Principles of Inheritance and Variation

Differentiate between incomplete dominance and codominance, giving one example of each. Work out a cross showing the inheritance of ABO blood groups and explain how it demonstrates both multiple allelism and codominance.

What is a test cross? How is it useful in determining the genotype of an organism showing a dominant phenotype?

State Mendel's Law of Independent Assortment. Using a dihybrid cross, work out the F₂ phenotypic ratio and explain how the law is verified by a test cross.

What is pedigree analysis? Mention any two conclusions that can be drawn from the study of a pedigree chart for a genetic disorder.

Explain the pattern of inheritance of haemophilia in humans with the help of a cross between a carrier woman and a normal man.

(a) What is aneuploidy? Explain how it differs from polyploidy. (b) Describe the chromosomal basis and symptoms of Down's syndrome and Turner's syndrome.

What is linkage? How did Morgan's experiments on Drosophila demonstrate linkage and recombination?

State Mendel's Law of Dominance and Law of Segregation.

A dihybrid cross is made between a pure-breeding round yellow seed pea plant (RRYY) and a pure-breeding wrinkled green (rryy) one. Work out the F₁ and F₂ generations. State the phenotypic ratio obtained in F₂ and the law it illustrates.

Why is human male said to be heterogametic while the female is homogametic?

How many marks is Principles of Inheritance and Variation worth in the Class 12 board exam?

Around 10 marks of the 70-mark CBSE Biology theory paper, based on the official unit-wise weightage. Monohybrid/dihybrid crosses + pedigree — practise the numericals daily.

Is Principles of Inheritance and Variation easy or hard?

It's rated hard — one of the tougher chapters in Class 12 Biology. Most students need about 6 hours to cover it well.

What should I focus on in Principles of Inheritance and Variation?

Going by the board papers themselves, the recurring areas are Incomplete Dominance & Codominance, Test Cross, Law of Independent Assortment, Pedigree Analysis, Sex-linked Inheritance — that's where the marks actually sit.

What questions come from Principles of Inheritance and Variation in board exams?

Between 2018–2024, CBSE board papers asked questions from this chapter on Incomplete Dominance & Codominance, Test Cross, Law of Independent Assortment, Pedigree Analysis — 1- to 5-mark questions.