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The Genetic Code BIOL 2401
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  • 1. The Genetic Code BIOL 2401 Central Texas College Chelsea Barker, MS
  • 2. Cell Reproduction
    • Necessary for continuation of life
    • Somatic cells divide to form two identical daughter cells with complete genetic codes through mitosis
    • Gamete cells divide to carry half of the genetic code (sperm and eggs) through meiosis
    • Cells grow and go through other living processes until division occurs again (cell cycle)
  • 3. Cell Cycle
    • Continual process of growth and division characterized in these steps
      • Interphase
      • Mitosis
        • Prophase
        • Metaphase
        • Anaphase
        • Telophase
    See Figure 3.35 in book.
  • 4. Interphase
    • Cell undergoes growth
    • Carries out its specified functions
    • Synthesis phase: DNA replicates
    • Growth phase: other structures are synthesized
  • 5. Mitosis
    • Prophase
      • Chromatin condenses into identical chromatids
    • Metaphase
      • Chromosomes align at the center along spindle fibers
    • Anaphase
      • Chromosomes separate and move to opposite ends of the cell along shortening spindle fibers
    • Telophase
      • Chromosomes are at each end and begin to uncoil
    • Citokinesis
      • Begins in anaphase where cell membrane begins to pinch off and continues through telophase
  • 6. Cell Cycle See Figure 3.36 in book.
  • 7. Genetic Information
    • Your genetic information contains instructions for cellular makeup through protein construction
    • Gene-a sequence of DNA that codes for a particular protein
    • Genome-entire set of genetic information
  • 8. Human Genome See figure 24.3 in the book.
  • 9. Base Pairing
    • DNA
      • Guanine-cytosine
      • Adenine-thymine
    • Purines: A & G
      • 2 rings
    • Pyridimines: T &C
      • 1 ring
    • RNA
      • Guanine-cytosine
      • Uracil-adenine
    *DNA is universal among species as a result of this base pairing. *Triplicates code for the same amino acid in all species.
  • 10. DNA Structure
    • Base pairs are aligned in a particular sequence
    • Hydrogen bonds hold base pairs together and phosphate bonds hold adjacent nucleotides
    • A “ladder” is formed and then twisted into a double helix
    • Double helix DNA--->chromatin---> chromatid--->chromosome
  • 11. DNA Structure See Figure 4.19 in book.
  • 12. DNA Replication
    • DNA must have an exact copy made so that each daughter cell has a full genetic code
    • Hydrogen bonds broken between base pairs
    • Free nucleotides link up with the opposing nucleotide making new hydrogen bonds using the enzyme DNA polymerase
    • DNA unwinds continuously to give two new double helix strands
  • 13. DNA Replication See Figure 4.20 in book.
  • 14. RNA Molecules
    • Messenger RNA (mRNA)
      • Formed through transcription (DNA to mRNA)
      • Each triplicate, called a codon, “codes” for an amino acid
      • mRNA takes the information outside the nucleus
    • Transfer RNA (tRNA)
      • Made of anticodons that match mRNA codons with amino acids attached
      • Transfers amino acids to mRNA and translates the codons of mRNA to specific amino acids to form proteins, a process known as translation
    • Ribosomal RNA (rRNA)
      • Provides enzymatic activity for ribosomes
  • 15. Codons See Table 4.2 in book.
  • 16. Protein Synthesis See Figure 4.23 in book.
  • 17. Protein Synthesis See Figure 4.24 & table 4.3 in book.
  • 18. DNA Mutation
    • Bases get exchanged in replication of DNA or translation of RNA
    • Some mutations are unnoticed
    • Some mutations are large and change cellular function/metabolism
    • Repair enzymes try to catch and correct mutations
    • Example: cancer
    See Figure 4.25 in book.
  • 19. Inheritance of DNA
    • Gametes (sperm and egg) receive only half of the full genetic code during the division
    • A full genetic code is restored when egg and sperm meet
    • The paring up and unique set is obtained based on what “half” of each parent’s genetic code is passed on
  • 20. Punnett Square X X X Y MOM DAD XX XX XY XY
  • 21. Genotype vs. Phenotype
    • The genetic make up of the individual for a specific trait
    • Expressed by letters
      • BB-2 dominant genes
      • Bb- 1 dominant, 1 recessive gene
      • bb-2 recessive genes
    • The expression of the genetic make up of a trait in an individual
    • Expressed by letters
      • BB-Brown eyes
      • Bb-Brown eyes
      • bb-Blue eyes
    • Homozygous: same
      • Dominant: BB
      • Recessive: bb
    • Heterozygous: different (Bb)
  • 22. Punnett Square Practice
    • Male or female child?
      • X-female, Y-male
      • XX (mom) with XY (dad)
    • Widows Peak?
      • P-widows peak (dominant), p-straight (recessive)
      • Mom-widows peak (Pp) and Dad-straight (pp)
    • Flower color in plants?
      • C-red, c-white & can co-express to give pink (Cc)
      • Red flower (CC) and a white flower (cc)