What is the process by which characters are passed on from parent to progeny?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Variation
• Heredity
• Genetics
• Inheritance
Correct Option: D  [ Inheritance ]

Remark: Inheritance is defined as the process by which characters are passed on from parent to progeny and is the basis of heredity.

For how many years did Gregor Mendel conduct his hybridisation experiments on garden peas?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Five years (1853-1858)
• Seven years (1856-1863)
• Ten years (1856-1866)
• Three years (1860-1863)
Correct Option: B  [ Seven years (1856-1863) ]

Remark: Gregor Mendel conducted hybridisation experiments on garden peas for seven years, from 1856 to 1863, and subsequently proposed the laws of inheritance in living organisms.

What was a novel approach used by Mendel in his investigations into inheritance patterns for the first time in biology?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Observing only qualitative traits
• Applying statistical analysis and mathematical logic
• Using a small sampling size
• Conducting experiments on animals instead of plants
Correct Option: B  [ Applying statistical analysis and mathematical logic ]

Remark: During Mendel’s investigations, it was the first time that statistical analysis and mathematical logic were applied to problems in biology. This, along with a large sampling size, gave his data greater credibility.

A true-breeding line is one that:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• is heterozygous for a trait
• shows unstable trait inheritance
• has undergone continuous self-pollination and shows stable trait inheritance
• is produced by cross-pollination only
Correct Option: C  [ has undergone continuous self-pollination and shows stable trait inheritance ]

Remark: A true-breeding line is defined as one that, having undergone continuous self-pollination, shows stable trait inheritance and expression for several generations. Mendel selected 14 such true-breeding pea plant varieties.

Which of the following is NOT one of the seven contrasting traits studied by Mendel in pea plants?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Pod colour
• Stem height
• Leaf shape
• Flower position
Correct Option: C  [ Leaf shape ]

Remark: Mendel studied seven pairs of contrasting traits: Stem height, Flower colour, Flower position, Pod shape, Pod colour, Seed shape, and Seed colour. Leaf shape was not among them.

In Mendel's dihybrid cross between a plant with yellow round seeds and one with green wrinkled seeds, what was the phenotype of the F1 generation?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Green and round
• Yellow and wrinkled
• Yellow and round
• A mix of all four types
Correct Option: C  [ Yellow and round ]

Remark: Mendel found that the seeds resulting from the crossing of the parents had yellow coloured and round shaped seeds. This is because yellow colour was dominant over green and round shape was dominant over wrinkled.

What is the phenotypic ratio observed in the F2 generation of a dihybrid cross conducted by Mendel?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• 3:1
• 1:2:1
• 9:3:3:1
• 1:1:1:1
Correct Option: C  [ 9:3:3:1 ]

Remark: In the F2 generation of a dihybrid cross, the phenotypes round, yellow; wrinkled, yellow; round, green; and wrinkled, green appeared in the ratio 9:3:3:1.

Mendel's Law of Independent Assortment is based on observations from:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Monohybrid crosses
• Dihybrid crosses
• Test crosses
• Back crosses
Correct Option: B  [ Dihybrid crosses ]

Remark: Based upon observations on dihybrid crosses, which are crosses between plants differing in two traits, Mendel proposed the Law of Independent Assortment.

The Law of Independent Assortment states that:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Alleles segregate from each other during gamete formation
• When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair
• One factor in a pair is dominant over the other
• Genes on the same chromosome are always inherited together
Correct Option: B  [ When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair ]

Remark: The law states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters’.

Which of the following was NOT a reason for Mendel's work remaining unrecognised until 1900?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• His work was widely publicised and discussed
• Communication was not easy in those days
• His concept of genes as discrete units that did not blend was not accepted
• His use of mathematics to explain biology was new and unacceptable
Correct Option: A  [ His work was widely publicised and discussed ]

Remark: Mendel's work remained unrecognised for several reasons, including: poor communication which meant his work could not be widely publicised; his concept of stable, discrete genes that did not blend was not accepted; and his mathematical approach was new and unacceptable to many biologists of his time.