Biology 3592A Midterm: Pre-Midterm Key concepts.doc
13 May 2013
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Linear & circular chromosomes inside nucleus & mitochondria. Stored as genes through gene expression & meiosis (gametes) 37. 5% histones (h1, h2a, h2b, h3, h4) organization of nucleosomes + compaction of dna. 3 x 10^9 nucleotide base pairs (33% unique/single + 66% repetitive) Mitosis = new identical daughter cells = somatic cells. Meiosis: gametes (also go through mitosis to grow) Leptotene: unpaired with tightly bound sister chromatids. Diplotene: homologs separate but held by chiasmata. Law of segregation: alleles of same trait separated into different gametes. Law of independent assortment: alleles of different traits separated into different gametes, 8. 4 million different ways 23 chromosomes pairs separate. Linked: genes close together, travel together through meiosis. Meiosis i, pachytene crossing over between maternal and paternal homologs = variation, genetic diversity (results: 2 parental + 2 recombinants) On average each chromosomes = 2-3 cross over. Only one round of replication per 2 cell divisions (meiosis i & ii)
