BIO 322 PSU Cell Division and Chromosome Heredity Questions and Correct Answers

Mitosis Cell division process which produces two genetically identical daughter cells from a single original parental cell. Genetically controlled process. First: Interphase Followed by: M phase Interphase G1: Active gene expression and cell activity; preparation for DNA synthesis. G0: Terminal differentiation and arrest of cell division. S phase: DNA replication and chromosome replication. There is a single DNA helix per chromatid. DNA replication during S phase results in sister chromatids held together by a common centromere. G2: Preparation for cell division. M phase: Cell division: i) Mitosis: Somatic cells. ii) Meiosis: Germ-line cells. Karyokinesis equal partitioning of the chromosomal material in the nucleus of the parental cell between the nuclei of the two daughter cells. Cytokinesis partitioning of the cytoplasmic contents of the parental cell into the daughter cells. M phase (Mitosis) 2n at the start and 2n at the end. a) Prophase: Chromosomes start to condense. Mitotic spindles start to form. Nucleolus disappears. b) Prometaphase: Chromosomes have finished condensing-so, they are compact. The nuclear envelope breaks down, allowing the release of chromosomes. The mitotic spindle grows more, and some of the microtubules start to "capture" chromosomes. c) Metaphase: All the chromosomes align at the metaphase plate. The two kinetochores of each chromosome should be attached to microtubules from opposite spindle poles. d) Anaphase: Sister chromatids are held together by cohesion protein until the start of anaphase where separase breaks down cohesion. The separation of sister chromatids in anaphase is called chromosome disjunction. e) Telophase: The mitotic spindle is broken down. Two nuclei are formed. Nuclear membrane and nucleoli reappear. The chromosome begin to decondense. May or may not be followed by cytokinesis. Meiosis I Production of gametes: 2n -> n