Ask A Scientist© Biology Archive

name        Frank
status      student
age         30s

Question -  Could you explain why we could be similar in appearance to
our parents but not resemble either one exactly?
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Because of the process of meiosis or gamete formation (ie. the formation of
eggs and sperm). A human being has 46 chromosomes in each cell. We all
started out as one cell with 46 chromosomes, 23 came from mom and 23 from
dad. During egg and sperm formation, only half of the chromosomes make it
into an egg or a sperm. If this didn't happen, each succeeding generation
would have double the chromosome number its parents had. So, only half the
traits make it into an egg or a sperm also. Which half is random. Also, you
are half your mother (her egg) and half your father (the sperm). You must
also take into consideration dominance vs. recessiveness. When each parent
contributes a version of a trait, sometimes one gives a dominant form and the
other gives the recessive form. The recessive form of the trait is hidden by
the dominant one. Some offspring look more like one parent or the other
because one contributed more dominant traits than the other at random. By
mixing up the genetic material in the process of meiosis this allows a
species to "try out" new combinations and also to be able to adapt to new
environments.

Van Hoeck
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