BSCI-1510 Lecture Notes - Lecture 35: Alanine, Peptide, Ribosomal Rna

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indigoraccoon343

4 Apr 2016

School

Vanderbilt University

Department

Biological Sciences

Course

BSCI-1510

Professor

Singleton Charles

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Document Summary

Stop codon is defined by defining the start codon and going 3 by 3 it has to be in the proper reading frame. If it"s not in the reading frame, it is not a stop codon there;s information to say that aug is a start codon not always a start codon. methionine. Mutations and their effects on the coded protein. One of the things we already talked about. Frameshift addition of one or two or deletion of one or two shifting the reading frame with respect to the effect on the protein. This changes all the information (codons) downstream from the addition or deletion. The addition or deletion can be any non-multiple of three deleting three, removing the information from one amino acid but without changing the whole sequence. The second of effects is referred to as a missense mutations this is caused by point mutation in the dna.

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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.

mauvetrout554

Mutations that introduce stop codons cause a number of geneticdiseases. For example, from 2% to 5% of the people who have cysticfibrosis possess a mutation that causes a premature stop codon inthe gene encoding the cystic fibrosis transmembrane conductanceregulator (CFTR). This premature stop codon produces a truncatedform of CFTR that is nonfunctional and results in the symptoms ofcystic fibrosis. One possible way to treat people with geneticdiseases caused by these types of mutations is to trick theribosome into reading through the stop codon, inserting an aminoacid into its place. Although the protein produced may have onealtered amino acid, it is more likely to be at least partlyfunctional than is the truncated protein produced when the ribosomestalls at the stop codon. Indeed, geneticists have conductedclinical trials on people with cystic fibrosis with the use of adrug called PTC124, which interferes with the ribosome's ability tocorrectly read stop codons (C. Ainsworth, 2005, Nature438:726â728). On the basis of what you know about the mechanism ofnonsense-mediated mRNA decay (NMD), would you expect NMD to be aproblem with this type of treatment?

	Yes, NMD would be a problem, as it requires ribosome torecognize a specific stop codon.
	Yes, NMD would be a problem because even although the ribosomewould read through the stop codon, premature degradation of themRNA would take place.
	None of the above is true.
	No, NMD would not be a problem because the ribosome would readthrough the mutated stop codon, removing exon-junction proteinsthat would normally signal premature degradation of mRNA.
	No, NMD would not be a problem because it only occurs inprokaryotes.

coralsheep993

Fill in the blank. Elongation during translation does NOT involve ____________.

Question 16 options:

	the translation of codons according to the genetic code
	the formation of bonds catalyzed by the ribosome
	complementary base pairing between RNA molecules
	amino acids being linked together in a polypeptide
	reading the DNA template 3' to 5'

For a given gene, what establishes the reading frame for translation?

Question 17 options:

	the location of the enhancer relative to the gene
	the first three nucleotides at the 5' end of the mRNA
	the first three nucleotides at the 3' end of the mRNA
	the start codon in the mRNA
	the location of the promoter relative to the gene

Which of the following is the LEAST likely direct consequence of a substitution mutation?

Question 18 options:

	changing the length of a protein coded for by a gene
	changing one amino acid in a protein
	creating a stop codon
	eliminating a start codon
	changing the length of the DNA molecule containing a gene

Suppose that the pre-mRNA transcript from a eukaryotic gene is 30,000 nucleotides long, and the gene codes for a sequence of 300 amino acids. What is the best explanation for the relationship between these numbers?

Question 19 options:

	only the first 900 nucleotides of the pre-mRNA transcript are translated
	it takes 100 nucleotides to specify a single amino acid
	300 of the nucleotides in the transcript are important, and the rest are "junk"
	only the last 900 nucleotides of the pre-mRNA transcript are translated
	large portions of pre-mRNA transcripts are cut out during RNA processing

Suppose an individual is born into a population with a novel mutation. Is the new mutation an evolutionary change, and why?

Question 20 options:

	no, because it is not a big enough change to count
	yes, because new mutations are always adaptive
	yes, because the appearance of a new genetic variant is a genetic change in a population
	no, because not enough individuals have the mutation for it to matter
	no, because most mutations are not adaptive

BSCI-1510 Lecture Notes - Lecture 35: Alanine, Peptide, Ribosomal Rna

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