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Questions in Mutations
Page 5 out of 6 Pages
- Insertion mutations result in a null phenotype and most are caused by Transposons. What are transposons are. What is their actual role with regards to mutations? (5365 views)
- While re-listening to the lecture and looking over my notes, I realized I was somewhat confused by a 3
base deletion. In class we assumed that the 3 bases that were deleted were all part of the same codon
and thus only one protein would be deleted. Is it not possible for those 3 bases to actually be part of 2
separate codons? Because that would mean that in effect two amino acids are deleted and a new one is
formed. And could the same idea be applied to a 3 base insertion?
(4910 views)
- In my notes it first says "DNA replication is the most reliable" but then on the next page it says "Most
mutations occur during DNA replication" (These are quotes directly from the ppt. notes, not my
handwritten notes) ... the weekly review question (Question 3 from WR 7) was a T/F statement:" More
mistakes are made during transcription than DNA replication. " I said false because I figured even if DNA
replication makes fewer mistakes, it has the opportunity to make a larger number of mistakes because as the notes say "that's when huge amounts of DNA are synthesized"; therefore the quantity of mistakes made would be greater from replication. The statement in the weekly review question was true, however, so I am confused. Could you please explain the flaw in my thinking and also clarify what seems to be a contradiction in the lecture notes?
(5365 views)
- In one of our homework questions, I had the following:
The figure below represents a portion of a protein-coding gene. Only one strand is shown, and the strand shown is the template strand. If each codon of the resulting mRNA is read in-frame from the appropriate end of the transcript, which one of the following most accurately represents the nature of the mutation illustrated in the second template strand?
5'…ATAAGCCGTATAGCGGGA…3' wt
to
5'…ATAGGCCGTATAGCGGGA…3' mutant
Incorrect: Deletion
Incorrect: Missense mutation
Incorrect: Nonsense mutation
Incorrect: Insertion
Correct: Point mutation
I put missense mutation, which I thought was the answer because the amino acid specified does indeed change, and it's not a stop codon. I thought it could be point mutation as well, but isn't missense MORE SPECIFIC than point mutation because a missense is a type of base substitution mutation which in turn is a type of point mutation?
And another related question, frameshift mutations are also point mutations, correct?
Could you clarify these two issues? (14406 views)
- In one of my notes for cystic fibrosis, it says "causes Cl- to accumulate in cells, causing water to be taken into cells." What exactly does Cl- do?(5138 views)
- Why is this statement false: "Deletions that occur in the coding region of a gene typically result in a protein product with slightly reduced function?"(4977 views)
- I know that transposons are the "jumping genes" which are responsible for most chromosome level mutations, but what is it that is causing them to jump?(5169 views)
- For the question "Which one of the following players in the E. coli DNA mismatch repair system possesses the ability to hydrolyze a phosphodiester linkage in a molecule of deoxyribonucleic acid?", why is the answer DNA Pol III, and NOT DNA Pol I? Don't they both hydrolyze phosphodiester linkages in the 3'-5' direction, but DNA Pol I, can also do it 5'-3'?(6237 views)
- Is excision repair not the same thing as the mismatch repair? If not, how do they differ?(4004 views)
- I have a question involving mismatch repair: When Professor Mehrtens mentioned that the methylase enzyme comes and scans for a particular sequence (GATC), adding a methyl group to the A, is this referring to the newly synthesized strand or the parent strand?
I know that the parent strand is methylated, whereas the daughter strand isn't. What exactly is methylated - is it only the A's in E.coli and G/C's in humans? or is the whole parent strand methylated? I wrote in my notes: "If the parent strand is methylated and the newly synthesized strand is not, we need to fix the non-methalyated stand." Could you please clear that up for me? (4182 views)