When males produce two different types of gametes (e.g., with or without X, or X and Y), this mechanism of sex determination is called male _______.

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

• Heterogamety
• Homogamety
• Monogamety
• Polymorphism
Correct Option: A  [ Heterogamety ]

Remark: The production of two different types of gametes by males (either with or without X, or X and Y) is designated to be the example of male heterogamety.

The Law of Independent Assortment was proposed by Mendel based on his observations on _______ crosses (crosses between plants differing in two traits).

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

• Dihybrid
• Monohybrid
• Test
• Back
Correct Option: A  [ Dihybrid ]

Remark: Mendel proposed the Law of Independent Assortment based upon observations on dihybrid crosses, where the two pairs of traits segregated independently.

In a dihybrid cross, the F₂ generation exhibited a phenotypic ratio of 9 Round, Yellow : 3 Wrinkled, Yellow: 3 Round, Green : 1 Wrinkled, Green, which is a combination series of 3:1 ratio of each trait and is denoted as _______.

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

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

Remark: In the dihybrid cross, the phenotypes appeared in the ratio 9:3:3:1.

Mendel published his work on inheritance of characters in _______ but it remained unrecognised till 1900.

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

• 1865
• 1850
• 1900
• 1884
Correct Option: A  [ 1865 ]

Remark: Mendel published his work on inheritance of characters in 1865 but it remained unrecognised till 1900.

Mendel’s approach of using _______ to explain biological phenomena was totally new and unacceptable to many of the biologists of his time.

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

• Mathematics
• Cytology
• Chemistry
• Microscopy
Correct Option: A  [ Mathematics ]

Remark: Mendel’s approach of using mathematics to explain biological phenomena was totally new and unacceptable to many of the biologists of his time.

In 1900, Mendel's results were independently rediscovered by de Vries, Correns and _______.

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

• von Tschermak
• Morgan
• Watson
• Crick
Correct Option: A  [ von Tschermak ]

Remark: In 1900, three Scientists (de Vries, Correns and von Tschermak) independently rediscovered Mendel’s results on the inheritance of characters.

Due to advancements in microscopy around 1900, scientists were able to carefully observe cell division, leading to the discovery of structures in the nucleus called _______ (colored bodies).

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

• Chromosomes
• Genes
• Nucleoli
• Centromeres
Correct Option: A  [ Chromosomes ]

Remark: Advancements in microscopy led to the discovery of structures in the nucleus that appeared to double and divide, called chromosomes (colored bodies).

Walter Sutton and Theodore Boveri noted that the behaviour of chromosomes was _______ to the behaviour of genes and used this parallelism to explain Mendel’s laws.

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

• Parallel
• Opposite
• Independent
• Identical
Correct Option: A  [ Parallel ]

Remark: Walter Sutton and Theodore Boveri noted that the behaviour of chromosomes was parallel to the behaviour of genes.

The two alleles of a gene pair are located on homologous sites on _______ chromosomes.

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

• Homologous
• Autosomal
• Sex
• Sister
Correct Option: A  [ Homologous ]

Remark: The two alleles of a gene pair are located on homologous sites on homologous chromosomes.

Thomas Hunt Morgan worked with the tiny fruit fly, Drosophila melanogaster, to provide experimental verification of the _______ theory of inheritance.

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

• Chromosomal
• Dominance
• Segregation
• Biochemical
Correct Option: A  [ Chromosomal ]

Remark: Experimental verification of the chromosomal theory of inheritance was done by Thomas Hunt Morgan and his colleagues using Drosophila melanogaster.