Biology : Principles of Inheritance and Variation

In an organism, tall phenotype is dominant over recessive dwarf phenotype and the alleles are designated as T and t, respectively. Upon crossing two different individuals, total 250 offsprings were obtained, out of which 124 displayed tall phenotype and rest were dwarf Thus, the genotype of the parents were

• TT $\times$ TT

• TT $\times$ tt

• Tt $\times$ Tt

• Tt $\times$ tt

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

• the genes may be on different chromosomes

• the genes are tightly linked

• the genes show independent assortment

• if the genes are present on the same chromosome, they undergo more than one cross overs in every meiosis

If two persons with 'AB' blood group marry and have sufficiently large number of children, these children could be classified as 'A' blood group : 'AB' blood group : 'B' blood group in 1 : 2 : 1 ratio. Modern technique of protein electrophoresis reveals presence of both 'A' and 'B' type proteins in 'AB' blood group individuals. This is an example of

• codominance

• incomplete dominance

• partial dominance

• complete dominance

Which Mendelian idea is depicted by a cross in which the F₁ generation resembles both the parents?

• Incomplete dominance

• Law of dominance

• Inheritance of one gene

• Codominance

The incorrect statement with regard to haemophilia is

• it is a sex-linked disease

• it is a recessive disease

• it is a dominant disease

• a single protein involved in the clotting of blood is affected

If both parents are carriers for thalassemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?

• No chance

• 50%

• 25%

• 100%

The frequency of crossing-over occurring between two genes located on the same chromosome depends on

• length of the chromosome

• position of the centromere

• activities of two genes

• distance between two genes

Anish is having colour blindness and married to Sheela, who is not colourblind. What is the chance that their son will have the disease?

• 100%

• 50%

• 25%

• 0%

In a plant species, flower colour yellow is dominant over white and fruit shape round is dominant over elongated. Crossing was performed between two pure lines - one having yellow-flower and round-fruit and another with white-flower and elongated-fruit. About 20 plants survived in F₁ progeny. Plants of F₁ were allowed to self-fertilise and about 960 plants survived in F₂. If the traits follow Mendelian inheritance, the number of plants would have yellow-flower and round-fruit in F₁ and F₂ are respectively

• 20, 960

• 20, 540

• 10, 180

• 10, 60

A set of genes will be in a complete linkage when the progeny phenotypes for parental (P) and recombinant (R) types are

• P = 0%, R =100%

• P = 50%, R = 50%

• P < 50%, R > 50%

• P = 100%, R = 0%