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

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School
Western University
Department
Biology
Course
Biology 1002B
Professor
Tom Haffie Denis Maxwell

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Class 18: Development and Death
Tips
- Use figures that compile transcriptional regulation, posttranslational regulation,
translational regulation, and posttranslational regulation
Missense mutation - change in base pair (snp) that changes the amino sequence but THIS one
does not
• Suffer a snp in DNA code that has no affect, changes an amino sequence into the same
amino acid
• Changes the codon
Nonsense mutation - change by a snp and changes the amino acid to a stop codon
Frameshift mutation - insertion or deletion in the amino acid
• Shifts the reading frame of the sequence
• Codons are read by 3 pairs, affects the whole sequence downstream
Mental floss – if a single pair insertion into the DNA coding for the first exon of the above
mRNA, how does that change the length of the sequence?
• The protein is most likely to be too short, too long, unchanged, or undetermined
• Can be too short if it codes for a stop codon and the sequence becomes too short
• Can be too long if a base is inserted and the coding region goes passed the 3' UTR
• Difficult to predict, so really have no idea
• Can e unhanged if…
• What if the sequence suffers mutations?
Drosophila: why is it a good model system?
• Egg gets fertilized to get a nucleus and divides, but the cell does not
• Multi-nucleic egg
• Cell membranes grow around them
• Gastrula is highly segmented
• Process of segmentation
• Simple organism, you can find this anywhere
The genome of flies need to grow flies and worms
• Drives the construction of flies and worms
How could you discover the genes involved in development?
• Look for natural mutants
• Feed chemicals to make mutants and look for mutations
• Selectively delete genes
• Knockout genes
• Compare transcript abundance
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Related Questions

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 5’-AUGCAUACAUUGGAGUGA-3’
mutant 5’-AUGCAUACAGAGUGA-3’
b) wild-type 5’-AUGCAUACAUUGGAGUGA-3’
mutant 5’-AUGCAUACGUUGGAGUGA-3’
c) wild-type 5’-AUGCAUACAUUGGAGUGA-3’
mutant 5’-AUGCAUACAUCUGGAGUGA-3’
d) wild-type 5’-AUGCAUACAUUGGAGUGA-3’
mutant 5’-AUGCAUGUGACAUUGGAGUGA-3’

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?

5’-ATGCTAGCCTATCGTAAC-3’

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.

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