GPB MCQ Quiz 168 for ICAR JRF/SRF/ARS Exam Preparation

Genes those have little or no effect of their own but increase or decrease the expression of other major genes are called

A) Oligogenes

B) Modifying genes

C) Poly genes

D) None of the above

Explanation: Modifying genes alter the expression of major genes but have little or no independent effect themselves.

The ability of gene to express itself in an individual that carries it is called

A) Penetrance

B) Incomplete penetrance

C) Threshold character

D) Expressivity

Explanation: Penetrance refers to the proportion of individuals with a particular genotype that actually express the associated phenotype.

An organism may be of a genotype aa or AA but may not express the phenotype associated with its genotype due to modifying effect of the environment or due to modifiers – such genes are supposed to have

A) Penetrance

B) Incomplete penetrance

C) Complete penetrance

D) Expressivity

Explanation: Incomplete penetrance occurs when some individuals with a specific genotype do not express the expected phenotype due to environmental or genetic modifiers.

The gene which expresses itself in every individual that carries it is said to have

A) Penetrance

B) Complete penetrance

C) Incomplete penetrance

D) Expressivity

Explanation: Complete penetrance indicates that all individuals carrying the genotype express the associated phenotype.

The extent to which a given genotype is expressed phenotypically in an individual is

A) Penetrance

B) Incomplete penetrance

C) Complete penetrance

D) Expressivity

Explanation: Expressivity refers to the degree to which a genotype is phenotypically expressed in an individual.

The characters whose development depends upon a specific environment are referred to as

A) Penetrance

B) Expressivity

C) Threshold character

D) None of the above

Explanation: Threshold characters are traits that manifest only when environmental conditions reach a certain level.

The net effect on the trait depends upon the combined action of several genes, each of which has a small effect on the same trait. Such genes are called

A) Poly genes

B) Cumulative genes

C) Both

D) None of the above

Explanation: Polygenic traits result from the combined effect of several genes, each contributing a small additive effect.

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