How does crossing over during meiosis provide a source of genetic variation
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Meiosis is the process by which most eukaryotic organisms, those with cells having an organized nucleus, produces sex cells, the male and female gametes. Cells normally have two copies of each chromosome, one donated from each parent. This is the diploid chromosome condition and the paired chromosomes are called homologous. Meiosis transforms a diploid cell into four haploid granddaughter cells, each having a single copy of each chromosome. The process helps increase the genetic diversity of a species. Show
Meiosis I and IIMeiosis occurs over two generations of cells. During normal cell division, or mitosis, each chromosome is copied, resulting in chromosomes containing twin sister chromatids. These joined chromatids later separate in mitosis to form the next generation of identical chromosomes. In meiosis I, the chromatids do not separate, which means each daughter cell receives only one copy of each chromosome, the haploid number, and each copy contains two chromatids. In meiosis II, the chromatids separate and are distributed to each resulting gamete. Crossing OverDuring prophase of meiosis I, the double-chromatid homologous pairs of chromosomes cross over with each other and often exchange chromosome segments. This recombination creates genetic diversity by allowing genes from each parent to intermix, resulting in chromosomes with a different genetic complement. The exchange occurs between non-sister chromatids. Because genes often interact with each other, the new combination of genes on a chromosome can lead to new traits in offspring. Reduction to HaploidBecause the duplicated chromatids remain joined during meiosis I, each daughter cell receives only one chromosome of each homologous pair. This reduces the diploid number to haploid, and the distribution of each chromosome is random. This means that it is equally likely for a given chromosome to be distributed to either of the two daughter cells. By shuffling the genetic deck in this way, the gametes resulting from meiosis II have new combinations of maternal and paternal chromosomes, increasing genetic diversity. Random Chromatid AssortmentA third source of genetic diversity occurs during meiosis II, in which the sister chromatids separate and are randomly distributed to the daughter cells, the gametes. Crossing over in meiosis I leads to non-identical chromatids in meiosis II chromosomes. During anaphase of meiosis II, the centromere joining each chromatid pair dissolves, creating two chromosomes of each type. The outcome of which chromosome will go to which gamete is random, so that each gamete has a potentially unique combination of genetic material. FertilizationFertilization creates genetic diversity by allowing each parent to randomly contribute a unique set of genes to a zygote. While fertilization is not part of meiosis, it depends on meiosis creating haploid gametes. The fertilized cell restores the diploid number. Without meiosis, the number of chromosomes per cell would double in each generation of offspring, leading to unstable conditions that could threaten the viability of a species. References
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Writer Bio Based in Greenville SC, Eric Bank has been writing business-related articles since 1985. He holds an M.B.A. from New York University and an M.S. in finance from DePaul University. You can see samples of his work at ericbank.com. Independent assortment of homologous chromosomes leading to different genetic combinations in daughter cells Exam TipSeveral sources of genetic variation have been outlined above. It is also worth remembering that genetic variation can occur on an even smaller scale than chromosomes. Mutations can occur within genes. A random mutation that takes place during DNA replication can lead to the production of new alleles and increased genetic variation. Fusion of Gametes
 How meiosis and the random fusion of gametes affects genetic variation Exam TipThese sources of genetic variation explain why relatives can differ so much from each other. Even with the same parents, individuals can be genetically distinct due to the processes outlined above. Why does crossing over create genetic variation?Crossing over is important for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical.
How does crossing over during meiosis contribute to genetic variation quizlet?Explain how crossing over in meiosis results in genetic variation. In crossing over, genetic information is exchanged between homologous chromosomes. This exchange creates new combinations of genes, leading to increased genetic variation in the offspring. Both alleles are for the dominant trait.
In what 2 ways does meiosis provide genetic variation?During meiosis I, the random orientation of the maternal and paternal chromosomes can lead to variation. The exchange of genetic information between homologous chromosomes also induces variation. The random orientation of sister chromatids in meiosis II also generates genetic variation.
What are 3 ways meiosis allows for genetic variation?The three main sources of genetic variation arising from sexual reproduction are: Crossing over (in prophase I) Random assortment of chromosomes (in metaphase I) Random fusion of gametes from different parents.
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