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

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

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

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

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

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

(1) deletion

(2) duplication

(3) inversion

(4) translocation

Given below is a pedigree chart of a family with five children. It shows the inheritance of attached ear-lobes as opposed to the free ones. The squares represent the male individuals and circles the females individuals. Which one of the foloowing conclusions drawn is correct?

(1) The parents are homozygous recessive.

(2) The trait is Y-linked.

(3) The parents are homozygous dominant.

(4) The parents are heterozygous.

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