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Inheritance160-page8 - By the early 1900's it was known...

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Inheritance Patterns - 8 Crossing over during meiosis results in the exchange of bits and pieces of DNA between homologous pairs of chromosomes at the chiasmata during prophase I of meiosis. This process of recombination results in sister chromatids and gametes (or meiotic products) that are not identical; some of the linkage groups have been changed by the crossing-over. As a result of recombination, new allele combinations are formed, and we have more genetic variation. Crossing Over and Recombination Chromosomes in gametes Sex-Determination and Sex-Linked Traits One of the earliest discoveries about gene linkage related to another significant thing about chromosomes and species, especially animal species.
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Unformatted text preview: By the early 1900's it was known that males and females of most species have one pair of "not-exactly-matching" homologous chromosomes, which determined the gender of the individual. These chromosomes were called the sex chromosomes. (The truly matching chromosomes are the autosomes.) With the sex-determining chromosomes, one sex, usually female, will have two matching chromosomes (XX) and the other sex will have two unmatched chromosomes (XY). At meiosis, all eggs will contain an X chromosome, but half the sperm gametes will have a Y chromosome and the other half will have an X chromosome....
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