NEET Biology: Genetics questions with solutions

Q1. In male grasshoppers and moths, there are two pairs of autosomes and

1. \( x \) only
2. x and
3. Y only
4. None of the above

Answer: x and

In male grasshoppers and moths, the sex-determination system is XO: males have two pairs of autosomes plus a single X chromosome. There is no Y chromosome in this system, so the missing sex chromosome is represented by the X alone.

Q2. Which is not an example of cytoplasmic inheritance?

1. Female sterility in maize
2. Sigma particle inheritance
3. Kappa particle inheritance
4. Plastid inheritance

Answer: Female sterility in maize

Female sterility in maize is not a classic example of cytoplasmic inheritance; it is generally associated with nuclear-cytoplasmic interactions rather than direct inheritance through cytoplasm alone. Sigma particles, kappa particles, and plastids are all transmitted through the cytoplasm.

Q3. In the lac operon, the structural genes are switched off when repressor binds to the

1. Operator
2. Promoter
3. Regulator
4. Inducer E. Allolactose

Answer: Operator

In the lac operon, the repressor shuts off transcription by binding the operator, a DNA segment that controls access to the structural genes. This blocks RNA polymerase from transcribing the operon.

Q4. Male \( X X \) and female \( X Y \) sometime such conditions occur due to

1. Deletion
2. Transfer of segments in \( x \) and \( Y \) chromosomes
3. Aneuploidy
4. Hormonal imbalance

Answer: Aneuploidy

A male with XX chromosomes or a female with XY chromosomes usually results from an abnormal number or combination of sex chromosomes, which is a form of aneuploidy. Deletions, segment transfers, or hormonal imbalance may affect sex development, but they do not by themselves explain the chromosomal sex reversal described here.