Question

QUESTION 6

1. The lac repressor in bacteria _______, and when lactose is present, the lac genes ______.

   		Activates transcription of lactose-metabolism genes; are transcribed
   		Activates transcription of lactose-metabolism genes; are NOT transcribed
   		Inhibits transcription of lactose-metabolism genes; are transcribed
   		Inhibits transcription of lactose-metabolism genes; are NOT transcribed

0.5 points   

QUESTION 7

1. There are ____ different nucleotide bases in DNA and RNA and ___ different amino acids.

   		3; 61
   		3; 21
   		4; 20
   		4; 61

0.5 points   

QUESTION 8

1. Which of the following aspects of transcription is true for bacteria but not Eukaryotes?

   		A 7-methyl guanosine cap at the 5' end of mRNA increases stability.
   		Transcription and translation may occur simultaneously.
   		Only bacteria have mRNAs
   		RNA splicing.

0.5 points   

QUESTION 9

1. Imagine that you are on a camping trip with your friends in the Adirondacks. The unusually cold, wet spring has led to an abundance of fungi, and you discover a species of fungus previously unknown to science. When you take a specimen back to the lab, you find that it secretes copious amounts of a peptide that inhibits 5’ capping of mRNA. One of your friends suggests using this new peptide as an antibiotic with which to treat bacterial infections.Why is this a bad idea?

   		Bacterial mRNAs are not capped.
   		The enzyme that caps mRNA in bacteria is different from the one in eukaryotes.
   		The antibiotic would have the side effect of preventing capping of the patient’s mRNA.
   		Peptides are not useful antibiotics.
   		Both 1st and 3rd answers above

0.5 points   

QUESTION 10

1. Which of the following has activity that is most similar to RNA Polymerase?

   		Primase
   		Helicase
   		Exonuclease
   		DNA Polymerase

Answer 1

And 6- inhibits transcription of lactose- metabolism genes; are transcribed.

Repressor is meant for blocking the operator gene so that the structural genes are unable to form mRNA. it has two sites one for attaching to operator gene and second for binding to inducer. After coming in contact with inducer the repressor undergoes conformational change in such a way that it is unable to combine with operator, here inducer for Lac operon is lactose. Thus, the lac- repressor in bacteria inhibits transcription of lactose-metabolism genes and when lactose is present, the lac genes are transcribed.

And 7- 4, 20. There are 4 different nucleotide bases in DNA and RNA that is adenine, guanine, cytosine, and thymine (in DNA) or uracil (in RNA) and 20 different amino acids.

And 8- transcription and translation may occur simultaneously.

RNA splicing, a 7 methyl guanosine cap at the 5' end of mRNA to increase its stability are features in eukaryotes during post transcriptional modifications which takes place to transport mRNA from nucleus to cytosol, since translation takes place in cytosol in eukaryotes.

In bacteria, no such compartments are present therefore translation starts before transcription is complete as both processes are taking place in cytosol.

Ans 9- Both 1st and 3rd answers above;

Bacterial mRNA's are not capped as post transcriptional modifications are not required therefore peptide inhibiting 5' capping is of no use in bacterial infections. Further, this antibiotic can complicate the situation by preventing capping of patient's mRNA, as patient is eukaryote and as already discussed capping do takes place in eukaryotic mRNA to make it stable thus, the antibiotic would have the side effect of preventing capping of patient's mRNA.

Ans 10- helicase. In contrast to DNA polymerase, RNA polymerase has helicase activity, therefore no separate enzyme is needed to unwind DNA.

Thank you

Hope it helps

Feel free to ask further doubts in comment section below.