BIOS 10161 Lecture Notes - Lecture 25: Sister Chromatids, Meiosis, Menstrual Cycle
Document Summary
Sexual reproduction: the offspring are not identical to the parents it requires gametes created by meiosis, two parents each contribute one gamete to an offspring: gametes and offspring differ genetically from eachother and from the parents. Somatic cells body cells not specialized for reproduction. Each somatic cell contains homologous pairs of chromosomes with corresponding genes: each parent contributes one homolog. Gametes contain only one set of chromosomes: haploid. Number of chromosomes = n: fertilization: two haploid gametes (female egg and male sperm) fuse to form a diploid zygote. Several kinds of sexual life cycle: diplontic life cycle animals and some plants; gametes are the only haploid stage. Mature organism is diplod and produces gametes by meiosis. Zygote divides by mitosis to form mature organism. Diplontic, diploid: alternation of generations (haploid and diploid stages both multicellular) most plants, some protists meiosis gives rise to haploid spores. Spores divide by mitosis to form the haploid generation (gametophyte)