Mitosis, Meiosis, DNA, Cell cycle

Replication Proceeds from 5’ to 3’ Occurs in the nucleus Occurs during interphase Is semiconservative Requires enzymes

Enzymes DNA polymerase: attaches new nucleotides DNA Iigase: joins 3’ end of one Okazaki fragment to the 5’ end of another Okazaki fragment. Helicase: Breaks hydrogen bonds, opens the zipper Topoisomerase: facilitates unwinding and unzipping of DNA

Haploid and diploid Haploid (n): after meiosis 1 chromosome from each pair Diploid (2n): somatic cell, zygote 2 chromosomes from each pair Beginning of meiosis 4 chromosomes from each pair 2 x diploid number

Cell cycle Interphase: most time Prophase: chromosomes condense Metaphase: replicated chromosomes line up on the equatorial plate Anaphase: pairs separate to opposite poles Telophase: New nuclei form Cytokinesis: cell divides

Cancer Tumor, Benign, Malignant, Metastatic High rate of mitosis Shorter cell cycle Poor or “broken” cell regulation

Enzymes

DNA

Electrophoresis Electric current pulls DNA toward the positive lead. What about DNA causes it to move to the positive end?

Avery, MacCleod, and McCarty

Avery, MacCleod, and McCarty Heat treating and protein degrading enzyme break down protein DNAase breaks down DNA

Crossing over Produces recombinations % recombination = map distance Increases genetic variability in gametes

Nondisjunction Tetrads fail to separate during anaphase II Can produce trisomy or monosomy

DNA Chargaff Watson Crick Adenine = Thymine Cytosine = Guanine Adenine is complimentary to Thymine Cytosine is complimentary to Guanine

Possibilities Number of gamete possibilities = 2n, where n = number of homologous chromosome pairs For humans 8,388,608 possible combinations

Mitosis and meiosis Mitosis produces copy (2n) Growth and repair Meiosis produces half a copy (n) Gametes Sperm Egg and polar bodies