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Ideally, DNA itself is the same in DNA-containing cell types. Cell type depends on expression, which depends on epigenetics. I.e. histone modification, DNA methylation, and few other mechanisms. Also, epigenetics is the mechanism for gene expression regulation. For example, it can silence (usually, methylate promoter regions) an expression of genes on one ...


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One or both pairs of homologous chromosomes could exchange genetic material during the process of crossing over. The number of cross-over events depends on the number of chiasmata. There are also ways for meiosis to occur with no exchange of genetic material between homologous chromosomes. The image you reference at uic.edu is incorrect. The purple arms ...


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Most cells in a human body contain a complete set of the genome, which is two sets of 23 chromosomes. Having two of each chromosome is called diploidy. Within an individual human the DNA is approximately identical in every cell. Different cells are produced by differential use of that DNA: certain genes are more (or less) highly expressed etc. You can read ...


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It's strongest in the breeding season but male-male competition exists outside of the breeding season too, e.g. European Robins only breed in the summer, yet maintain territories year-round. It's pretty circumstantial, however sexual competition will only exist in the breeding season. To address the Red Deer example, the deer only compete with antlers in ...


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Infertility is defined as the inability to conceive after one year or longer of intercourse without the use of contraception or therapeutic donor artificial insemination. That definition does not include a state of permanence. That is, with treatment, fertility can indeed be achieved in many cases. You may want to consider the term sterility as a ...



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