BIO 12 UNIT 2: Study Notes
PROTEIN SYNTHESIS
- Mutations and their effects:
- Definition: A change in the base sequence of DNA
- Causes: Radiation exposure and chemicals [Mistakes in base pairing during P.S.]
- TWO MAIN TYPES:
- Point: Single nucleotide base changes in a gene's DNA sequence
- MISSENSE- single amino acid change within the protein (ex. sickle red blood cell; body not able to make blood as effectively and many gain fatal diseases; TGT --> TGG is Cys --> Trp)
- NONSENSE- create a premature "stop" codon creating a shortened protein (ex. TGT --> TGA is Cys --> STOP; can cause diseases as serious as Cystic Fibrosis)
- SILENT- have no effects (i.e. no change) in amino acids of a protein (ex. GUU --> GUC is Valine; no changes just different base letters but coding for the same amino acid, common in Protein Synthesis)
- Frameshift: Occurs when bases are inserted or deleted from DNA sequence, shift in reading the frames of the codons which are differed as a result
- ADDITION- the addition of an extra amino acid or more in the DNA sequence to create altered amino acid sequence and possibly non-functional proteins (ex. Huntington's disease caused by insertion of duplicates of triplet nucleotides)
- DELETION- making the sequence shorter, missing one or more bases leading to completely different codons and a.a.'s and possibly a non-functional protein (ex. Can cause many diseases/disorders including infertility for males)
Here are good videso discussing mutations...
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