MadSci Network: Genetics |
Humans have 23 pairs of chromosomes (DNA). Basically each chromosome is made up of small regions coding for a certain trait (ex: black hair). Alternate forms of traits are either recessive, dominant or neutral. So if the mother gives a dominant gene form (X) to her offspring (ex: for black hair)and the father gives a recessive gene form (x)for blonde hair, then the offspring will be Xx at this trait. Because X is dominant to x, this means the offspring will express the X version of the trait (black hair), not the x version (blonde hair). If the combination xx would occur then the offspring has a recessive trait x (blonde hair). ex: X dominant = black hair ; x recessive = blond hair XX = black hair Xx = black hair xx = blond hair Now you might want to read about meiosis to understand how the male and woman only give 23 chromosome each to the offspring during the fertilization process.
Try the links in the MadSci Library for more information on Genetics.