BIOL308 Lecture Notes - Lecture 9: Dna Replication, Sexual Reproduction, Gamete
16 Jul 2014
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Document Summary
A fundamental problem - a paradox - for nature, re genetics: How to preserve the information while keeping/making it variable at the same time? as variability is very important for survival if life/environmental conditions change. Resolution of the paradox through sexual reproduction and meiosis. Production of special reproductive cells, or gamete (1n) Gametes produced in specialized tissues through reductional (2n-->n) cell division=meiosis. Reduction of chromosome number - only one round of chromosome (dna) replication = one duplication of genetic material, but two meiotic divisions. Homologous chromosomes, containing duplicated dna, separate (2n --> n) Homologous pair of chromosomes in diploid parent cell. Note: chromosome 21 is derived due to nondisjunction occurring at meiosis-ii and chromosome x due to meiosis-i. it has also been interpreted that both non disjunction events have occurred in the mother. Variability 1: the independent assortment of homologous chromosomes in meiosis. Two equally probable arrangements of chromosomes at metaphase i.
