BI111 Lecture Notes - Lecture 2: Zygosity, Missense Mutation, Nonsense Mutation

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12 Jan 2016
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Genotype describes what is on the inside
Phenotype describes what is on the outside
Introns removed from pre-mRNA before translation
Translation:
Takes “letters” and reads them in a section of 3 (codons) make
up the language of life
Is a constant
Each codon codes for an amino acid
Genetic code was established very early in the evolution of life
and has remained unchanged.
There is speci'city and redundancy within the codons
Dna strand is transcribed to make the mRNA strand, process and
used to build a polypeptide bond- and together a protein is built.
Mutations:
Missense mutation:
300-400
alters the amino acids, which had the potential to change the
whole protein.
Nonsense mutation:
Stops prematurely
Useless because it is not complete
Silent Mutations
Codon changed to another for the same amino acid
Frame shift mutation:
Reads every 3 letters
Add or take away a letter the codons will be di/erent because
the altered reading of the codons.
Changes entire sequence
Mutations aecting Phenotypes
Single mutation can have a big impact on an individual
phenotype
Many alleles, which leads to variation in phenotypes
Alleles
Homologues chromosomes (unreplicated) same chromosomes
same size, one from mom, one from dad
2 identical copies- both donated AA or aa are homozygous
1 A, 1a, heterozygous, mismatch between the two alleles at that
loci
Pleiotropic eects of phenotype
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