A dihybrid cross produces the following progeny - AaBb = 240; Aabb =754; aaBb = 746; aabb = 260. What is the distance between the two genes on the chromosome?

(1) 12.5 map units

(2) 1 map unit

(3) 20 map units

(4) 25 map units

Which of the following statements is not true of two genes that show 50% recombination frequency?

(1) the genes may be on different chromosomes 

(2) the genes are tightly linked

(3) the genes show independent assortment

(4) If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis

Mutations can be induced with 

(1) IAA

(2) ethylene

(3) gama radiations

(4) infra red radiations

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.

A diagramatic representation of karyotype of a species is referred to as its

(1) idiogram

(2) hologram

(3) karyogram

(4) Both 1 and 3

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

(1) transition

(2) translocation

(3) deletion

(4) transversion

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

(1) deletion

(2) duplication

(3) inversion

(4) translocation

Primary source of allelic variation is 

(1) independent assorment

(2) recombination

(3) mutation

(4) polyploidy

The distance between two genes in a chromosome is measured in cross-over units which represent

(1) ratio of crossing over between them

(2) percentage of crossing over between them

(3) number of crossing over between them

(4) none of these

Percentage of recombination between A and B is 9%, A and C is 17%, B and C is 26%, then the arrangement of genes is 

(1) ABC

(2) ACB

(3) BCA

(4) BAC