Biology : Principles of Inheritance and Variation

Assertion : A gamete may carry either of the traits but not both.

Reason : This is Mendel's second law or law of independent assortment.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

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

• ratio of crossing over between them

• percentage of crossing over between them

• number of crossing over between them

• none of these.

Assertion: Persons suffering from haemophilia fail to produce blood clotting factor VIII.

Reason: Prothrombin producing platelets in such persons are found in very low concentration.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

XO-chromosomal abnormality in human beings causes

• Turner's syndrome

• Down's syndrome

• Klinefelter's syndrome

• None of these

If a homozygous red-flowered plant is crossed with a homozygous white-flowered plant, the offsprings will be

• half- white flowered

• half- red flowered

• all white flowered

• all red flowered

Gene which suppresses other gene's activity but does not lie on the same locus is called as

• epistatic

• supplementary

• hypostatic

• codominant

Pure line breed refers to

• heterozygosity only

• heterozygosity and linkage

• homozygosity only

• homozygosity and self assortment

Assertion : Haemophilia is a recessive sex linked disease.

Reason : Haemophilia occurs due to mutation of a structural gene on chromosome 15.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Which one of the following pairs of features is a good example of polygenic inheritance

• Human height and skin colour

• ABO blood group in humans and flower colour of Mirabilis jalapa

• Hair pigment of mouse and tongue rolling in humans

• Human eye colour and sickle cell anaemia

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

• reciprocal cross

• dihybrid crossn

• test cross

• back cross