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Introduction to Genetics. -the DNA molecule -nucleotides -chromosomes vs genes -DNA replication -cell division. The DNA molecule. Composed of 2 polymers of nucleotides Polymers are oriented in antiparallel Molecule resembles a spiral staircase of complementary base pairs.

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introduction to genetics

Introduction to Genetics

-the DNA molecule

-nucleotides

-chromosomes vs genes

-DNA replication

-cell division

the dna molecule
The DNA molecule
  • Composed of 2 polymers of nucleotides
  • Polymers are oriented in antiparallel
  • Molecule resembles a spiral staircase of complementary base pairs
nucleotide structure of dna
Nucleotide structure of DNA
  • Each nucleotide of DNA contains:
    • Deoxyribose
    • Phosphate
    • Nitrogen base (either A, G, C, T)
nucleotide structure of rna
Nucleotide structure of RNA
  • Each nucleotide of RNA contains:
    • Ribose
    • Phosphate
    • Nitrogen base (either A, G, C, U*)

*contains Uracil instead of Thymine

dna structure
DNA structure
  • “Double helix” propsed by Watson and Crick (1953)
  • Antiparallel backbones
  • Complementary base pairing:
    • Adenine to Thymine
    • Cytosine to Guanine
chromosomes vs genes
Chromosomes vs Genes
  • A chromosomeconstitutes an entire DNA molecule + protein
    • Protein = histones
    • Supercoiled DNA in nucleosomes
    • Humans contain 46 such molecules (23 pairs)
      • 44 somatic chromosomes
      • 2 sex chromosomes (X +Y)
chromosomes vs genes8
Chromosomes vs Genes
  • Genes constitute distinct regions on the chromosome
  • Each gene codes for a protein product
  • DNA -> RNA-> protein
  • Differences in proteins brings about differences between individuals and species
how do chromosomes become double stranded answer dna replication
How do chromosomes become double stranded?Answer: DNA replication
  • During the life of the cell, each chromosome of DNA makes a copy of itself
  • This must occur prior to cell division to insure each daughter cell gets a complete set
therefore prior to dividing any cell must first replicate dna
Therefore, prior to dividing, any cell must first replicate DNA
  • Each single-stranded (SS) chromosome duplicates to become a double-stranded (DS) chromosome
  • Example:
    • A human cell is formed with 46 SS chromosomes
    • Each chromosome replicates to produce 46 DS chromosomes
dna replication occurs during the life of a cell the cell cycle
DNA replication occurs during the life of a cell = the Cell Cycle
  • DNA replicates (makes a copy of itself) to produce DS chromosomes
  • During this time, the cytoplasmic contents also duplicate
  • Spindle tubules form to aid in the process of cell division
    • Mitosis in body cells
    • Meiosis in sex cells
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