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

1.	Turner syndrome	2.	Down syndrome
3.	Superfemaleness	4.	Triploidy

A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance might be the reason for this disease?

1. Sex-limited recessive

2. Autosomal dominant

3. Sex-linked recessive

4. Sex-linked dominant

If a female having gene for haemophilia and colour-blindness on one X-chromosome marries a normal male, then what are the chances in their offspring?
1. 50% sons diseased and 50% normal
2. All normal offspring
3. 100% daughters are carrier
4. 100% sons diseased

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

ABO blood group has:
1.  Two codominant and one recessive allele
2.  Two codominant and two recessive allele
3.  Two incompletely dominant genes
4.  Two pseudo alleles

A normal woman, whose father was colour-blind is married to a normal man. The sons would be:
1. 50% colour-blind
2. All normal
3. All colour-blind
4. 75 % colour-blind 

Lack of independent assortment of two genes A and B in the fruit fly Drosophila is due to:

1. Recombination

2. Linkage

3. Crossing over

4. Repulsion 

In a plant red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). If a plant with RRTt genotype is crossed with a plant that is rrtt:

1. 50% will be tall with red fruit

2. 75% will be tall with red fruit

3. All the offspring will be tall with red fruit

4. 25% will be tall with red fruit

What change occurs by changing one base in DNA:
1.  Always a change of one amino acid in protein
2.  Change in complex sequence of amino acid
3.  Always a change in property of protein
4.  Does not necessarily change the phenotype