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Class 12 Principles of Inheritance and Variation worksheet
CBSE Biology. Monohybrid and dihybrid ratios, test cross, ABO groups, sex-linked crosses, disorders. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
Mendel worked on the garden pea, Pisum sativum, between:
- 1800 and 1810
- 1950 and 1960
- 1900 and 1910
- 1856 and 1863
Answer
(d) 1856 and 1863
- 2.
In pea, round seeds (R) are dominant over wrinkled seeds (r). In the cross rr × Rr, the fraction of offspring with round seeds is:
- 1/2
- 1/4
- 3/4
- 0
Answer
(a) 1/2
gametes r × R, r
- 3.
In the cross AaII × AAii, the probability of an offspring with genotype AAIi is:
- 1/4
- 1/16
- 1/2
- 1/8
Answer
(c) 1/2
P(AA) × P(Ii) = 1/2 × 1
Section B · short answer
- 4.
State Mendel's law of segregation.
Answer
The two alleles of a gene, present together in an individual, separate (segregate) during gamete formation, so each gamete gets only one of them.
- 5.
A pea plant pure for violet flowers and tall stems (VVTT) is crossed with one pure for white flowers and dwarf stems. The F1 is selfed and gives 480 F2 plants. How many of each phenotype are expected?
Answer
violet flowers, tall stems: 270; violet flowers, dwarf stems: 90; white flowers, tall stems: 90; white flowers, dwarf stems: 30
9 : 3 : 3 : 1
Section C · long answer
- 6.
Explain a monohybrid cross with the example of tall and dwarf pea plants.
Answer
TT (tall) × tt (dwarf) gives Tt F1 plants, all tall. Selfing the F1 (Tt × Tt) gives TT, Tt and tt in the ratio 1 : 2 : 1, i.e. 3 tall : 1 dwarf. This shows dominance (T masks t) and segregation (the two alleles separate in gametes and recombine at fertilisation).
Fresh sheets for your child
In the app, every Principles of Inheritance and Variation sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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