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%

Two crosses between the same pair of genotypes or phenotypes in which the sources of the gametes are reversed in one cross is known as:

1. Test cross

2. Reciprocal cross

3. Dihybrid cross

4. Reverse cross

The genes controlling the seven pea characters studied by Mendel are now known to be located on how many different chromosomes:

1. Seven

2. Six

3. Five

4. Four

Which one of the following traits of garden peas studied by Mendel was a recessive feature?

Which one of the following conditions, though harmful in itself, is also a potential saviour from a mosquito-borne infectious disease?

Pattern baldness, moustaches, and beard in human males are examples of:

1. Sex-linked traits

2. Sex-limited traits

3. Sex-differentiating traits

4. Sex-determining traits

When a cluster of genes shows linkage behaviour they:

1. Do not show a chromosome map

2. Show recombination during meiosis

3. Do not show independent assortment

4. Induce cell division

Christmas disease is another name for:

1. Haemophilia B

2. Hepatitis B

3. Down's syndrome

4. Sleeping sickness