Question

QUESTION 36

1. Consider two theoretical transposable elements in yeast, A and B. Each contains an intron and each transposed to a new location in the yeast genome. Suppose you then examine the transposons for the presence of the intron. In the new locations, you find that A has no intron but B does. From these facts, what can you conclude about the mechanisms of transposition for the two transposable elements?

   	A.	A probably doesn't create a duplication of the host genome target sequence.
   	B.	B probably makes a reverse transcriptase.
   	C.	B probably makes a transposase.
   	D.	B probably uses RNA as an intermediate in the transposition event.
   	E.	A probably has inverted repeats at each end of the element.

QUESTION 38

1. _____ mutations produce new activities and are usually dominant.

   	A.	Lethal
   	B.	Spontaneous
   	C.	Gain-of-function
   	D.	Induced
   	E.	Forward

QUESTION 44

1. A lac operon of genotype lacI⁺ lacP⁺ lacO⁺ lacZ⁺ lacY^– will produce β-galactosidase but not permease when:

   	A.	in the presence or absence of lactose.
   	B.	lactose is present.
   	C.	glucose is present.
   	D.	lactose is absent.
   	E.	glucose and lactose are both present.

Answer 1

36. Correct answer: a. A probably dosen't create a duplication of the host genome target sequence.

38. Correct answer: c. Gain of function. Gain of function mutation is a type of mutation in which the altered gene product possesses a new molecular function or a new pattern of gene expression. Most of the time random genetic changes are introdued due to mutations which mostly result in loss of function of that gene. Gain of function mutations are almost always dominant or semidominant. In homozygous condition mutation in one gene won't affect the function of gene as there is another normal copy of that gene. In heterozygous condition, gain of function mutation will act like a dominant allele and produce some kind of new phenotype.

44. Correct answer: b. Lactose is present. A lac operon of genotype lacI+ lacP+ lacO+ lacZ+ lacY– will produce β-galactosidase but not permease in presence of lactose. Lactose will act as inducer and will bind repressor protein making it inactive. Thus transcription of lac operon will take place and beta-galactosidase will be produced since the given genotype of lac operon has functional Lac Z gene. Permease will not be produced because the genotype has mutated Lac Y gene which is responsible for production of permease. In presence of glucose lac operon transcription will be inhibited.