12th Board Biology: Inheritance Variation Questions

Previous Year Biology Questions (12th Board)

• The document contains previous year's biology questions for the 12th board exam, specifically for the state of Jharkhand.
• The questions span the period from 2009 to 2024.
• The material focuses on the "Principle of Inheritance and Variations" topic.

Genetics (Principles of Inheritance and Variation)

• Genes coding for contrasting traits are called alleles.
• Phenotypic ratio for dihybrid cross is 9:3:3:1.
• Down's syndrome is caused by trisomy of chromosome 21.
• Klinefelter syndrome is caused by an additional X-chromosome (XXY).
• Turner syndrome is caused by missing or incomplete X-chromosome (XO).
• Haemophilia is a sex-linked disease affecting blood clotting.
• A test cross involves crossing a hybrid with a recessive individual.

Law of Dominance

• The law of dominance is explained using a suitable monohybrid cross.
• A monohybrid cross deals with a single trait.
• One allele can mask the expression of another allele.

Sex-Linked Inheritance

• Haemophilia is a sex-linked disease, predominantly affecting males.
• Sex-linked traits are associated with genes located on sex chromosomes.

Blood Groups

• There are four blood groups (A, B, AB, O).
• Blood group O is a universal donor.
• Blood group AB is a universal recipient.

Chromosomal Theory of Inheritance

• Sutton and Boveri proposed the chromosomal theory of inheritance.
• The chromosomal theory of inheritance explains the transmission of traits from parents to offspring through chromosomes.

Law of Segregation

• Mendel's law of segregation states that during gamete formation, the pairs of alleles separate, ensuring each gamete receives only one allele.
• There is no mixing of traits in the alleles.

Monohybrid and Dihybrid Crosses

• A monohybrid cross follows the inheritance of one trait.
• A dihybrid cross follows the inheritance of two traits.
• Ratios in crosses help identify patterns of inheritance (e.g., 9:3:3:1 for dihybrid, 3:1 for monohybrid).

Additional Concepts

• Multiple Alleles: Examples are blood group and hair color.
• Sex Determination: The determination of sex in humans is described.
• Mutation: The term was coined by Hugo de Vries.
• Definitions: Defining Terms like "Test Cross" and "Incomplete Dominance."

Test your knowledge with previous year questions on the topic 'Principle of Inheritance and Variations' from the 12th board Biology exam in Jharkhand. Covering questions from 2009 to 2024, this quiz will challenge your understanding of key genetic concepts and laws.