BIO206H5 Lecture Notes - Prokaryotic Small Ribosomal Subunit, Frameshift Mutation, 16S Ribosomal Rna

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olivealligator288

4 Jun 2019

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UTM

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Biology

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BIO206H5

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Translation Worksheet

Dayana Torres

Student Number: 1003931481

1. The amino acid codon(s) that, if altered, would most likely lead to premature termination of translation would be amino

acids that are similar to the stop codons (UAA, UAG, and UGA). This is because if an amino acid is altered so that it

becomes a stop codon, that would result in the termination of translation at a position that was originally supposed to be

coding for a particular region of the protein. These altered stop codons would not be located in regions that were supposed

to be the end of the protein, and due to their premature appearance, they would result in premature termination of

translation.

2a. Possible consequences of this change are:

- May result in an advantageous or disadvantageous change in the protein

- May result in an inviable protein (the new combination of amino acids don’t create a sustainable protein)

- Altered gene expression of the protein (when and where the protein is created or expressed)

2b. You could compare a segment of the tRNA gene for tyrosine without the mutation in the anticodon sequence and

compare it to the sequence whose tyrosine tRNA gens were mutated. By comparing the two, you could search for a

location on the mutated sequence that are different than the non-mutated sequence, thus determining which tRNA-Tyr

anticodon was altered.

3. The effect of truncating the 3’ end of the 16s rRNA of a prokaryote would be that the rRNA molecule wouldn’t be able

to base pair with the Shine-Dalgarno sequence (AGGAGGU). As a result of this, the mRNA wouldn’t be able to align

itself properly on the 30S ribosomal subunit, resulting in an inability to identify the start site for translation. If the start

point for translation cannot be determined, then it’s not possible for the correct amino acid sequence to be synthesized

from the mRNA template.

4. GTP plays a role in protein synthesis during:

- the matching of anticodon to tRNA; when aminoacyl-tRNA positions the anticodon in the A site, it’s released as GTP is

hydrolyzed to GDP and the ribosome changes shape

- moving the ribosome along the mRNA using the hydrolysis of GTP

5. Yes, RNA does have catalytic activity. Catalytic RNA (a ribozyme) is an RNA molecule that has the capacity to cleave

other molecules as well as itself in the absence of enzymatic proteins. An example of an RNA molecule with catalytic

active sites on it is RNA polymerase.

6. An activation reaction is reaction catalyzed by specific aminoacyl t RNA synthetases which is also called the activating

enzyme. The attachment of amino acid to a particular tRNA establishes the genetic code. Splice site mutations is genetic

code mutation that insert or delete a number of nucleotides. Frameshift mutations change the entire codon sequence. It can

be concluded that the mutation with the severest consequences is the frameshift mutation (either frameshift insertion or

frameshift deletion) therefore the answer is b.

7. Similarities between prokaryotic and eukaryotic translation are:

- Initiation factors are required for the start codon (AUG) to align correctly on the ribosomal subunit

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Related Questions

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

Attempt this question only if you can give complete explanation to your choice. This is biology/genetics question

If an mRNA contains a protein-Ââcoding sequence that has 33 codons (including the start and stop codons), how many amino acids will be in the protein that is produced from translation of that mRNA?

a. 99

b. 32

c. 33

d. 11

e. 0

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.