Reason for trisomy in Down's syndrome is:
1.  Non-disjunction during sperm formation
2.  Non-disjunction during egg formation
3.  Non-disjunction at the time of egg or sperm formation
4.  Addition of one extra chromosome during mitosis

Mental retardation in man occurs due to:
1. Loss of one X chromosome
2. Addition of one X chromosome
3. Slight growth in Y
4. Overgrowth in Y

Mangolian idiots are due to trisomy in the 21^st chromosome is called:

1. Down's syndrome

2. Turner's syndrome

3. Kleinfelters syndrome

4. Triplex syndrome

Male XX and female XY sometime occur due to:
1.  Deletion
2.  Transfer of segments in X and Y chromosomes
3.  Aneuploidy
4.  Hormonal imbalance

Which of the following is the correct match:

1. Down Syndrome = 21st Chromosome

2. Sickel cell anaemia = X – Chromosome

3. Haemophilia = Y – Chromosome

4. Parkinson Disease = X & Y Chromosomes

Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of offspring produced by an affected mother and a normal father would be affected by this disorder:

1. 100%

2. 75%

3. 50%

4. 25%

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