Cellular control

Cyclic AMP activates proteins by altering their 3D structure.
Mutations cause changes in the sequence of nucleotides in DNA molecules.
Explain the meaning of the term genetic code
1. This is the sequence of bases
  1. 3 bases code for an amino acid.
2. A degenerate code is when there are more codes than animo acids.
Genes code for polypeptides, including enzymes.
Explain how mutations can have a benefitial,neutral or harmful effects on the way a protein functions.
1. Substitution/point
  1. Nonsense?
    1. Results in a stop codon.
  2. Missense?
    1. Results in a different amino acid.
  3. Silent?
    1. Results in no change.
  4. Neutral?
    1. Results in an allele.
2. Frameshift
  1. Addition or deletion of a base.
Describe the sequence of nucleotides withing a gene to construct a polypeptide.
1. Transcription
  1. Sections of DNA unwind and unzip.
  2. DNA helicase breaks the hydrogen bonds.
  3. Free RNA nucleotides diffuse into position.
  4. RNA nucleotides bind to the template strand, with hydrogen bonds and their complementary bases.
  5. Condensation reaction catalysed by RNA polymerase.
  6. Extra phosphate groups are released: ATP.
  7. mRNA is complementary and released through the nuclear pore.
2. Translation
  1. mRNA binds to a ribosome via complementary base pairing, two codons are attached to the ribosome.
  2. First codon is always AUG (start codon) and using ATP and an enzyme, tRNA with methaine and anticodon forms hydrogen bonds.
  3. Second tRNA binds and a peptide bond can be formed.
Explain genetic control of protein production in a prokaryote using the lac operon.
1. Promoter
  1. The enzyme RNA polymerase binds and so transcribes the operon.
2. Operator
  1. The body site for protein repression stops RNA polymerase getting to the protein.
3. Regulator
  1. Structural gene for the operator.
4. Operon
  1. Length of DNA that controls the switching on and off the structural gene.
  2. Required for the transport and metabolism of lactose in E. Coli.
5. Lactose is absent
  1. Regulator gene transcribes and translates the repressor protein.
  2. Repressor protein binds to the operator region and blocks the promoter region.
    1. RNA polymerase can't bind to the promoter region.
6. Lactose is present
  1. Binds to the repressor protein and this means that the protein cannot bind to the operator region.
  2. RNA polymerase binds, produces Beta Galactosidase and lactose permease which can convert the lactose into glucose.
Explain that the genes that control development of body plans are similar in plants, animals and fungi
1. Body plan is the general sequence of an organism.
2. Homeotic genes control body plan.
3. Highly conserved throughout phylogeny and change often results in extinction.
4. Code for transcription factors which are proteins.
5. Binds to DNA.
Outline how apoptosis can act as a mechanism to change body plans.
1. Apoptosis is programmed cell death.
2. Necrosis is unintentional cell death.
3. Enzymes breakdown the cytoskeleton, DNA and proteins.
4. Engulfed by phagocytes and lysosomes.

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