Gene Expression

Gene Expression

Proteins
1. Fibrous
  1. Structure
2. Globular
  1. E.g. Enzymes or hormones
3. Coded by genes
  1. Gene is a section of DNA
Transcription
1. FIrst stage of protein synthesis
2. Occurs in the nucleus
3. DNA unwinds + unzips
  1. Coding strand
    1. identical to mRNA strand, except T instead of U
  2. Template strand
    1. 3 bases called triplet
    2. code for mRNA strand
      1. 3 bases called codon
      2. processed
        introns are removed
        exons are joined to together
        mRNA leaves the nuclues
        translation begins
      3. using complementary base pairing rule
        instead U replaces T
4. PURPOSE: mRNA transcribes the code for a polypeptide chain from the DNA. so the original DNA does not get damaged
Translation
1. mRNA enters cytoplasm and moves to the ribosome
  1. the ribosome moves along the mRNA reading the code
    1. the tRNA pairs with the mRNA
      1. using complementary base pairing rule
      2. the mRNA acts as a code for the tRNA
      3. the tRNA as an amino acid joined
        the coded for amino acids join together by peptide bonds
        forming a polypeptide chain
        A stop codon is read
        the polypeptide chain is released into the cytoplasm
        folds up in a particular way to produce a fuctional protein
        the protein is used fro cellular functions
      4. 3 bases on tRNA is called anti-codon
2. PURPOSE: to use the mRNA to make a polypeptide chain/protein. so the protein can be used for cellular functions
Mutations
1. A change in the DNA base sequence
2. can be harmful or helpful
3. Somatic mutation
  1. mutation in body cells, cannot be inherited
4. Gametic Mutation
  1. mutation in gametes, can be inherited by offspring
5. Mutagen
  1. causes mutations
    1. e.g. UV light, chemicals
6. Deletion
  1. A base is deleted
    1. Frameshift
      1. Making the reading of the triplets change along one.
      2. the following triplets affected, resulting in different amino acids
      3. different coded for protein or unfunctional protein
7. Insertion
  1. A base is inserted
8. Substitution
  1. one base swapped for another
  2. Missense
    1. changes the amino acid
  3. Nonsense
    1. changes the amino acid to a stop
  4. silent
    1. does not change the amino acid
      1. no affect on protein
      2. due to redundancy due to degeneracy
        more than one codon codes for the same amino acid
        e.g. UUU and UUC, both code for Phe
Metabolic Pathway
1. Linked biochemical reactions controlled by enzymes that maintain life processes in organisms
2. the reactants of one reaction are the products for the previous reaction
3. mutation occur may result in a enzyme not being produced or too much
  1. causing a build up of one product
    1. phenotype may be affected
Environmental Influences
1. genotype + environment ------> phenotype
2. temperature
3. light
4. moisture
5. minerals
6. nutrients

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	Created by georgia_rae over 9 years ago