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

If both parents are carrier for thalessemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child ?
1. 50%
2. 25 %
3. 100%
4. no chance

Which of the following statements is not true of two genes that show 50% recombination frequency?
1. The genes are tightly linked
2. The genes show independent assortment
3. If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis
4.The genes may be on different chromosomes

Fruit colour in squash is an example of :
1. Recessive epistasis
2. Dominant epistasis
3. Complementary genes
4. Inhibitory genes