Question

Genetics: Upcoming exam, want to be prepared knowing the following questions. Make sure to answer with one letter only. THANK YOU FOR YOUR HELP.

1. Recombination in individuals heterozygous for a ______ can produce chromosome containing two centromeres.

a. inversion

b. translocation

c. duplication

d. deletion

e. RFLP

2. An E.coli strain possesses the following phenotype F(P+)/I^-P^cO^+Z^+Y^+ where I^- is a mutation that eliminates production of the repressor and P^c eliminates the ability of the polymerase to bind the promoter. The structural genes on the chromosome

a. will be transcribed in the presence and absence of lactose

b. will be transcribed only if lactose is present

c. will not be transcribed under any conditions

3. An E.coli strain possesses the following phenotype F(O^c)/ I^+P^+O^+Z^+Y^+ where O^c is a mutation in the operator that prevents repressor binding.

a. will be transcribed in the presence and absence of lactose

b. will be transcribed only if lactose is present

c. will not be transcribed under any conditions

Answer 1

1. Correct answer:- (c) duplication
Explanation:- duplication (doubling of the chromosome) can produce two centromere.
- One chromosome have only one centromere.

2. Correct answer:- (c)will not be transcribed under any conditions.

3. Correct answer:- (a) will be transcribed in the presence and absence of lactose.
Explanation:- mutations in the operator, the binding site for repressor, lead to lower affinity for the repressor and hence less binding.
-Thus these mutations allow continued transcription (and thus expression) of the lac operon even in the absence of inducer, this is referred to constitutive expression.