Question

3. (1.8 points) The normal CFTR gene contains these six codons near the middle of the transcript: AUU UCU VUA GCA AGA GCU... Al The corresponding amino acids in the normal CFTR protein are: (Use either the one-or three-letter amino acid codes A naint mutation changes the last nucleotide from U to C. At the DNA level, this is a transition transversion c) At the protein level, this is a (silent / missense / nonsense/frameshift ) mutation. D) Instead of a point mutation, assume that a DNA polymerase error deletes a base during replication. The new sequence is ...AUU CUU UAG CAA GAG CU... The corresponding amino acids in the mutated CFTR protein are: E) At the protein level, this is a (silent/missense/ nonsense/frameshift ) mutation. (1.2 point) In a prokaryotic gene, a mutation occurs in the TATAAT box that changes it to TAGAAT. A) This mutation is neither silent, missense, nonsense, or frameshift. Why not? B) It is likely that this mutation will have an effect on transcription. Why? (1.8 point) In a eukaryotic gene, a mutation occurs at splice donor site, changing it from GT to CT. A) This mutation is neither silent, missense, nonsense, or frameshift. Why not? -) It is NOT likely that this mutation will have an effect on transcription. Why not? It is likely that this mutation will have an effect on the protein translated from the mRNA. Why?

Answer 1

1) given sequence is

AUU UCU UUA GCA AGA GCU

a) the amino acid sequence is

Ile-Ser-Leu-Ala-Arg-Ala

the point mutation changes to

AUU UCU UUA GCA AGA GCC

the amino acid sequence is Ile-Ser-Leu-Ala-Arg-Ala

here there is no change in the amino acid sequence so this is an example of silent mutation, both GCU and GCC codes for same amino acid. here U is changed to C,

transition mutations are mutations which changes one purine to another purine or a pyrimidine is changed to another pyrimidine and transversion mutations are mutations which change one pyrimidine to a purine, cytosine and uracil are pyrimidines so this is a transition mutation

b) Transition mutation

c) silent mutation

d) the sequence after the deletion of the last nucleotide is

AUU UCU UUA GCA AGA GC

the amino acid sequence is Ile-Ser-Leu-Ala-Arg

e) here one nucleotide is deleted so this is an example of frameshift mutation, the reading frame downstream to the mutation changes due to the deletion or addition of one or two nucleotides.