DNA Chromosomes (half of 2.4)

• Chromosomes

  Genetic structures occurring in functional pairs in the nucleus of cells except gametes and bacteria
• Genes


  Sections of chromosomes made up of short lengths of DNA that operate as functional units to control characteristics
• Alleles


  Different forms of the same gene
• Genome


  The entire genetic material of an organism
• Double helix


  A phosphate and sugar backbone with interlinking bases form a double helix
• Base pairing rules


  • A = adenine
  • T = thymine
  • C = cytosine
  • G = guanine
• Complementary base pairings


  A is complementary to T and C is complementary to G they pair up
• Nucleotide


  Consists of 1 phosphate, 1 sugar, and 1 base
• DNA


  Providing a code for cells to make a particular protein
• Base triplet hypothesis

  1. Three bases (a base triplet) code for one amino acid.

  2. Amino acids are then joined in this order to make the protein.
• Types of cell division

  • Mitosis
  • Meiosis
• Mitosis


  • Used to grow, replace worn-out cells, and repair damaged tissue

  Produces two new cells (daughter cells) that are genetically identical (clones) to the parent cell and each other
• Meiosis


  • Only occurs in the testes and ovaries, producing gametes (sperm and egg cells)

  One diploid cell produces four haploid gametes, in two divisions

  The four gametes produced are genetically different
• Human sex cells contain one chromosome from each of the 23 pairs
• Independent assortment reassorts the chromosomes to provide variation