A gene is said to be dominant if:

1.	It expresses its effect only in the homozygous stage
2.	It expresses only in heterozygous condition
3.	It expresses both in homozygous and heterozygous conditions
4.	It is never expressed in any condition

A plant of F₁-generation with genotype "AABbCC". On selfing of this plant what is the phenotypic ratio in F₂-generation:

1. 3 : 1

2. 1 : 1

3. 9 : 3 : 3 : 1

4. 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

A diseased man marries a normal woman. They get three daughters and five sons. All the daughters were diseased and the sons were normal. The gene of this disease is:

1. Sex-linked dominant

2. Sex-linked recessive

3. Sex-limited character

4. Autosomal dominant

There are three genes a, b, and c. The percentage of crossing over between a and b is 20%, b and c is 28% and a and c is 8%. What is the sequence of genes on a chromosome?
1. b, a, c
2. a, b, c
3. a, c, b
4. None

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

In Drosophila the XXY condition leads to femaleness whereas in human beings the same condition leads to Klinefelter's syndrome in males. It proves:

Most of the mutations are:

1. Harmful

2. Harmful and recessive

3. Beneficial

4. Dominant

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%

Which of the following discoveries resulted in a Nobel Prize:

1. X-rays induce sex-linked recessive lethal mutations

2. Cytoplasmic inheritance

3. Recombination of linked genes

4. Genetic engineering

The linkage map of the X-chromosome of fruitfly has 66 units, with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) should be:

1. 60%

2. > 50%

3. ≤ 50%

4. 100%