PSYC 210 Lecture Notes - Lecture 3: Y Chromosome, Cell Nucleus, Twin
3 Dec 2017
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Document Summary
Mitosis: cell nucleus duplicated, cell divides - two cells formed. Meiosis: cell division that forms sperm and eggs (gametes) In females, the 23rd pair consists of two chromosomes called x chromosomes. In males, the 23rd pair consists of an x and a y chromosome. Each parent contributes half of child"s genetic material. Dizygotic twins (non-identical) - two eggs are fertilized. Mutated gene - a permanently altered segment of dna. Physical characteristics - height, weight, hair color, etc. In some cases, one gene of a pair is dominant. Recessive gene - may be overridden by a dominant gene. May be carried from generation to generation but not expressed in phenotype. When carried on the x chromosome - x-linked inheritance. Males have no backup copy to counter the harmful gene. Females have a second x chromosome, which is likely to be unchanged. Females who have one changed copy of the x gene are known as carriers
