Download Practice Questions (Part 2) KEY

Practice Questions (Part 2) KEY
APPLY THE CONCEPT – Mutations are changes in DNA
From the question introduction paragraph, you should understand that it is predicted that Meat Extract
(that comes from meats preserved with nitrites) will cause mutations, while ascorbate (Vitamin C)
may or may not decrease (or counteract) these mutations. The scientists want to see the affect of
ascorbate on the rate of mutations caused by meats preserved with nitrites.
1. The experiment with no extract and no ascorbate acts as the control. This is what will be used as
the baseline for comparison. This experiment shows that there is a baseline rate of 2 mutations
(x10^-5).
2. The experiments with increasing amount of extract and no ascorbate shows that as meat extract
increases, the rate of mutation also increases in comparison to the baseline rate of 2.
3. When ascorbate is added to increasing amounts of extract, the rate of mutation returns to the
baseline rate of 2. Therefore, it can be concluded that ascorbate decreases the rate of mutation
caused by meats preserved with nitrites.
4. The mutated strain had a T instead of a C at position 2. This is a point mutation, probably caused
by DNA polymerase.
APPLY THE CONCEPT – The genetic code in RNA is translated into the amino acid sequences
of proteins
1. Because RNA is synthesized in the 5’3’ direction, the DNA is read in the 3’5’ direction.
Therefore, the DNA strand that is transcribed is the bottom strand.
2. RNA:
polypeptide:
5’
AUG UUU UCG ACG UGC GAU UGA
met phe ser
thr
cys
asp stop
3’
3. The codon becomes UCU which still codes for serine, therefore there is no change to the protein.
4. The codon probably became UGA which codes for stop. (In the DNA, the G at position 15 is
changed to T, which would result in the codon of UGA in the RNA).
Multiple Choice (on the back)
1.
2.
3.
4.
5.
6.
C
E
E
b – gene that codes for repressor protein, c – promoter, d – operator, e – repressor protein
C
C