Homologous chromosomes during meiosis

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hplc
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Homologous chromosomes during meiosis

Post by hplc » Thu Sep 04, 2008 1:17 pm

Hello.

I'm a first year biology student, and I'm currently reading a text-book on genetics and evolution. But there is a part about the meiosis I don't understand. According to the book, two sets of homologous chromosomes are inherited from each parent. But I can't understand how two random individuals of a given species have homologous chromosomes. Does all individuals in a given species have the same structural features in their genes? Or are the chromosomes made homologous during the meiosis process? I can't understand this.

Hope you can help me out! Thanks.

blcr11
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Post by blcr11 » Thu Sep 04, 2008 3:22 pm

Homologous doesn’t mean identical, if that’s what you think. And you inherit one chromosome from each parent to generate a set of homologous pairs of chromosomes for each offspring. The simplest answer is that, yes, within a species the homologous chromosomes have the same structure—with some slight but essential variations. Humans, for example, with rare exceptions all have 22 pairs of homologous autosomes and a pair of sex chromosomes. My pairs of chromosomes, one of which I inherited from my father and one from my mother, are homolgous: they are nearly—but not perfectly—identical. My wife’s chromosomes are likewise homologous, but, of course she inhereted hers from her mother and father. We have a daughter whose chomosomes are inherted half from me and half from my wife—which means that our daughter has inhereted roughly ¼ of her genes from each of her grandparents, and so on. And yet there is still plenty enough sequence identity between her chromosomes that I am confident that, when the time comes, her meiotic machinery will faithfully reassort the genes she inherited from my wife and I and that they will be fully homologous with the chromosomes our future grandchild will inheret from two other, as yet unknown, grandparents. My point is that there is plenty of sequence identity between the homolgous chromosomes of individuals within a species for meiotic recombination to occur.

hplc
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Post by hplc » Thu Sep 04, 2008 5:18 pm

Thank you for a helpful reply.

I know that the term homologous doesn't mean perfectly alike, but that the locus are positioned on the same place in a pair of chromosomes. So, this means that every individual within the same species have homologous chromosomes?

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Re: Homologous chromosomes during meiosis

Post by blcr11 » Thu Sep 04, 2008 5:45 pm

I think that's a fair statement. There are rare abnormalities, but even these don't change the homologous nature of the chromosomes.

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