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.

Test cross involves
1. Crossing between two genotypes with dominant trait
2. Crossing between two genotypes with recessive trait
3. Crossing the F₁ hybrid with double recessive genotype
4. Crossing between two F₁ hybrids.

Lack of independent assortment between two genes A and B would be due to
1. Crossing over
2. Linkage
3. Repulsion
4. Recombination.

Recessive gene present on one X- chromosome of humans will be
1. Lethal
2. Sublethal
3. Expressed in males
4. Expressed in females.

Genotype of hybrid is known by crossing
1. F₂ progeny with female parent
2. F₁ × F₁
3. Crossing F₁ with recessive parent
4. F₂ with recessive parent.

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

A human male produces diallelic sperms in equal proportion AB, Ab, aB, and ab. The genotype of the person would be: