Question

28

28. Genes found in segments of chromosome called heterochromatin would likely be expressed at high levels. expressed at low levels, or not at all. deleted before replication. maternally inherited only. none of these

29

30

31

32

33

Answer 1

Question 28 :-

The right option is option (b) expressed at low levels or not at all

Explanation :- Heterochromatin is the region of the DNA which is highly coiled and condensed. This means that the DNA is not readily available for RNA polymerase to transcribe it. Thus it is expressed much lower. The opposite of heterochromatin is Euchromatin in which transcription rate is high.

Question 29 :-

The right option is option (a) 3' to 5' along the template strand.

Explanation :-

Firstly, RNA polymerase uses Template strand hence the name template strand. So it will move on it. Now the new RNA which is created, is in 5' to 3' direction and since DNA strands are complimentary, it mean the orientation of the template strand will be opposite. So if new stand is synthesized in 5' to 3' direction, that means DNA template Orienation will be 3' to 5'

Question 30 :-

The right option is option (b) To the right of the template strand.

Explanation :-

Promoter is present before the start codon of DNA. And since the start point is 3" end, then it will be before that. That is right to the 3' end. Hence the promoter will be to the right of 3' end of template strand.

Question 31:-

The right option is option (D) can allow the production of different sizes of protein and function from a single pre-mRNA

Explanation:-

In splicing, introns are removed while exons are kept in a mRNA. While in alternate splicing, some exons are removed too. Now, exons are the part of mRNA which codes for protein. Suppose a mRNA have 5 exons namely :- A B C D E. Now different combinations can be made like A B C D or A C D E or A B D and so on. So using alternative splicing, cells can use one mRNA to create different types of mature mRNA which will code for different proteins with different size and function.

Question 32:-

The right option is option (c) Any mutation in the sequence is highly selected against

Explanation :-

Conserved sequence means that it is almost universal and found in a wide variety of organisms across Genera, phylum and kingdom. But it doesn't mean that it can not mutate because the fact is that mutation is random and any sequence of DNA is equally probable to be mutated. But, cells can prevent mutation not by stopping mutation but by selecting against it. It means if a cell have a mutation in one of the important, conserved gene, the resulting cell or organism will not survive and die. Thus, it will not pass on the mutation to its possible progeny. Hence, the selection opposes accumulation of mutation in conserved genes.

Question 33 :-

The right option is option (B) Taq polymerase.

Explanation :-

In PCR, which uses a thermocycler and the temperature is raised to as high as 94° Celsius, the proteins in the solution can be degraded by heat. Because proteins, especially enzymes are very sensitive to temperature changes. Actually, earlier scientists has to add polymerase enzyme after every cycle. But now we uses polymerase enzymes from those bacteria which survive in high temperature like in Hot water spring because their proteins are resistant to high temperature.

Taq polymerase is extracted from a bacteria called Thermus aquaticus and it is found in Hot water springs at high temperatures.