Biology 1002B Lecture Notes - Lecture 18: Frameshift Mutation, Stop Codon, Nonsense Mutation

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19 Oct 2018

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If it changes and makes it now a stop codon, this is called a nonsense mutation: frameshift mutation. Insertion or deletion of a single base pair, this can have devastating effects. It is hard to predi(cid:272)t, (cid:449)e do(cid:374)"t k(cid:374)o(cid:449) (cid:449)hat the effe(cid:272)t (cid:449)ill (cid:271)e u(cid:374)less (cid:449)e k(cid:374)o(cid:449) so(cid:373)ethi(cid:374)g a(cid:271)out the fra(cid:373)e that"s (cid:271)ei(cid:374)g (cid:272)ha(cid:374)ged. The nuclei around the surface (smarties) need to figure out where they are so they can express different genes. How could you discover the genes involved in development: look for natural mutants that are not properly developing, try to see if there is something different about their genome and identify a gene that changed. If the answer is a lot, then i know i am near the head. The phenotype of a maternal effect gene is not determined by the genotype of the organism, but rather by that of its mother.

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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.

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PART C IS THE PART I NEED HELP WITH PLEASE

Below is a partial mRNA sequence. Use it to answer the following questions.

5' - GCCGAUCGAACU - 3'

What is the correct reading frame for this mRNA?

5' - G | CCG | AUC | GAA | CU - 3'

If a single base-pair deletion occurred in the part of the gene that corresponds to the mRNA above and the resulting partial amino acid sequence was (N-term-...P-M-N...-C-term), which new partial mRNA sequence would be consistent with this change?

5' - G | CCG | AUG | AAC | U - 3'

Part C

The amino acids in the original partial sequence (N-term-...P-I-E...-C-term) have little to no impact on protein structure and function. However the amino acid sequence near the C-terminal end of the protein is required for normal function. Any amino acid changes in this region of the protein will result in a nonfunctional protein.

Given this information, which reversion mutation in the gene would restore the normal function of the protein?

Select all that apply.

Insertion of 2 base-pairs in the region of the proline codon

Deletion of 5 base-pairs in the region of the proline codon

Deletion of 2 base-pairs in the region of the proline codon

Deletion of 1 base-pair in the region of the proline codon

Insertion of 1 base-pair in the region of the proline codon

Insertion of 4 base-pairs in the region of the proline codon

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1. An occurrence of a gene made larger by trinucleotide repeats is:

Allelic expansion

Nucleotide expansion

Translocation mutation

Transformation

2. a chemical that can damage and/or change DNA is called a/an:

Allele

Endonuclease

Vector

Mutagen

3. An occurrence when a section of a chromosome relocates itself to an entirely different (non-homologous) chromosome is called a/an:

Inversion mutation

Translocation mutation

Transformation mutation

Duplication mutation

4. The tandem repeat in the sequence GGGAAGGGAAGGGAAGGGAAGGGAAG is:

GGA

GGGAA

GGAAG

GGAAGGG

A disease characterized by abnormally shaped hemoglobin is called:

Cystic Fibrosis

Sickle Cell Anemia

Marfan Syndrome

Leukemia

5. A point mutation that causes a substitution of a stop codon with an amino acid and leads to the formation of a longer protein is a:

Nonsense mutation

Missense mutation

Sense mutation

Frameshift mutation

6. Addition or deletion of nucleotides in a DNA sequence is known as a:

Nonsense mutation

Missense mutation

Sense mutation

Frameshift mutation

7. The least severe type of chromosomal mutation is:

Point

Frameshift

Inversion

Translocation

8. Chemicals inserting themselves into DNA can cause a:

Missense mutation

Nonsense mutation

Sense mutation

Frameshift mutation

9. A genetic condition caused by allelic expansion is:

Familial hypercholesterolemia

Fragile X syndrome

Alkaptonuria

Galactosemia

10. Which of the following is most likely the original DNA strand if the mutated DNA strand is ATAGUUGATGUA ?

ATAGAAGATGAA

ATAGCCGATGCA

ATAGGGGATGGA

ATAGTTGATGTA

11. An unbalanced chromosomal mutation would include a/an:

duplication (insertion)

inversion

translocation

denaturation

12. Many translocation mutations are found to be involved with:

cancers

sickle cell anemia

Huntington disease

cystic fibrosis

13. A common repeat throughout the human genome that is approximately 300 bases in length is called a/an:

EcoRI repeat

Hind repeat

Exo repeat

Alu repeat

14. A balanced chromosomal mutation includes:

imprintation

denaturation

inversion

deletion

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Biology 1002B Lecture Notes - Lecture 18: Frameshift Mutation, Stop Codon, Nonsense Mutation

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