biology : class12 F2 Generation : Dihybrid Cross, Independent Assortment : Law of Independent Assortment MCQ Questions and Answers
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F2 Generation
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MCQ Questions
1. In the F2 generation of a typical dihybrid cross AaBb × AaBb, what is the phenotypic ratio?
A.
3:1
B.
9:3:3:1
C.
1:2:1
D.
1:1:1:1
Correct Answer:
9:3:3:1
Explanation:
The F2 generation from a self-cross of two double heterozygotes, AaBb × AaBb, shows the characteristic dihybrid phenotypic ratio of 9:3:3:1.
2. In the F2 generation of AaBb × AaBb, what fraction of the offspring is expected to show both dominant traits?
A.
1/16
B.
3/16
C.
9/16
D.
12/16
Correct Answer:
9/16
Explanation:
The class showing both dominant traits has the genotype pattern A_B_ and represents 9 out of 16 offspring in the F2 generation.
3. How many different types of gametes can an F1 individual with genotype AaBb produce for forming the F2 generation?
A.
1
B.
2
C.
3
D.
4
Correct Answer:
4
Explanation:
An AaBb individual produces four types of gametes—AB, Ab, aB, and ab—which combine to form the F2 generation.
4. In the F2 generation of AaBb × AaBb, what proportion is expected to have both recessive traits?
A.
1/16
B.
3/16
C.
9/16
D.
4/16
Correct Answer:
1/16
Explanation:
Both recessive traits appear only in the aabb genotype, which occurs in 1 out of 16 F2 offspring.
5. Which parental cross directly produces an F2 generation in a standard dihybrid cross?
A.
AABB × aabb
B.
AaBb × AaBb
C.
AAbb × aaBB
D.
AaBB × AAbb
Correct Answer:
AaBb × AaBb
Explanation:
The F2 generation is produced by crossing or selfing the F1 dihybrid individuals, which are typically AaBb × AaBb.
6. In the F2 generation of AaBb × AaBb, what fraction is expected to show one dominant trait and one recessive trait?
A.
3/16
B.
6/16
C.
9/16
D.
1/16
Correct Answer:
6/16
Explanation:
The two phenotypic classes with one dominant and one recessive trait each occur at 3/16, giving a combined proportion of 6/16.
7. What is the expected genotypic ratio in the F2 generation of AaBb × AaBb?
A.
1:2:1
B.
3:1
C.
1:2:1:2:4:2:1:2:1
D.
9:3:3:1
Correct Answer:
1:2:1:2:4:2:1:2:1
Explanation:
The F2 dihybrid cross produces nine genotype classes in the ratio 1:2:1:2:4:2:1:2:1.
8. In a 16-box Punnett square for AaBb × AaBb, how many boxes represent the F2 phenotype with both dominant traits?
A.
3
B.
4
C.
9
D.
12
Correct Answer:
9
Explanation:
The both-dominant phenotype occurs in 9 of the 16 possible F2 combinations, represented by the genotype pattern A_B_.
9. What percentage of offspring in the F2 generation of AaBb × AaBb is expected to show the phenotype with both recessive traits?
A.
6.25%
B.
18.75%
C.
25%
D.
56.25%
Correct Answer:
6.25%
Explanation:
The aabb class occurs in 1/16 of the F2 generation, and 1/16 expressed as a percentage is 6.25%.
10. In the F2 generation of a dihybrid cross, what is the expected ratio of offspring with dominant seed color and recessive seed shape to offspring with recessive seed color and dominant seed shape?
A.
1:1
B.
3:3
C.
9:3
D.
3:1
Correct Answer:
1:1
Explanation:
Each of these two phenotypic classes occurs in 3/16 of the F2 generation, so their ratio is 3:3, which simplifies to 1:1.
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