| 单词 | haploid |
| 例句 | In this case, the ants have haploid cells from two divergent lineages: R and W. Humans, for example, have X and Y haploid cells. These invasive ants have bizarre genomes that defy biology 2023-07-24T04:00:00Z A variety of algal life cycles exists, but the most complex is alternation of generations, in which both haploid and diploid stages involve multicellularity. Fundamentals of Biology 2015-01-01T00:00:00Z Human cells that contain one set of 23 chromosomes are called gametes, or sex cells; these eggs and sperm are designated n, or haploid. Concepts of Biology 2013-04-25T00:00:00Z He also noted that gourds have a lot of diversity in their gene pool: cucumbers only have 7 haploid chromosomes, while watermelons have 11. Gourds, the dogs of the plant world, can be one pound or 1,000. Geneticists think they know why 2022-11-19T05:00:00Z The yeast life cycle is usually dominated by haploid cells, each with a single set of unpaired chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z 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 Certain other organisms perform alternation of generations in which both the haploid and diploid forms look the same. Fundamentals of Biology 2015-01-01T00:00:00Z Cytokinesis separates the two cells into four genetically unique haploid cells. Concepts of Biology 2013-04-25T00:00:00Z Because each of these reproductive cells is a haploid cell containing half of the genetic material needed to form a human being, their combination forms a diploid cell. Anatomy and Physiology 2013-06-19T00:00:00Z However, the starting nucleus is always diploid and the nuclei that result at the end of a meiotic cell division are haploid. Biology for AP Courses 2022-06-09T00:00:00Z 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 Cells atop the stalk form an asexual fruiting body that contains haploid spores. Fundamentals of Biology 2015-01-01T00:00:00Z At this point, the nuclei in the newly produced cells are both haploid and have only one copy of the single set of chromosomes. Concepts of Biology 2013-04-25T00:00:00Z At this moment, the oocyte has become an ovum, the female haploid gamete. 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 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 The diploid nucleus gives rise to haploid nuclei by meiosis. 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 One of the sperm will then break through to the oocyte’s plasma membrane and release its haploid nucleus into the oocyte. Anatomy and Physiology 2013-06-19T00:00:00Z They have the same number of sets of chromosomes, one set in the case of haploid cells and two sets in the case of diploid cells. Biology for AP Courses 2022-06-09T00:00:00Z 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 Four major adaptations are found in all terrestrial plants: the alternation of generations, a sporangium in which the spores are formed, a gametangium that produces haploid cells, and apical meristem tissue in roots and shoots. 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 Fertilization is complete upon unification of the haploid nuclei of the two gametes, producing a diploid zygote. Anatomy and Physiology 2013-06-19T00:00:00Z Haploid dominant life cycles have a multicellular haploid stage, as in fungi. Biology for AP Courses 2022-06-09T00:00:00Z The human haploid genome is larger than the genome of many other organisms. Miller & Levine Biology 2018-01-01T00:00:00Z The plant life cycle has haploid and diploid stages. 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 Although haploid, early spermatids look very similar to cells in the earlier stages of spermatogenesis, with a round shape, central nucleus, and large amount of cytoplasm. Anatomy and Physiology 2013-06-19T00:00:00Z In alternation of generations, both haploid dominant and diploid dominant stages alternate, as in plants. Biology for AP Courses 2022-06-09T00:00:00Z Many protists have sexual life cycles in which they switch between a diploid and a haploid phase, a process known as alternation of generations. Miller & Levine Biology 2018-01-01T00:00:00Z Most plants exhibit alternation of generations, which is described as haplodiplodontic: the haploid multicellular form, known as a gametophyte, is followed in the development sequence by a multicellular diploid organism: the sporophyte. Fundamentals of Biology 2015-01-01T00:00:00Z Meiosis and its associated cell divisions produces haploid cells with half of each pair of chromosomes normally found in diploid cells. Concepts of Biology 2013-04-25T00:00:00Z The head of the sperm contains the extremely compact haploid nucleus with very little cytoplasm. Anatomy and Physiology 2013-06-19T00:00:00Z In a diploid dominant cycle, a multicellular haploid stage is present, as in humans. Biology for AP Courses 2022-06-09T00:00:00Z This shift between the haploid phase and the diploid phase is known as the alternation of generations. Miller & Levine Biology 2018-01-01T00:00:00Z In the sporangia, mother cells undergo meiosis and produce the haploid spores. 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 How does the diploid secondary oocyte become an ovum—the haploid female gamete? Anatomy and Physiology 2013-06-19T00:00:00Z In a haploid dominant life cycle, a multicellular diploid stage is present, as in fungi. Biology for AP Courses 2022-06-09T00:00:00Z Many green algae have life cycles that switch back and forth between haploid and diploid phases. Miller & Levine Biology 2018-01-01T00:00:00Z The haploid gametophyte produces the male and female gametes by mitosis in distinct multicellular structures. Fundamentals of Biology 2015-01-01T00:00:00Z Haplontic refers to a life cycle in which there is a dominant haploid stage. Concepts of Biology 2013-04-25T00:00:00Z Thus, the ovum can be thought of as a brief, transitional, haploid stage between the diploid oocyte and diploid zygote. Anatomy and Physiology 2013-06-19T00:00:00Z In alternation of generations, both haploid dominant and diploid dominant stages alternate, as in plants. Biology for AP Courses 2022-06-09T00:00:00Z 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 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 When the haploid spore germinates, it generates a multicellular gametophyte by mitosis. Concepts of Biology 2013-04-25T00:00:00Z The two haploid nuclei derived from the sperm and oocyte and contained within the egg are referred to as pronuclei. Anatomy and Physiology 2013-06-19T00:00:00Z In a haploid dominant life cycle, a multicellular haploid stage is present, as in plants. Biology for AP Courses 2022-06-09T00:00:00Z Spores produced by these plants grow into thin, heart-shaped haploid gametophytes, which live independently of the sporophyte. Miller & Levine Biology 2018-01-01T00:00:00Z Most fungi produce a large number of spores, which are haploid cells that can undergo mitosis to form multicellular, haploid individuals. Fundamentals of Biology 2015-01-01T00:00:00Z The resulting offspring can be either haploid or diploid, depending on the process in the species. Concepts of Biology 2013-04-25T00:00:00Z “The key innovation is using haploid inducer pollen as a sort of Trojan Horse,” says Kelliher, whose Syngenta-led team describes the system today in Nature Biotechnology. Corn and other important crops can now be gene edited by pollen carrying CRISPR 2019-03-04T05:00:00Z In alternation of generations, both haploid dominant and diploid dominant stages alternate, as in fungi. Biology for AP Courses 2022-06-09T00:00:00Z 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 Zygomycetes have a thallus of coenocytic hyphae in which the nuclei are haploid when the organism is in the vegetative stage. 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 “It is imaginative by combining two technologies: haploid induction and genome editing.” Corn and other important crops can now be gene edited by pollen carrying CRISPR 2019-03-04T05:00:00Z Spores are haploid reproductive cells that can produce diploid cells without fertilization. Biology for AP Courses 2022-06-09T00:00:00Z The authors tested the effect of inactivating the human versions of six of these genes in vitro in haploid cancer cells — cancer cells that contain only one copy of each gene. One rogue agent suffices for genomic chaos 2019-01-29T05:00:00Z In each ascus, two or more haploid ascospores fuse their nuclei in karyogamy. Fundamentals of Biology 2015-01-01T00:00:00Z Nearly all animals employ a diploid-dominant life-cycle strategy in which the only haploid cells produced by the organism are the gametes. Concepts of Biology 2013-04-25T00:00:00Z Using gene editing techniques, the scientists deleted three imprinting regions of the genome from haploid ESCs containing a female parent’s DNA and injected them into eggs from another female mouse. Scientists use stem cells and gene editing to make mice with two mums 2018-10-11T04:00:00Z 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 From those eggs, the scientists were then able to harvest stem cells that were haploid—meaning each contained only half the typical number of chromosomes, instead of a complete set from two parents. Same-Sex Mice Parents Give Birth to Healthy Brood 2018-10-11T04:00:00Z The sporophyte is diploid and the gametophyte is haploid. Fundamentals of Biology 2015-01-01T00:00:00Z Most fungi and algae employ a life-cycle strategy in which the multicellular “body” of the organism is haploid. Concepts of Biology 2013-04-25T00:00:00Z Making mice from two fathers was more complicated, the researchers said, and involved modifying haploid ESCs containing only a male parent’s DNA to delete seven key imprinted regions. Scientists use stem cells and gene editing to make mice with two mums 2018-10-11T04:00:00Z For instance, fertilization of an abnormal diploid egg with a normal haploid sperm would yield a triploid zygote. Biology for AP Courses 2022-06-09T00:00:00Z The yeast strains generated by the groups are haploid — they contain only one copy of each chromosome. Yeast chromosome numbers minimized using genome editing 2018-07-31T04:00:00Z The pollen tube develops slowly, and the generative cell in the pollen grain divides into two haploid sperm cells by mitosis. Fundamentals of Biology 2015-01-01T00:00:00Z The haploid multicellular plants are called gametophytes because they produce gametes. Concepts of Biology 2013-04-25T00:00:00Z Researchers are now starting to use gene-editing tools on these ‘haploid’ ES cells to understand how genes function in development. How human embryonic stem cells sparked a revolution 2018-03-19T04:00:00Z The human genome has three billion base pairs per haploid set of chromosomes, and 6 billion base pairs are replicated during the S phase of the cell cycle. Biology for AP Courses 2022-06-09T00:00:00Z 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 At fertilization, one of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of a haploid egg cell. Fundamentals of Biology 2015-01-01T00:00:00Z Meiosis is not involved in the production of gametes in this case, as the organism that produces gametes is already haploid. Concepts of Biology 2013-04-25T00:00:00Z “With doubled haploid, you basically fix those traits in a single generation.” Kansas researchers looking at new wheat varieties 2017-09-01T04:00:00Z After meiosis, four haploid spores are produced, which can germinate. Biology for AP Courses 2022-06-09T00:00:00Z The technical term for this is a haploid cell. ‘Motherless babies!’ How to create a tabloid science headline in five easy steps 2016-09-14T04:00:00Z Other protists have multicellular stages in both haploid and diploid forms, a strategy called alternation of generations that is also used by plants. 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 Sally = expression data from the double haploid fish used for reference genome sequencing. b, Classification of 11 co-expression clusters. The Atlantic salmon genome provides insights into rediploidization : Nature : Nature Publishing Group 2016-04-17T04:00:00Z The resulting offspring can be either haploid or diploid, depending on the process and the species. Biology for AP Courses 2022-06-09T00:00:00Z A next logical step in the research, Egli said, was to modify these haploid stem cells either to introduce new disease variances or correct those already there. Scientists grow human stem cells with genes of only one 'parent' 2016-03-16T04:00:00Z When the haploid spore germinates in a hospitable environment, it generates a multicellular gametophyte by mitosis. Fundamentals of Biology 2015-01-01T00:00:00Z They have the same number of sets of chromosomes: one in the case of haploid cells, and two in the case of diploid cells. Concepts of Biology 2013-04-25T00:00:00Z Sally = expression data from the double haploid fish used for reference genome sequencing. b, Classification of 11 co-expression clusters. The Atlantic salmon genome provides insights into rediploidization : Nature : Nature Publishing Group 2016-04-17T04:00:00Z Sperm are haploid cells, consisting of a flagellum as a tail, a neck that contains the cell’s energy-producing mitochondria, and a head that contains the genetic material. Biology for AP Courses 2022-06-09T00:00:00Z To avoid reporting both haplotypes at these loci, scaffolds with less than 6% divergence over at least 75% of their length were merged into a single haploid reference for comparative analysis. Hemichordate genomes and deuterostome origins : Nature : Nature Publishing Group 2015-11-17T05:00:00Z 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 These species have both haploid and diploid multicellular organisms as part of their life cycle. Concepts of Biology 2013-04-25T00:00:00Z Furthermore, while many SVs in our callset are statistically phased, the diploid nature of the genome is non-optimally captured by current analysis approaches, which mostly rely on mapping to a haploid reference. An integrated map of structural variation in 2,504 human genomes : Nature : Nature Publishing Group 2015-09-29T04:00:00Z Meiosis produces haploid cells with half of each pair of chromosomes normally found in diploid cells. Biology for AP Courses 2022-06-09T00:00:00Z Since the haploid moss — the gametophyte — likely evolved first, it still resembles green plants’ filamentous green algal ancestors. Mosses Make Two Different Plants From the Same Genome, and a Single Gene Can Make the Difference 2013-05-12T19:45:00.233Z A megaspore develops into a female gametophyte containing a haploid egg. Fundamentals of Biology 2015-01-01T00:00:00Z The approach to producing an artificially cloned individual is to take the egg cell of one individual and to remove the haploid nucleus. Concepts of Biology 2013-04-25T00:00:00Z The egg nucleus, now known as the female pronucleus, and each body contain the reduced or haploid number of chromosomes. Being Well-Born An Introduction to Eugenics 2012-05-22T15:16:53.140Z At the end of the first meiotic division, a haploid cell is produced called a secondary spermatocyte. Biology for AP Courses 2022-06-09T00:00:00Z The thing you think of as moss is actually the gametophyte — the haploid organism. Mosses Make Two Different Plants From the Same Genome, and a Single Gene Can Make the Difference 2013-05-12T19:45:00.233Z More complex chlorophyte species exhibit haploid gametes and spores that resemble Chlamydomonas. Fundamentals of Biology 2015-01-01T00:00:00Z Each of these gametes is haploid, meaning they contain one set of chromosomes in their nuclei. Concepts of Biology 2013-04-25T00:00:00Z Technically the tissue-cells are said to contain the diploid number of chromosomes, the gametes the reduced or haploid number. Being Well-Born An Introduction to Eugenics 2012-05-22T15:16:53.140Z This cell is haploid and must go through another meiotic cell division. Biology for AP Courses 2022-06-09T00:00:00Z Like the gametes they produce, the plants are haploid, that is, they contain one copy of all their chromosomes instead of two. Ferns, Secret Ninja Ferns, and their Alluring Asexual Bits 2012-05-07T11:15:00.827Z 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 Most plants exhibit alternation of generations, which is described as haplodiplontic: the haploid multicellular form known as a gametophyte is followed in the development sequence by a multicellular diploid organism, the sporophyte. Concepts of Biology 2013-04-25T00:00:00Z The resulting individual is normal in every respect except that instead of the usual diploid number it has only the single or haploid number of chromosomes. Being Well-Born An Introduction to Eugenics 2012-05-22T15:16:53.140Z The nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome. Biology for AP Courses 2022-06-09T00:00:00Z Our eggs and sperm are likewise haploid, while our bodies are diploid. Ferns, Secret Ninja Ferns, and their Alluring Asexual Bits 2012-05-07T11:15:00.827Z In a bryophyte, all the conspicuous vegetative organs—including the photosynthetic leaf-like structures, the thallus, stem, and the rhizoid that anchors the plant to its substrate—belong to the haploid organism or gametophyte. Fundamentals of Biology 2015-01-01T00:00:00Z One of the sperm cells will finally unite its haploid nucleus with the haploid nucleus of an egg cell in the process of fertilization. Concepts of Biology 2013-04-25T00:00:00Z One haploid, in particular, in the lower left quadrant, was orienting itself toward the haploid cell next to it. Yeast Genetics in ?The Marriage Plot? - Scientist Was Fiction, but Not His Work 2012-02-14T00:26:11Z Fertilization merges two diploid cells into a haploid cell. Biology for AP Courses 2022-06-09T00:00:00Z The normal number in the gamete, 7, is considered the simple or haploid number, and therefore the number 28 is called tetraploid. Hormones and Heredity The cycle starts with the release of haploid spores from the sporangium that developed on the sporophyte. Fundamentals of Biology 2015-01-01T00:00:00Z Only a single surviving haploid cell will develop into a female multicellular gametophyte that encloses an egg. Concepts of Biology 2013-04-25T00:00:00Z Those who do not possess the necessary special knowledge are unable to realise what remains of the first haploid generation in a phanerogamic plant or in a vertebrate animal. Darwin and Modern Science A diploid oogonium forms a haploid oocyte by the process of mitosis. Biology for AP Courses 2022-06-09T00:00:00Z Once the haploid gametes are formed, they lose the ability to divide again. 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 In animals, haploid cells containing a single copy of each homologous chromosome are found only within gametes. Concepts of Biology 2013-04-25T00:00:00Z The next stage is their separation to the haploid daughter-nuclei, which have resulted from the reduction process. Darwin and Modern Science A haploid oogonium forms a diploid oocyte by the process of meiosis. 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 The megasporangium contains megaspore mother cells, which divide by meiosis to produce haploid megaspores. Fundamentals of Biology 2015-01-01T00:00:00Z Gametes fuse with another haploid gamete to produce a diploid cell. Concepts of Biology 2013-04-25T00:00:00Z The haploid generation suffered a proportional reduction, until it finally ceased to have an independent existence and became restricted to the role of producing the sexual products within the body of the diploid generation. Darwin and Modern Science A diploid oogonium forms a haploid oocyte by the process of meiosis. Biology for AP Courses 2022-06-09T00:00:00Z Although haploid like the “parents,” these spores contain a new genetic combination from two parents. Biology for AP Courses 2022-06-09T00:00:00Z Some protists are unicellular in the haploid form and multicellular in the diploid form, a strategy employed by animals. Fundamentals of Biology 2015-01-01T00:00:00Z The nuclear division that forms haploid cells, which is called meiosis, is related to mitosis. Concepts of Biology 2013-04-25T00:00:00Z Species with alternation of generations have both haploid and diploid multicellular organisms as part of their life cycle. 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 The haploid multicellular plants are called gametophytes, because they produce gametes from specialized cells. Biology for AP Courses 2022-06-09T00:00:00Z The cells each exchange one of these haploid nuclei and move away from each other. Fundamentals of Biology 2015-01-01T00:00:00Z In a bryophyte, all the conspicuous vegetative organs belong to the haploid organism, or gametophyte. Concepts of Biology 2013-04-25T00:00:00Z Meiosis is not directly involved in the production of gametes in this case, because the organism that produces the gametes is already a haploid. Biology for AP Courses 2022-06-09T00:00:00Z Human cells that contain one set of chromosomes are called gametes, or sex cells; these are eggs and sperm, and are designated 1n, or haploid. Biology for AP Courses 2022-06-09T00:00:00Z In some plants, such as ferns, both the haploid and diploid plant stages are free-living. Biology for AP Courses 2022-06-09T00:00:00Z If this occurs, the spores germinate to form ameboid or flagellate haploid cells that can combine with each other and produce a diploid zygotic slime mold to complete the life cycle. Fundamentals of Biology 2015-01-01T00:00:00Z Some exceptions exist: For example, in bees, wasps, and ants, the male is haploid because it develops from an unfertilized egg. Concepts of Biology 2013-04-25T00:00:00Z The diploid plant is called a sporophyte because it produces haploid spores by meiosis. Biology for AP Courses 2022-06-09T00:00:00Z The spores develop into multicellular, haploid plants called gametophytes because they produce gametes. Biology for AP Courses 2022-06-09T00:00:00Z 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 The haploid spores germinate and give rise to the next generation of gametophyte. Fundamentals of Biology 2015-01-01T00:00:00Z The nuclear membranes of the egg and sperm break down and the two haploid nuclei fuse to form a diploid nucleus or genome. Concepts of Biology 2013-04-25T00:00:00Z Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition. Biology for AP Courses 2022-06-09T00:00:00Z Chromosomal crossover occurs during the mitotic process when chromosomes are linked together and recombination takes place, increasing the variance of genetic combinations in the haploid mitotic cells formed from mitosis. Biology for AP Courses 2022-06-09T00:00:00Z In a haploid dominant life cycle, a unicellular haploid stage is present, as in fungi. Biology for AP Courses 2022-06-09T00:00:00Z In bryophytes, such as mosses, the haploid gametophyte is more developed than the sporophyte. Fundamentals of Biology 2015-01-01T00:00:00Z In alternation of generations both haploid dominant and diploid dominant stages alternate, as in plants. Biology for AP Courses 2022-06-09T00:00:00Z Spores are haploid reproductive cells that can produce haploid organisms through mitosis. Biology for AP Courses 2022-06-09T00:00:00Z The union of these two haploid cells, one from each parent, is fertilization. Biology for AP Courses 2022-06-09T00:00:00Z Spores are haploid precursors to gametes that give rise to gametes when environmental conditions are favorable. 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 Somatic cells have 46 chromosomes and are haploid, whereas gametes have 23 chromosomes and are diploid. 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 Spores are haploid cells that can produce a haploid organism or can fuse with another spore to form a diploid cell. Biology for AP Courses 2022-06-09T00:00:00Z Two haploid cells are the end result of the first meiotic division. 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 The cells are haploid because at each pole, there is just one of each pair of the homologous chromosomes. Biology for AP Courses 2022-06-09T00:00:00Z This is why the cells are considered haploid—there is only one chromosome set, even though each homolog still consists of two sister chromatids. Biology for AP Courses 2022-06-09T00:00:00Z 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 Cytokinesis separates the two cells into four unique haploid cells. Biology for AP Courses 2022-06-09T00:00:00Z Some exceptions exist: for example, in bees, wasps, and ants, the male is haploid because it develops from unfertilized eggs. Fundamentals of Biology 2015-01-01T00:00:00Z At this point, the newly formed nuclei are both haploid. 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 In most animals, the diploid stage dominates, whereas in fungi, the haploid stage dominates. 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 Meiosis and fertilization alternate as the organisms pass through the haploid and diploid stages of their life cycles. 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 The haploid cells that make up the tissues of the dominant multicellular stage are formed by mitosis. Biology for AP Courses 2022-06-09T00:00:00Z Fertilization, the joining of two haploid gametes, restores the diploid condition. 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 Figure 11.10 Plants have a life cycle that alternates between a multicellular haploid organism and a multicellular diploid organism. Biology for AP Courses 2022-06-09T00:00:00Z Thus, crossover increases the variance of genetic combinations in the haploid gamete cell. Biology for AP Courses 2022-06-09T00:00:00Z |
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