BIO270H1 Lecture 6: Lecture 6 2012.pdf
Document Summary
Production of offspring from two parents that contribute nearly equal amounts of genetic material. Life cycle begins with a single cell. Sex determination acquisition of primary sex characteristics (gonad formation) Three sources of genomic variation: haploid gametes from a diploid parent. Spermatogenesis in males (sperm: oogenesis in females (ova, recombination creates hybrid chromosomes, diploid offspring unique genetic combinations. Fertilized eggs become diploid females and unfertilized eggs become haploid males. Temperature of egg incubation alters sex of offspring. Pivotal temperature - equal numbers of males & females result. May also be affected by hormone levels in egg - vary with season. Advantageous for animals living in constant, stable environment. Allows single individual to produce a colony. Negative (and positive) feedback controls on hormone synthesis. Target tissues can alter number of receptors. Males and females of same species may use same hormones, although specific hormones may have sex-specific functions.
