Question:

A person with the sex chromosomes XXY suffers from

Updated On: May 5, 2024

gynandromorphism
Klinefelter's syndrome
Down's syndrome
Turner's syndrome.

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The Correct Option is B

Solution and Explanation

Klinefelter's syndrome is an aneuploid condition with 3 sex chromosomes (trisomy). Klinefelter's syndrome is caused by XXY genotype. This genotype results from the union of a nondisjunct XX egg and a normal Y sperm or normal X egg and abnormal XY sperm. The individual has 47 chromosomes (2n + 1). The person having Klinefelter's syndrome is a sterile male with small testes, unusually long legs, obesity, and sparse body hair, and with many female characteristics such as breasts. The victim usually has normal intelligence. The more the X chromosomes, the greater is the mental defect. Klinefelter's syndrome occurs about once in 2000 live births. Turner's syndrome is formed by the union of an abnormal O egg and a normal X sperm or a normal egg and an abnormal O sperm. The individual has 45 chromosomes (44 + X). Down's syndrome is caused by the presence of an extra chromosome number 21. Gynandromorphism is a phenomomenon by which one part of the body of an animal is male and the other part is female.

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Questions Asked in NEET exam

Match List I with List II:

List I		List II
A	Robert May	I	Species-Area relationship
B	Alexander von Humboldt	II	Long term ecosystem experiment using out door plots
C	Paul Ehrlich	III	Global species diversity at about 7 million
D	David Tilman	IV	Rivet popper hypothesis

Choose the correct answer from the options given below:

NEET (UG) - 2024
Species diversity

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List I	List II
A	Mesozoic Era	I	Lower invertebrates
B	Proterozoic Era	II	Fish & Amphibia
C	Cenozoic Era	III	Birds & Reptiles
D	Paleozoic Era	IV	Mammals

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Concepts Used:

Principles of Inheritance and Variation - Mutation

A Mutation is a change in the sequence of our DNA base pairs caused by numerous environmental stimuli such as UV light or mistakes during DNA replication. Germline mutations take place in the eggs and sperm and can be passed onto offspring, whereas somatic mutations take place in body cells and are not passed on.

Types of Mutations

There are three types of mutations, which are as follows:

Silent mutation

It refers to any change in DNA sequence that has no effect on the amino acid sequence in a protein or the functions that a protein performs. There is no phenotypic indication that a mutation has occurred.

Nonsense mutation

When there is a change in the sequence of base pairs due to a point mutation, that results in a stop codon. This leads to a protein that is either shortened or non-functional.

Missense mutation

A missense mutation occurs when a point mutation causes a change in the codon, which then codes for another amino acid.

The mutation is caused by the following factors:

Internal Causes

When DNA copies incorrectly, the majority of mutations occur. Evolution occurs as a result of all of these mutations. DNA makes a copy of itself during cell division. When a copy of DNA isn't flawless, it's called a mutation since it differs somewhat from the original DNA.

External Causes

When certain chemicals or radiations are used to break down DNA, it causes the DNA to break down. The thymine dimers are broken by UV radiation, resulting in altered DNA.