Principles of Inheritance and Variation Practice Questions
Class 12 · Biology · 2421 free MCQs with instant results and detailed explanations.
2421
Total
751
Easy
1212
Medium
458
Hard
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Topics in Principles of Inheritance and Variation
Genetic Disorders
637
Sex Determination
639
Linkage and Recombination
581
Mendel's Laws
564
Sample Questions from Principles of Inheritance and Variation
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
What is the primary conclusion of Mendel's Law of Segregation?
A.
Alleles for a trait separate during gamete formation.
B.
Different genes assort independently of one another.
C.
Dominant traits are always expressed.
D.
Recessive traits are never expressed.
Show Answer & Explanation
Correct Answer: A
Mendel's Law of Segregation states that during the formation of gametes, alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.
Q2
Easy
In a dihybrid cross between two heterozygous pea plants (TtYy), what is the expected phenotypic ratio of the offspring?
A.
9:3:3:1
B.
3:1
C.
1:1:1:1
D.
1:2:1
Show Answer & Explanation
Correct Answer: A
The phenotypic ratio of a dihybrid cross involving two traits is 9:3:3:1, where the ratio corresponds to the dominant and recessive traits expressed in the offspring.
Q3
Easy
What is the first law of inheritance proposed by Mendel?
A.
Law of Segregation
B.
Law of Independent Assortment
C.
Law of Dominance
D.
Law of Recessiveness
Show Answer & Explanation
Correct Answer: A
The Law of Segregation states that alleles segregate during gamete formation, leading to offspring inheriting one allele from each parent.
Q4
Medium
In a dihybrid cross between two heterozygous parents (RrYy), what is the phenotypic ratio of the offspring?
A.
9:3:3:1
B.
3:1
C.
1:2:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: A
The phenotypic ratio of a dihybrid cross is 9:3:3:1, representing the combinations of two traits.
Q5
Medium
If a plant with blue flowers (BB) is crossed with a plant with white flowers (bb), what color will the F1 generation be?
A.
Blue flowers
B.
White flowers
C.
Purple flowers
D.
Blue and white flowers
Show Answer & Explanation
Correct Answer: A
The F1 generation will all be heterozygous (Bb) and exhibit the dominant blue flower trait.
Q6
Medium
What principle states that alleles for different traits assort independently of one another during gamete formation?
A.
Law of Segregation
B.
Law of Independent Assortment
C.
Law of Dominance
D.
Law of Uniformity
Show Answer & Explanation
Correct Answer: B
The Law of Independent Assortment states that alleles for different traits segregate independently during gamete formation.
Q7
Medium
In a genetic cross, if the dominant allele is represented by 'A' and the recessive allele by 'a', what does the genotype 'Aa' represent?
A.
Homozygous dominant
B.
Homozygous recessive
C.
Heterozygous
D.
Codominant
Show Answer & Explanation
Correct Answer: C
'Aa' represents a heterozygous genotype, containing both a dominant and a recessive allele.
Q8
Hard
What is the expected phenotypic ratio in the F2 generation of a monohybrid cross according to Mendel's principles?
A.
3:1
B.
1:2:1
C.
9:3:3:1
D.
1:1
Show Answer & Explanation
Correct Answer: A
In a monohybrid cross, the F2 generation typically exhibits a phenotypic ratio of 3 dominant to 1 recessive trait.
Q9
Hard
In a dihybrid cross, what is the expected genotypic ratio in the F2 generation?
A.
9:3:3:1
B.
1:2:1
C.
3:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: A
The expected genotypic ratio in the F2 generation of a dihybrid cross is 9:3:3:1, representing combinations of both traits.
Q10
Hard
Which of the following represents an example of incomplete dominance in Mendelian genetics?
A.
Red and white flowers producing pink flowers
B.
Tall and short plants producing only tall offspring
C.
Black and white chickens producing speckled chicks
D.
Yellow and green peas producing yellow peas
Show Answer & Explanation
Correct Answer: A
Incomplete dominance occurs when the phenotype of heterozygotes is intermediate between those of the parents, such as pink flowers from red and white.
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Principles of Inheritance and Variation — Class 12 Biology Practice Questions Online
This page contains 2421 practice MCQs for the chapter Principles of Inheritance and Variation in Class 12 Biology. The questions are organized by difficulty — 751 easy, 1212 medium, 458 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit. This chapter covers 4 topics, giving you comprehensive coverage of the entire chapter.