Principles of Inheritance and Variation

NEET Biology · 167 questions · Page 15 of 17 · Click an option or "Show Solution" to reveal answer

Q141

After a mutation at a genetic locus, the character of an organism changes due to change in

A protein structure

B DNA replication

C protein synthesis pattern

D RNA transcription pattern

Correct Answer

Option A

Solution

(a) Mutation changes the DNA sequence → altered codon → altered amino acid → changed protein structure → changed phenotype.

Q142

One of the parents has a mutation in its mitochondria and is taken as the male parent. During F2 segregation, the mutation is found in

A one-third of progenies

B none of the progenies

C all progenies

D fifty percent of progenies

Correct Answer

Option B

Solution

(b) Mitochondria are maternally inherited; mutation in male parent is not transmitted to progeny.

Q143

A normal woman whose father was colour blind is married to a normal man. Percentage of colour blind sons is

A 75%

B 50%

C all normal

D all colour blind

Correct Answer

Option B

Solution

(b) Woman is carrier (X^c X); sons: 50% colour blind (X^c Y) and 50% normal (XY).

Q144

A man with a certain disease marries a normal woman. All daughters suffer from the disease but none of the sons are affected. Mode of inheritance is

A Sex-linked recessive

B X-linked dominant

C Autosomal dominant

D Sex-limited recessive

Correct Answer

Option B

Solution

(b) All daughters affected by father's disease = X-linked dominant (daughters get father's X).

Q145

A woman with 47 chromosomes due to three copies of chromosome 21 is characterized by

A superfemaleness

B triploidy

C Turner syndrome

D Down syndrome

Correct Answer

Option D

Solution

(d) Down syndrome: trisomy 21 (47 chromosomes).

Q146

Barr body in human female is formed by inactivation of

A paternal X-chromosome

B maternal X-chromosome

C both X-chromosomes

D either the paternal or maternal X-chromosome randomly

Correct Answer

Option D

Solution

(d) According to Lyon hypothesis, either X chromosome (paternal or maternal) is inactivated at random.

Q147

An individual exhibiting both male and female sexual characteristics is known as

A hermaphrodite

B intersex

C gynandromorph

D bisexual

Correct Answer

Option C

Solution

Q148

Drosophila flies with XXY genotype are females but in humans such individuals are abnormal males. This indicates that

A The Y chromosome has no role in sex determination

B In Drosophila, Y chromosome is essential for sex determination

C The Y chromosome is male determining in humans

D The Y chromosome is female determining in Drosophila

Correct Answer

Option C

Solution

(c) In humans, the Y chromosome carries the SRY gene that determines male sex; in Drosophila sex is determined by X:autosome ratio.

Q149

Minor changes at gene level are described as

A Point mutations

B Chromosomal mutations

C Reverse mutations

D Forward mutations

Correct Answer

Option A

Solution

(a) Point mutations are minor changes at the gene level — single base pair alterations.

Q150

A person with the sex chromosomes XXY suffers from

A Down syndrome

B Klinefelter syndrome

C Turner syndrome

D Gynandromorphism

Correct Answer

Option B

Solution

(b) Klinefelter syndrome (47,XXY): phenotypically male with small testes, infertility, gynecomastia.

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