ABO blood groups in humans are controlled by the gene I. It has three alleles — I^A, I^B and i. Since there are three different alleles, six different genotypes are possible. How many phenotypes can occur?

(1) Three

(2) One

(3) Four

(4) Two

Select the correct statement from the ones given below with respect to dihybrid cross.

(1) Tightly linked genes on the same chromosome show higher recombinations

(2) Genes far apart on the same chromosome show very few recombinations

(3) Genes loosely linked on the same chromosome show similar recombinations as the tightly linked ones

(4) Tightly linked genes on the same chromosome show very few recombinations.

Sickel cell anaemia is

(1) an autosomal linked dominant trait 

(2) caused by substitution of valine by glutamic acid in the β-globin chain of haemoglobin.

(3) caused by a change in base pair of DNA

(4) characterized by elongated sickle like RBCs with a nucleus. 

Select the incorrect statement from the following

(1) linkage is an exception to the principle of independent assortment in heredity

(2) galactosemia is an inborn error of metabolism

(3) small population size results in random genetic drift in a population

(4) baldness is a sex limited trait

Which one of the following condition in human is correctly matched with its chromosomal abnormality/linkage?

(1) Klinefelter's syndrome—44 autosomes + XXY

(2) Colourblindness —Y-linked

(3) Erythroblastosis foetalis— X-linked

(4) Down syndrome—44 autosomes + XO

A human male produces sperms with the genotypes AB, Ab, aB and ab pertaining to two diallelic characters in equal proportions. What is the corresponding genotype of this person ?

(1) AaBb

(2) AaBB

(3) AABb

(4) AABB

Inheritance of skin colour in humans is an example of :

(1) chromosomal aberration

(2) point mutation

(3) polygenic inheritance 

(4) codominance

Two genes R and Y are located very close on the chromosomal linkage map of maize plant. When RRYY and rryy genotypes are hybridised, then F₂ segregation will show :

(1) higher number of the recombinant types

(2) segregation in the expected 9 : 3 : 3 : 1 ratio

(3) segregation in 3 : 1

(4) higher number of the parental types

A common test to find the genotype or hybrid is by :

(1) crossing of one F₂ progeny with male parent

(2) crossing of one F₂ progeny with female parent

(3) studying the sexual behaviour of F₁ progenies

(4) crossing of one F₁ progeny with recessive parent

In pea plants, yellow seeds are dominant to green. If heterozygous yellow seeded plant is crossed with a green seeded plant, what ratio of yellow and green plants would you expect in F₁ generation ?

(1) 50 : 50

(2) 9 : 1

(3) 1 : 3

(4) 3 : 1