A normal couple has seven children (2 daughters and 5 sons). Three of the sons suffer from a hereditary disorder but none of the daughters is affected. Which is the inheritance type
1. Sex-limited recessive
2. Autosomal dominant
3. Sex-linked dominant
4. Sex-linked recessive.

A woman with normal vision but with colorblind father marries a colorblind man. The fourth child of the couple is a boy. This boy
1. May or may not be colorblind
2. Must be colorblind
3. Must have normal vision
4. Will be partially colorblind due to being heterozygous

Phenotype of an organism is the result to
1. Mutations and linkages
2. Genotype and environment interactions
3. Cytoplasmic effects and nutrition
4. Environmental changes and sexual dimorphism.

Cri-du-chat syndrome in humans is caused by
1. Trisomy of 21st chromosome
2. Loss of half of short arm of chromosome 5
3. Loss of half of long arm of chromosome 5
4. Fertilization of an XX egg by a normal Y- bearing sperm.

Both sickle cell anaemia and Huntington’s chorea are
1. Virus related diseases
2. Bacteria related diseases
3. Congenital disorders
4. Pollution induced disorders

R and Y genes of Maize lie very close to each other. When RRYY and rryy genotype are hybridised, F2 generation will show
1. Segregation in 9: 3 : 3 : 1 ratio
2. Segregation is 3 : 1 ratio
3. Higher number of parental types
4. Higher number of recombinant types

Telomeres with repetitive DNA sequences
1. Act as replicons
2. Are transcription initiators
3. Help in chromosome pairing
4. Prevent chromosome loss.

In pea, yellow seed colour is dominant over green colour. Heterozygous yellow seeded plant is crossed with green seeded plant. The ratio of yellow & green seeded offspring will be
1. 9 : 1
2. 1 : 3
3. 3 : 1
4.50 : 50

Which one of the following is a wrong statement regarding mutations?
1. Deletion and insertion of base pairs cause frame-shift mutations
2. Cancer cells commonly show chromosomal aberrations
3. UV and Gamma rays are mutagens
4. Change in a single base pair of DNA does not cause mutation

F₂ generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1 It represents a case of :
1. Co-dominance
2. Dihybrid cross
3. Monohybrid cross with complete dominance
4. Monohybrid cross with incomplete dominance