Cri-du-chat syndrome in humans is caused by the :

(1) fertilization of an XX egg by a normal Y-bearing sperm

(2) loss of half of the short arm of chromosome 5

(3) loss of half of the long arm of chromosome 5

(4) trisomy of 21st chromosome.

Sickle cell anaemia has not been eliminated from the African population because :

(1) it is controlled by recessive genes

(b) it is not a fatal disease

(3) it provides immunity against malaria

(4) it is controlled by a dominant genes

Which of the following shows linkage group in coupling phase?

(1)  $\underline{A B}$
$\overline{a b}$

(2)  $\underline{A b }$
$\overline{a B}$

(3)  $\underline{A b}$
$\overline{a b}$

(4)  $\underline{a B}$
$\overline{a b}$

A pure breeding pea plant with the dominant phenotype of character A and recessive phenotype of character B was crossed with another pure breeding plant with the recessive phenotype of character A and dominant phenotype character B. Offspring of this cross was crossed with a homozygous recessive for both the characters A and B. The following results were obtained. 

22 were phenotypically dominant of A and recessive of B

22 were phenotypically recessive for both A and B

22 were phenotypically recessive for A and dominant for B

22 were phenotypically dominant for both A and B 

The results show that 

(1) genes A and B are linked

(2) independent segregation of genes A and B

(3) Mendelian dihybrid inheritance

(4) polygenic inheritance.

An inherited character and its detectable variant is termed as

(1) unit factor

(2) trait

(3) genetic profile

(4) genotypic charcter

Which of the following is not an autosomal genetic disorder ?

(1) Sickle-cell anaemia

(2) Cystic fibrosis

(3) Haemophilia

(4) Huntington's disease

Study the pedigree chart of a family showing the inheritance of myotonic dystrophy.

The trait under study is 

1. dominant X-linked

2. recessive X-linked

3. autosomal dominant

4. recessive Y-linked.

The ratio in a dihybrid test cross between two individuals is given by

(1) 2:1

(2) 1:2:1

(3) 3:1

(4) 1:1:1:1

A point mutation comprising the substitution of a purine by pyrimidine is called

(1) transition

(2) translocation

(3) deletion

(4) transversion

Pure line breed refers to

(1) heterozygosity only

(2) heterogyzosity and linkage

(3) homozygosity only

(4) homozygosity and self assortment.