Biochemistry 2280A Lecture : Mutations

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orchidotter238

29 Dec 2011

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We got rna sequence wild type first is mutation where we put gcc as ggc single base mutation. What does this do for protein results in single amino acid change from alanine to glycine. Alanine and glycine are functionally similar . not identical but similar good chance that glycine might allow for functional protein. If alanine were converted to arganine or something else theres higher chance that protein is dysfunctional. May affect protein function but it may not. Frame shift mutation (addition of one, two, or three bases). It changes the encoded protein completely from the pt of the mutation to the c terminus. Everything from the red a is going to change (bade mutations huge changes) When it is a multiple of 3 bases. Insertino or deletion of a base resutls in a change in reading frame of the protein from pt of the mutation onward . Frame of reading si changed, thus it will change sequence.

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The effect of base-pair substitution mutations on protein function varies widely from no detectable effect to the complete loss of protein function (null allele).

Part A Why do the functional consequences of base-pair substitution vary so widely? Select the four correct answers.

1. Nucleotide substitutions might not cause changes in the amino acid sequence of the protein.

2. The reading frame of the gene could be affected by base-pair substitution mutations, which almost always leads to lack of function.

3. Nucleotide substitutions in exons always lead to changes of amino acids in the protein.

4. The reading frame of the gene could be affected by base-pair substitution mutations, which rarely leads to lack of function.

5. Missense mutations create amino acid substitutions, which might affect protein functionality.

6. Mutations that occur in the intron sequences generally do not affect protein functionality.

bluelion973

Part B

Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?

a) It could cause a frameshift nonsense or frameshift missense mutation because it would change the reading frame of the codon triplet.

b) It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.

c) It could cause a nonsense mutation because the sequence would no longer be the same, so the protein would be shorter and non-functional.

d) It could cause a silent mutation because A and T are complementary to each other so it is not really a substitution mutation.

Part C

Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?

a) A substitution missense mutation causes the protein to be shorter and thus non-functional.

b) A frameshift missense will cause the codons to be out of order, but a substitution missense does not change the order of the codons.

c) A frameshift missense mutation will cause an early Stop codon, but a substitution missense might be silent.

d) A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.

Part D

Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?

a) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAGAGUGA-3â

b) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACGUUGGAGUGA-3â

c) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAUCUGGAGUGA-3â

d) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUGUGACAUUGGAGUGA-3â

Part F

Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein?

5â-ATGCTAGCCTATCGTAAC-3â

a) The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.

b) The entire amino acid sequence would be altered due to the frameshift.

c) All of the amino acids after the deletion would be altered due to the frameshift.

d) All of the amino acids up to the deletion would be altered due to the frameshift.

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Biochemistry 2280A Lecture : Mutations

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