid cell produces four haploid cells. Miller & Levine Biology 2018-01-01T00:00:00Z During meiosis, genetic material is exchanged between paired chromosomes in a process called recombination. Yeast chromosome numbers minimized using genome editing 2018-07-31T04:00:00Z Construct an explanation as to how DNA is transmitted to the next generation via meiosis followed by fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Within the microsporangium, cells known as microsporocytes divide by meiosis to produce four haploid microspores. Fundamentals of Biology 2015-01-01T00:00:00Z Overall, meiosis II resembles the mitotic division of a haploid cell. Concepts of Biology 2013-04-25T00:00:00Z In prophase I of meiosis, each replicated chromosome pairs with its corresponding homologous chromosome. Miller & Levine Biology 2018-01-01T00:00:00Z This is unexpected, especially given that diploid hybrids that are sterile because of high sequence divergence or differently arranged genomes between their two sets of chromosomes can progress efficiently through meiosis, despite producing inviable spores7. Yeast chromosome numbers minimized using genome editing 2018-07-31T04:00:00Z Austrian monk Gregor Mendel set the framework for genetics long before chromosomes or genes had been identified, at a time when meiosis was not well understood. Biology for AP Courses 2022-06-09T00:00:00Z The megaspore mother cell divides by meiosis to produce four haploid megaspores. Fundamentals of Biology 2015-01-01T00:00:00Z Figure 7.8 Following meiosis, each gamete has one copy of each chromosome. Concepts of Biology 2013-04-25T00:00:00Z During metaphase I of meiosis, paired homologous chromosomes line up across the center of the cell. Miller & Levine Biology 2018-01-01T00:00:00Z These parts of the genome probably get repeated during meiosis, when a single cell divides to generate germ cells. Scientists are untangling our bodies’ genetic “double-edged swords” 2018-06-09T04:00:00Z In preparation for the first division of meiosis, homologous chromosomes replicate and synapse. Biology for AP Courses 2022-06-09T00:00:00Z First, in the process of megasporogenesis, a single cell in the diploid megasporangium—an area of tissue in the ovules—undergoes meiosis to produce four megaspores, only one of which survives. Fundamentals of Biology 2015-01-01T00:00:00Z Because they force chromosomes to assume contorted pairings during meiosis I, inversions and translocations are often associated with reduced fertility because of the likelihood of nondisjunction. Concepts of Biology 2013-04-25T00:00:00Z Inside the capsule, haploid spores are produced by meiosis and are scattered to begin the cycle again. Miller & Levine Biology 2018-01-01T00:00:00Z High-resolution mapping reveals a conserved, widespread, dynamic mRNA methylation program in yeast meiosis. The m1A landscape on cytosolic and mitochondrial mRNA at single-base resolution 2017-10-24T04:00:00Z Figure 12.18 The process of crossover, or recombination, occurs when two homologous chromosomes align during meiosis and exchange a segment of genetic material. Biology for AP Courses 2022-06-09T00:00:00Z The oogonia produce primary oocytes that are arrested in prophase I of meiosis from the time of birth until puberty. Fundamentals of Biology 2015-01-01T00:00:00Z Explain how the random alignment of homologous chromosomes during metaphase I contributes to variation in gametes produced by meiosis. Concepts of Biology 2013-04-25T00:00:00Z Near the base of each scale of the seed cones are two ovules, where haploid cells are produced through meiosis and grow and divide to produce female gametophytes. Miller & Levine Biology 2018-01-01T00:00:00Z His essay ended like that, and he sat down with the unaffected attitude of a student who had just read a paper about meiosis or the Louisiana Purchase. Chimamanda Ngozi Adichie, a Humanist On and Off the Page 2017-10-16T04:00:00Z When two genes are located in close proximity on the same chromosome, they are considered linked, and their alleles tend to be transmitted through meiosis together. Biology for AP Courses 2022-06-09T00:00:00Z “If you've got two genes linked together that can't cross over during meiosis, and one of them plays a role in sex determination, suddenly you can have a new sex chromosome.” The sparrow with four sexes 2016-11-22T05:00:00Z In what ways is meiosis II similar to and different from mitosis of a diploid cell? Concepts of Biology 2013-04-25T00:00:00Z Most reproductive biologists insist that the cells be caught in the act of undergoing meiosis, the cell division unique to sperm and eggs in which bits of DNA are swapped between chromosomes. Feature: A controversial company offers a new way to make a baby 2015-11-05T05:00:00Z The process of meiosis is also quite similar in mice and humans, and all mammals for that matter, vom Saal says. BPA Disrupts Sperm Development, Linked to Declining Male Fertility Because they correspond to new allele combinations, the genotypes Ab and aB are nonparental types that result from homologous recombination during meiosis. Biology for AP Courses 2022-06-09T00:00:00Z This includes the actual molecular events that are the basis of genetic variability, such as meiosis and DNA replication errors. 4 Tips to Prepare for the MCAT's New Natural Sciences Questions 2014-12-02T05:00:00Z Johann Gregor Mendel set the framework for genetics long before chromosomes or genes had been identified, at a time when meiosis was not well understood. Concepts of Biology 2013-04-25T00:00:00Z So far she is seeing markers of that cell division—proteins produced by meiosis genes. Feature: A controversial company offers a new way to make a baby 2015-11-05T05:00:00Z Figure 3: A genome structure incompatible with conventional meiosis. a, In twenty cases, allelic regions are found to occur on the same chromosome. Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga 2013-08-21T17:50:58.107Z If homologous chromosomes fail to separate during meiosis I, the result is two gametes that lack that particular chromosome and two gametes with two copies of the chromosome. Biology for AP Courses 2022-06-09T00:00:00Z What if, instead of dividing asexually through mitosis as an animal zygote does, the resulting zygote immediately underwent meiosis? Mosses Make Two Different Plants From the Same Genome, and a Single Gene Can Make the Difference 2013-05-12T19:45:00.233Z The genetic marker tends to be inherited with the gene of interest, and one measure of distance between them is the recombination frequency during meiosis. Concepts of Biology 2013-04-25T00:00:00Z Telfer acknowledges she still needs to record meiosis in action, and is planning those experiments. Feature: A controversial company offers a new way to make a baby 2015-11-05T05:00:00Z Allelic regions that are found on the same chromosome clearly cannot segregate during meiosis. Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga 2013-08-21T17:50:58.107Z Polyploid animals are sterile because meiosis cannot proceed normally and instead produces mostly aneuploid daughter cells that cannot yield viable zygotes. Biology for AP Courses 2022-06-09T00:00:00Z Mitalipov hypothesizes that “incomplete meiosis” — splitting of the cells — caused the problem, and he is now tweaking the method. DNA-Swap Technology Almost Ready for Fertility Clinic 2012-10-28T20:18:24.533Z Genetic maps provide an outline for the location of genes within a genome, and they estimate the distance between genes and genetic markers on the basis of the recombination frequency during meiosis. Concepts of Biology 2013-04-25T00:00:00Z But these cells didn’t enter meiosis, meaning they were, in Eppig’s words, “oocyte wannabes” and not the real thing. Feature: A controversial company offers a new way to make a baby 2015-11-05T05:00:00Z Such structure does not allow meiotic pairing; instead, we find abundant evidence of gene conversion, which may limit the accumulation of deleterious mutations in the absence of meiosis. Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga 2013-08-21T17:50:58.107Z Both are identified during meiosis by the adaptive pairing of rearranged chromosomes with their former homologs to maintain appropriate gene alignment. Biology for AP Courses 2022-06-09T00:00:00Z In you, meiosis generates eggs or sperm — either four sperm, or one egg and three degenerate polar bodies. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z One form of sympatric speciation can begin with a chromosomal error during meiosis or the formation of a hybrid individual with too many chromosomes. Concepts of Biology 2013-04-25T00:00:00Z The compound seems to target developing sperm both before and after meiosis, the special cell-division process that forms sperm and eggs, Matzuk says. 'The Pill' for Men Is Closer to Reality 2012-08-16T17:06:17Z Figure 3: A genome structure incompatible with conventional meiosis. a, In twenty cases, allelic regions are found to occur on the same chromosome. Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga 2013-08-21T17:50:58.107Z This inversion pairing is essential to maintaining gene alignment during meiosis and to allow for recombination. Biology for AP Courses 2022-06-09T00:00:00Z That is, inside the ascus, a diploid fungal nucleus undergoes meiosis — or sexual, reductive cell division — to produce ascospores. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The vast majority of eukaryotic organisms can or must employ some form of meiosis and fertilization to reproduce. Concepts of Biology 2013-04-25T00:00:00Z During meiosis, two cycles of cell division occur to produce gametes with only half of the number of chromosomes of the parent that produced them. Decoding the dance of the chromosomes 2012-06-22T03:15:09.577Z Takehiko Ogawa and colleagues at Yokohama City University discovered that the key to getting sperm through meiosis lay in a simple change to standard culture conditions. Sperm grown in a test tube 2011-03-23T23:15:00.267Z After meiosis, four haploid spores are produced, which can germinate. Biology for AP Courses 2022-06-09T00:00:00Z Incidentally, due to the filamentous fungal body plan, the spores that are the products of meiosis are ordered in most of these fungi. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z In addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes, and the genes are mixed into different combinations by the process of meiosis. Concepts of Biology 2013-04-25T00:00:00Z Mr. Orguly Bolp's large painting, entitled "Embrocation," is an interesting experiment in the handling of aplanatic surfaces, in which the toxic determinants are harmonized by a sort of plastic meiosis with syncopated rhythms. Punch, or the London Charivari, Vol. 150, April 5, 1916 This is a sort of hyperbole, and there is a corresponding meiosis, as: 'Mill admits that the Syllogism is useful'; when, in fact, that is Mill's contention. Logic Deductive and Inductive Cloning of cells through mitosis is molecularly much less complex than meiosis, consumes less energy, and is less risky. Biology for AP Courses 2022-06-09T00:00:00Z That is, unlike the indistinguishable groups of cells that are the product of plant and animal meiosis, the meiotic products of Neurospora and many ascomycetes are all kept in a neat row. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The replication of DNA occurs during the synthesis phase, or S phase, of the cell cycle, before the cell enters mitosis or meiosis. Concepts of Biology 2013-04-25T00:00:00Z The behaviour of the chromosomes in meiosis or reduction division both in the pollen mother-cells and in the megaspore mother-cells which give rise to the so-called embryo-sac are fully described by Gates. Hormones and Heredity "A meiosis in common use, equivalent to 'Yes, assuredly,'" murmured the Duke. Zuleika Dobson, or, an Oxford love story In one model, through assortment of genes, meiosis leads to an increase in the frequency of beneficial mutations. Biology for AP Courses 2022-06-09T00:00:00Z That means it’s possible to know which spores were the product of which cell division of meiosis. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z In the male cones, or staminate cones, the microsporocytes give rise to microspores by meiosis. Concepts of Biology 2013-04-25T00:00:00Z Under unfavourable conditions reduction or meiosis occurs, and two kinds of eggs larger and smaller are formed, both with N chromosomes. Hormones and Heredity As we will explore in more detail in a later chapter, errors in meiosis can cause genetic disorders, such as Down syndrome. Biology for AP Courses 2022-06-09T00:00:00Z Polyploidy results from an error in meiosis in which all of the chromosomes move into one cell instead of separating. Biology for AP Courses 2022-06-09T00:00:00Z In the diagram above, you can see the asci at various stages in meiosis. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The nuclear division that forms haploid cells, which is called meiosis, is related to mitosis. Concepts of Biology 2013-04-25T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z There must be at least one chiasma per chromosome for proper separation of homologous chromosomes during meiosis I, but there may be as many as 25. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z The crossover events are the first source of genetic variation in the nuclei produced by meiosis. Biology for AP Courses 2022-06-09T00:00:00Z To achieve the reduction in chromosome number, meiosis consists of one round of chromosome duplication and two rounds of nuclear division. Concepts of Biology 2013-04-25T00:00:00Z In meiosis, there are two rounds of nuclear division resulting in four nuclei and usually four daughter cells, each with half the number of chromosomes as the parent cell. Biology for AP Courses 2022-06-09T00:00:00Z The main differences between the processes occur in the first division of meiosis, in which homologous chromosomes are paired and exchange non-sister chromatid segments. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z The second division of meiosis is more similar to a mitotic division, except that the daughter cells do not contain identical genomes because of crossover. Biology for AP Courses 2022-06-09T00:00:00Z The crossover events are the first source of genetic variation produced by meiosis. Concepts of Biology 2013-04-25T00:00:00Z The process of meiosis produces unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Biology for AP Courses 2022-06-09T00:00:00Z However, the ways in which reproductive cells are produced and the timing between meiosis and fertilization vary greatly. Biology for AP Courses 2022-06-09T00:00:00Z Although self-fertilization forms seeds by meiosis, all of the resulting plants will be identical. Biology for AP Courses 2022-06-09T00:00:00Z The gene Ime1 is transcribed at the start of meiosis I in response to nitrogen starvation. Biology for AP Courses 2022-06-09T00:00:00Z Triploid animals are sterile because meiosis cannot proceed normally with an odd number of chromosome sets. Concepts of Biology 2013-04-25T00:00:00Z Explain the advantage provided to the population and the risk to individual cells of the timing of meiosis displayed in the graph above. Biology for AP Courses 2022-06-09T00:00:00Z Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains many fewer genes. Biology for AP Courses 2022-06-09T00:00:00Z These cells went through meiosis, an adaption of mitosis, which reduced the number of chromosomes in each reproductive cell by half, while increasing the number of cells through cell division. Biology for AP Courses 2022-06-09T00:00:00Z While studying meiosis, you observe that gametes receive one copy of each pair of homologous chromosomes and one copy of the sex chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z The physical basis of Mendel’s law of segregation is the first division of meiosis in which the homologous chromosomes with their different versions of each gene are segregated into daughter nuclei. Concepts of Biology 2013-04-25T00:00:00Z In 1913, Sturtevant devised a method to assess recombination frequency and infer the relative positions and distances of linked genes on a chromosome based on the average number of crossovers between them during meiosis. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z The section provides an opportunity to review the process of meiosis that we first explored in a previous chapter. Biology for AP Courses 2022-06-09T00:00:00Z Despite compelling correlations between the behavior of chromosomes during meiosis and Mendel’s abstract laws, the Chromosomal Theory of Inheritance was proposed long before there was any direct evidence that traits were carried on chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z This occurs because chromosomes, on which the genes reside, assort independently during meiosis and crossovers cause most genes on the same chromosomes to also behave independently. Concepts of Biology 2013-04-25T00:00:00Z Operating under these assumptions, Sturtevant postulated that alleles that were far apart on a chromosome were more likely to dissociate during meiosis simply because there was a larger region over which recombination could occur. Biology for AP Courses 2022-06-09T00:00:00Z One set of chromosomes has no pair so meiosis cannot proceed normally. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Sympatric speciation can occur through errors in meiosis that form gametes with extra chromosomes, called polyploidy. Concepts of Biology 2013-04-25T00:00:00Z Because they force chromosomes to assume unnatural topologies during meiosis, inversions and translocations are often associated with reduced fertility because of the likelihood of nondisjunction. Biology for AP Courses 2022-06-09T00:00:00Z Oocyte mitochondria are randomly segregated during meiosis, resulting in variation in the frequency of mtDNA mutations in offspring relative to the parent. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis. Biology for AP Courses 2022-06-09T00:00:00Z The second division of meiosis is much more similar to a mitotic division. Concepts of Biology 2013-04-25T00:00:00Z Genetic maps provide an outline for the location of genes within a genome, and they estimate the distance between genes and genetic markers on the basis of recombination frequencies during meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Explain the basis for the relationship you described in part a, in terms of what occurs to chromosomes during replication and meiosis. Biology for AP Courses 2022-06-09T00:00:00Z The cell produced at the end of meiosis is called a spermatid and when it reaches the lumen of the tubule and grows a flagellum, it is called a sperm cell. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains fewer genes. Concepts of Biology 2013-04-25T00:00:00Z The vast majority of eukaryotic organisms employs some form of meiosis and fertilization to reproduce. Biology for AP Courses 2022-06-09T00:00:00Z Although the processes of meiosis and mitosis share similarities, their end products are different. Biology for AP Courses 2022-06-09T00:00:00Z Four sperm result from each primary spermatocyte that goes through meiosis. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z When two genes are located on the same chromosome, they are considered linked, and their alleles tend to be transmitted through meiosis together. Concepts of Biology 2013-04-25T00:00:00Z As you have learned, the nuclear division that forms haploid cells— meiosis—is closely related to mitosis. Biology for AP Courses 2022-06-09T00:00:00Z In contrast, meiosis consists of two nuclear divisions resulting in four nuclei that are usually partitioned into four new cells. Biology for AP Courses 2022-06-09T00:00:00Z The cell starting meiosis is called a primary oocyte, as shown in Figure 34.15. Biology for AP Courses 2022-06-09T00:00:00Z Thinking outside the box and imagining what the early benefits from meiosis might have been is one approach to uncovering how it may have evolved. Biology for AP Courses 2022-06-09T00:00:00Z According to Mendel’s law of independent assortment, genes sort independently of each other into gametes during meiosis. Concepts of Biology 2013-04-25T00:00:00Z Meiosis and mitosis share obvious cellular processes and it makes sense that meiosis evolved from mitosis. Biology for AP Courses 2022-06-09T00:00:00Z Explain how the genetic makeup of these organisms differs from organisms that undergo meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Egg production begins before birth, is arrested during meiosis until puberty, and then individual cells continue through at each menstrual cycle. Biology for AP Courses 2022-06-09T00:00:00Z Crossing over or mixing of chromosomes does not occur in meiosis whereas it is prevalent in mitosis. Biology for AP Courses 2022-06-09T00:00:00Z The protein coils are further coiled, and during mitosis and meiosis, the chromosomes become even more greatly coiled to facilitate their movement. Concepts of Biology 2013-04-25T00:00:00Z The process of meiosis reduces the chromosome number by half. Biology for AP Courses 2022-06-09T00:00:00Z The zygote immediately undergoes meiosis to form four haploid cells called spores. Biology for AP Courses 2022-06-09T00:00:00Z Both are the form of gametogenesis that takes place through meiosis. Biology for AP Courses 2022-06-09T00:00:00Z The diploid plant is called a sporophyte because it produces haploid spores by meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Within 24 hours of fertilization, the egg nucleus has finished meiosis and the egg and sperm nuclei fuse. Concepts of Biology 2013-04-25T00:00:00Z However, at some point in each type of life cycle, meiosis produces haploid cells that will fuse with the haploid cell of another organism. Biology for AP Courses 2022-06-09T00:00:00Z Meiosis differs from mitosis in that the number of chromosomes is halved and genetic variation is introduced in meiosis, but not in mitosis. Biology for AP Courses 2022-06-09T00:00:00Z Both are the form of gametogenesis that takes place through meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Prophase and telophase portions of meiosis and mitosis are the same. Biology for AP Courses 2022-06-09T00:00:00Z Explain how the orientation of homologous chromosomes during metaphase I of meiosis contributes to greater variation in gametes. Biology for AP Courses 2022-06-09T00:00:00Z How does the segregation of traits result in different combinations of gametes at the end of meiosis? Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z A haploid oogonium forms a diploid oocyte by the process of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Down Syndrome is a genetic, developmental condition caused by nondisjunction of chromosome 21 during meiosis. Biology for AP Courses 2022-06-09T00:00:00Z The main difference is in the type of cell produced: mitosis produces identical cells, allowing growth or repair of tissues; meiosis generates reproductive cells, or gametes. Biology for AP Courses 2022-06-09T00:00:00Z During meiosis II—which is more similar to a mitotic division—the chromatids separate and segregate into four haploid sex cells. Biology for AP Courses 2022-06-09T00:00:00Z Errors during anaphase I of meiosis only cause such aberrations resulting in unequal numbers of chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z A diploid oogonium forms a haploid oocyte by the process of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z For this reason, meiosis I is referred to as a reduction division. Biology for AP Courses 2022-06-09T00:00:00Z Figure 11.7 Meiosis and mitosis are both preceded by one round of DNA replication; however, meiosis includes two nuclear divisions. Biology for AP Courses 2022-06-09T00:00:00Z The four daughter cells resulting from meiosis are haploid and genetically distinct. Biology for AP Courses 2022-06-09T00:00:00Z The difficulty lies in the clear differences between meiosis I and mitosis. Biology for AP Courses 2022-06-09T00:00:00Z A haploid oogonium forms a haploid haploid oocyte by the process of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z There are other approaches to understanding the evolution of meiosis in progress. Biology for AP Courses 2022-06-09T00:00:00Z Different forms of meiosis exist in single-celled protists. Biology for AP Courses 2022-06-09T00:00:00Z Some appear to be simpler or more “primitive” forms of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Comparing the meiotic divisions of different protists may shed light on the evolution of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Although research is still ongoing, recent scholarship into meiosis in protists suggests that some aspects of meiosis may have evolved later than others. Biology for AP Courses 2022-06-09T00:00:00Z This kind of genetic comparison can tell us what aspects of meiosis are the oldest and what cellular processes they may have borrowed from in earlier cells. Biology for AP Courses 2022-06-09T00:00:00Z Which of the following events occurs in both mitosis and meiosis I? Biology for AP Courses 2022-06-09T00:00:00Z Organisms reproducing through mitosis produce genetically different daughter cells whereas those producing through meiosis have genetically identical daughter cells. Biology for AP Courses 2022-06-09T00:00:00Z In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Mitosis is a process of asexual reproduction in which the number of chromosomes are reduced by half producing two haploid cells whereas in meiosis two diploid cells are produced by cell division. Biology for AP Courses 2022-06-09T00:00:00Z In meiosis, two parents produces gametes and the offspring have only half the number of chromosomes of each parent and hence genetic variation is introduced. Biology for AP Courses 2022-06-09T00:00:00Z Identifying the haploid and diploid stages within the life cycles of different organisms is vital in understanding how organisms reproduce and in determining when mitosis and meiosis occur. Biology for AP Courses 2022-06-09T00:00:00Z Germ cells are capable of mitosis to perpetuate the cell line and meiosis to produce gametes. Biology for AP Courses 2022-06-09T00:00:00Z The first division, meiosis I, separates homologous chromosomes, and the second division, meiosis II, separates chromatids. Biology for AP Courses 2022-06-09T00:00:00Z Specialized cells of the sporophyte will undergo meiosis and produce haploid spores. Biology for AP Courses 2022-06-09T00:00:00Z Punnett squares are useful tools that apply the rules of probability and meiosis to predict the possible outcomes of genetic crosses. Biology for AP Courses 2022-06-09T00:00:00Z The physical basis of Mendel’s law of segregation is the first division of meiosis, in which the homologous chromosomes with their different versions of each gene are segregated into daughter nuclei. Biology for AP Courses 2022-06-09T00:00:00Z The physical basis for the law of independent assortment also lies in meiosis I, in which the different homologous pairs line up in random orientations. Biology for AP Courses 2022-06-09T00:00:00Z Although mitosis and meiosis are similar in many ways, they have different outcomes. Biology for AP Courses 2022-06-09T00:00:00Z It is now known that homologous chromosomes regularly exchange segments in meiosis by reciprocally breaking and rejoining their DNA at precise locations. Biology for AP Courses 2022-06-09T00:00:00Z Chromosomal crossover occurs during meiosis when chromosome pairs are linked and exchange DNA. Biology for AP Courses 2022-06-09T00:00:00Z |
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