CHYS 1F90 Lecture Notes - Meiosis, Trin, Miosis
21 Oct 2011
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Document Summary
Father"s sperm + mother"s ovum = zygote with 46 chromosomes in total. First 7-14 days it can survive on its own. The process by which a cell separates chromosomes in its nucleus into two identical cells. Chromosomes within sperm cells divide in half before they fertilize an ovum or egg cell. Chromosomes with egg cells divide in half before they are fertilized. The randomness creates variation in the resulting embryo. Direct production of amino acids necessary for forming new cells. Guide cells to develop different parts of body. May turn on or turn off other genes. Simple dominant recessive inheritance some alleles are stronger than others. To express a trait one must have a homozygous recessive allele. One gene is dominant and one is recessive. Dominant genes are almost always stronger than recessive genes. Some are not, and some babies are born with +1 or -1 chromosome or a genetically-based disease. Down syndrome (trisomy 21) most common extra 21st chromosome.
