BIOL308 Lecture 10: Lecture 10
8 Apr 2016
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Document Summary
Occur throughout cell cycle; assess & control readiness of cell to proceed. Several events (internal and external signals) can trigger checkpoints. Cycle arrested e. g. , check for dna damage at every stage. A fundamental problem - a paradox - for nature, re genetics: Variability is very important for survival if any conditions change. Resolution of the paradox through sexual reproduction and meiosis. Sexual reproduction: production of special reproductive cells, or gamete (1n, fusion of gametes (fertilization) zygote (2n) Gametes produced in specialized tissues through reductional (2n n) cell division = meiosis. Zygote (b) plants and some algae (c) most fungi and some protists. Homologous pair of chromosomes in diploid parent cell. Only one round of dna replication (= one duplication of genetic material), 1. homologous chromosomes, containing duplicated dna, separate (2n n) Two equally probable arrangements of chromosomes at metaphase i. The number of possible new combinations of chromosomes for a species is 2n.
