Which one of the following symbols and its representation, used in the human pedigree analysis is correct?

1.	= Mating between relatives
2.	= Unaffected male
3.	= Unaffected female
4.	= male affected

If a chiasma forms between the loci of genes A and B in 20% of the tetrads of an individual of genotype AB/ab, the percentage of gametes expected to be Ab is:

1. 40

2. 20

3. 10

4. 5

Phenotype of an organism is the result of:

1. mutations and linkages

2. cytoplasmic effects and nutrition

3. environmental changes and sexual dimorpgism

4. genotype and environment interactions

Both sickle cell anaemia and Huntington’s chorea are:

1. bacteria-related diseases.

2. congenital disorders

3. pollutant-induced disorders

4. virus-related diseases

The dominant epistasis ratio is:

1. 9:3:3:1

2. 12:3:1

3. 9:3:4

4. 9:6:1

Select the correct statement from the options given below with respect to the dihybrid cross.

1. Tightly linked genes on the same chromosome show higher recombination

2. Genes for apart on the same chromosomes show very few recombination

3. Genes that are loosely linked on the same chromosomes. Show similar recombination as lightly linked ones

4. Tightly linked genes on the same chromosomes show very few recombination

Two genes R and y are located very close on the chromosome linkage map on maize plant. When RRYY and rryy genotypes are hybridized, then F₂ segregation will show:

1. Higher number of the recombinant types

2. Segregation with expected 9:3:3:1 ratio

3. Segregation is 3:1 ratio

4. Higher number of parental types

A woman with two genes (one on each X-chromosome) for haemophilia and one gene for colour blindness on the X-chromosome marries a normal man. How will the progeny be?
 

A hereditary disease which is never passed on from father to son is:

1. X-chromosomal linked disease

2. Autosomal linked disease

3. Y-chromosomal linked disease

4. None of the above

A polygenic inheritance in human beings is:

1. skin colour

2. sickle cell anaemia

3. colour blindness

4. phenylketonuria