BIO_SC 1200 Lecture Notes - Lecture 1: Sister Chromatids, Megaspore, Plant Reproduction
15 Jan 2015
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Process to make gametes (eggs and sperms) in animals and spores in plants. Reduces chromosome number from diploid to haploid: diploid (2n) two copies of each chromosome, haploid (n) one copy of chromosomes. 1 diploid cell produces four haploid cells \ Increases diversity: crossing over dna sections are exchanged by homologous chromosomes, random assortment each gamete gets 1 of the homologous chromosomes. Three major steps: dna replications (same as cell division, 1st cell division homologous chromosomes separate. Each cell is diploid, but the chromosomes don"t separate from their x shape. Crossing over and random alignment occur: 2nd cell division sister chromatids (1 copy of a dna molecule) separate. Happens in the flowers of angiosperms: ovule is the female part of the flower. Diploid cell undergoes meiosis to produce 4 haploid megaspores. Diploid cells undergo meiosis to create 4 haploid microspores. Mitosis divides the nucleus in each microspore. Generative nucleus divides to make two sperm nuclei (male gametes)
