Basic DNA and Genetics

Basic (like Elaine) DNA Double helix shape (Rosalind Franklin, Watson and Crick) DNA is wound around histone proteins to form chromatin During replication, supercoiling occurs Replication occurs during S phase of cell growth Leading strand and lagging strand Built 5’ to 3’ end

Replication in Depth DNA is first unwound at replication forks by helicase Stabilized by SSBPs Nucleotides are brought in to match template strands Arrive as nucleosides (DNA bases with triphosphate) Bound to the parent strand by DNA Polymerase III Can only add to 3’ end, so the strand grows from 5’ to 3’ Leading strand vs. Lagging strand Okazaki fragments and ligase DNA polymerase III can only add to existing: need RNA primer Primase Primers removed by DNA Polymerase I

Replication in Depth Telomeres are expendable, non-coding ends Telomerase (application to cancer) Though DNA pairs are matched pyramidine to purine, errors can occur, resulting in mutations Checked by DNA Polymerase I, but can fail End daughter cells both have same number of chromosomes as parent in MITOSIS (different in meiosis) Diploid vs. Haploid – alternation of generations

Genetics Gregor Mendel Genotype vs. Phenotype Punnett Squrrr Pea plants – good choice Crossed true-breeding parents (P) Crossed F1 generation again Noted masked traits resurfaced in the F2 generation Dominant vs. Recessive Allele Genotype vs. Phenotype Punnett Squrrr

Genetics Test Cross Mendel’s Laws of Segregation Determine genotype of a organism by crossing the dominant phenotype with a homozygous recessive Mendel’s Laws of Segregation #1 – Law of Segregation When gametes are produced, homologous chromosomes separate Created by meiosis I Monohybrid crosses #2 – Independent Assortment Each pair of alleles segregates into gametes independently Created by Meiosis I Dihybrid crosses (or more than 2 traits)

Human Genetics Pedigrees Diseases are recessive -> non-functioning protein (or lack of) Heterozygotes for the trait are referred to as “carriers” CF Extracellular buildup of Cl- ions, resulting in thick mucus Percussive treatment Tay-Sachs “Hitler’s Revenge” Enzyme that breaks down lipids in the brain is non-functional

Human Genetics Sickle Cell Anemia African Americans are primary afflicted Substitution in hemoglobin causes crystallization Pleiotropic Heterozygote advantage