01:119:100 Lecture Notes - Lecture 5: Sister Chromatids, Homologous Chromosome, Synaptonemal Complex
12 Jul 2015
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Types of reproduction: asexual single parent produces offspring ex: spits, buds, fragment. Organisms well-adapted to environment produce lots of progeny. 1haploid(n) parent 2 haploid offspring: sexual reproduction, union of gametes(sex cells) forms a zygote. Offspring=not genetically identical to either of parents: problem--- if gametes had same number of chromosomes as parents then zygotes would have double chromosome number, solution meiosis. Chromosome number: somatic cell in higher plants and animals. 2 sets of chromosomes; one set from father one from mother diploid(2n) Homologous pairs: gametes always haploid(n) 1 set of chromosomes. Tunko islam: zygotes are always diploid 2n, 2 sets of chromosomes humans = Interphase- chomosomes duplicate, centrioles duplicated, each chormosomes consists of 2 sister chromatids. Prophase i: synapsis- homologous chromosomes align and pair up, one is maternal homologue, and paternal homologue. Synaptonemal complex forms, protein structure tetrad 4 member structure(4 chromatids: crossing over- enzymes break and rejoin dna molecules. Breaking and rejoining occur between non-sister homologous chromatids.
