How many different types of gametes can be formed by F₁ progeny, resulting from the following cross:

AA BB CC X aa bb cc

(1) 3

(2) 8

(3) 27

(4) 64

Given below is a pedigree chart showing the inheritance of a certain sex-liniked trait in humans. 

The Trait traced in the above pedigree chart is 

(1) dominant X-linked 

(2) recessive X-linked

(3) dominant Y-linked

(4) recessive Y-linked

The "cri-du-chat" syndrome is caused by change in chromosome structure invloving

(1) deletion

(2) duplication

(3) inversion

(4) translocation

Grain colour in wheat is determined by three pairs of polygenes. Following the cross AABBCC (dark colour) X aabbcc (light colour), in F₂ generation what proportion of the progeny is likely to resemble either parent?

(1) None

(2) Less than 5 percent

(3) One third

(4) Half

Primary source of allelic variation is 

(1) independent assorment

(2) recombination

(3) mutation

(4) polyploidy

Which one of the following pairs of features is a good example of polygenic inheritance?

(1) Human height and skin colour

(2) ABO blood group in humans and flower colour of Mirabilis jalapa

(3) Hair pigment of mouse and tongue rolling in humans

(4) Human eye colour and sickle cell anaemia

Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called

(1) reciprocal cross

(2) test cross

(3) dihybrid cross

(4) back cross

Given below is a highly simplified representation of the human sex chromosomes from a karyotype.

The gene a and b could be of

(1) colour blindness and body height

(2) attached ear lobe and Rhesus blood group

(3) haemophilia and red-green colour blindness

(4) phenylketonuria and haemophilia

In which one of the following combinations (a-d) of the number of chromosomes is the present day hexaploid wheat correctly represented?

XO-chromosomal abnormality in human beings causes

(1) Turner's syndrome

(2) Down's syndrome

(3) Kilnefelter's syndrome

(4) none of these.