UnIT-VII : GEnETICS AnD EVOLUTIOn
ChApTEr-5 : prInCIpLES OF
InhErITAnCE AnD VArIATIOnMultiple Choice Questions- If both parents are carriers for thalassaemia, which is
an autosomal recessive disorder, what are the chances
of pregnancy resulting in an affected child?
(a) 25% (b) 100%
(c) No chance (d) 50% - A child’s blood group is ‘O’. His parents’ blood groups
cannot be
(a) A and B (b) A and A
(c) AB and O (d) B and O. - Down’s syndrome in humans is due to
(a) three ‘X’ chromosomes
(b) three copies of chromosome 21
(c) monosomy
(d) two ‘Y’ chromosomes. - If a cross between two individuals produces offsprings
with 50% dominant character (A) and 50% recessive
character (a), the genotypes of parents are
(a) Aa × Aa (b) Aa × aa
(c) AA × aa (d) AA × Aa. - Which one of the following conditions correctly
describes the manner of determining the sex?
(a) Homozygous sex chromosomes (ZZ) determine
female sex in birds.
(b) XO type of sex chromosomes determine male sex
in grasshopper.
(c) XO condition in humans as found in Turner’s
syndrome, determines female sex.
(d) Homozygous sex chromosomes (XX) produce
male in Drosophila.- In a typical Mendelian dihybrid cross, one parent is
homozygous for both dominant traits and another
parent is homozygous for both recessive traits. In
the F 2 generation , both parental combinations and
recombinations appear. The phenotypic ratio of
parental combinations to recombinations is
(a) 10 : 6 (b) 12 : 4
(c) 9 : 7 (d) 15 : 1. - The existence of non-beneficial alleles in heterozygous
genotype within a population is
(a) genetic load (b) genetic drift
(c) genetic flow (d) selection. - Due to nondisjunction of chromosomes during
spermatogenesis, some sperms carry both sex
chromosomes (22A + XY) and some sperms do not
carry any sex chromosome (22A + O). If these sperms
fertilise normal eggs (22A + X), what types of genetic
disorders appear among the offsprings?
(a) Klinefelter’s syndrome and Turner’s syndrome
(b) Down’s syndrome and Klinefelter’s syndrome
(c) Down’s syndrome and Turner’s syndrome
(d) Down’s syndrome and Cri-du-chat syndrome