The genetic disorder due to the presence of an extra copy of chromosome 21 is: MCQ with Answer and Explanation

The genetic disorder due to the presence of an extra copy of chromosome 21 is:
A. Phenylketonuria
B. Turner's syndrome
C. Klinefelter's syndrome
D. Down syndrome
Answer: Option D
Solution (By JKExamLibrary)
Down syndrome (trisomy 21) is an autosomal aneuploidy caused by nondisjunction resulting in three copies of chromosome 21. It is characterized by intellectual disability, flat facial profile, protruding tongue, and simian crease. Turner's syndrome is monosomy X (45, X). Klinefelter's is 47, XXY. Phenylketonuria is an inborn error of metabolism (autosomal recessive) due to deficiency of phenylalanine hydroxylase.

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More Biology Questions

Question #1
Which of the following statements about the human eye is correct?
A. The pupil is an opening that cannot change size.
B. The blind spot contains a high density of cones.
C. The lens changes shape to focus on near or distant objects.
D. The fovea has the highest concentration of rods.

Correct Answer: Option C


Explanation:
Accommodation involves lens shape change via ciliary muscles. The blind spot lacks photoreceptors; fovea has high cone density; pupil adjusts via iris.

This question belongs to: Science Biology
Question #2
Consider statements about scientists: 1. Robert Hooke discovered cells. 2. Antonie van Leeuwenhoek discovered bacteria. 3. Charles Darwin proposed the cell theory. Which are correct?
A. 1 and 3 only
B. 1, 2 and 3
C. 2 and 3 only
D. 1 and 2 only

Correct Answer: Option D


Explanation:
Robert Hooke, in 1665, observed dead cork tissue under a microscope and coined the term 'cell' for the box-like structures he saw. Antonie van Leeuwenhoek, using his superior single-lens microscopes in the 1670s, was the first to observe and describe living microorganisms, including bacteria and protozoa. Charles Darwin proposed the theory of evolution by natural selection; the cell theory was proposed by Matthias Schleiden and Theodor Schwann. Thus, statements 1 and 2 are correct.

This question belongs to: Science Biology
Question #3
Consider the following statements about the liver:
1. It stores glycogen.
2. It secretes bile.
3. It produces insulin.
Which of the above is/are correct?
A. 1 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 2 and 3 only

Correct Answer: Option C


Explanation:
The liver stores glycogen and produces bile. Insulin is produced by the beta cells of the pancreas. So 3 is incorrect.

This question belongs to: Science Biology