BIOL 150 Lecture Notes - Lecture 27: Homologous Chromosome, S Phase, Monosomy
Document Summary
Biol 150 principles of molecular & cellular biology. Review of cell division, basics of dna replication. We reviewed the processes of mitosis and meiosis, with a special emphasis on understanding the number of sets of chromosomes and number of chromatids/chromosomes. Most of our cells are diploid, having 2 sets of chromosome (one from mom, one from dad). Before s phase, each chromosome has 1 chromatid; after dna replication (s-phase), each chromosome has twice as much dna since each chromosome now has 2 chromatids. You still have the same number of chromosomes (2n) as before, but the chromatids have been duplicated. The key step in mitosis is anaphase, where the microtubules pull the two halves of the chromosome apart to bring one set of chromosomes (each with just 1 chromatid) to each side of the parent cell. After cytokinesis, each of the 2 new cells will have 2n chromosomes (1 set from dad, 1 set from mom) that are not duplicated.
