biology : class12 Dihybrid Cross : Dihybrid Cross, Independent Assortment : Law of Independent Assortment MCQ Questions and Answers
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Dihybrid Cross
MCQ questions and answers.
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MCQ Questions
1. A dihybrid cross involves the inheritance of how many pairs of contrasting traits?
A.
One pair
B.
Two pairs
C.
Three pairs
D.
Four pairs
Correct Answer:
Two pairs
Explanation:
A dihybrid cross studies the inheritance of two pairs of contrasting traits at the same time.
2. What is the phenotypic ratio commonly obtained in the F2 generation of a Mendelian dihybrid cross?
A.
3:1
B.
1:1
C.
9:3:3:1
D.
1:2:1
Correct Answer:
9:3:3:1
Explanation:
When two traits assort independently, the F2 phenotypes commonly occur in the ratio 9:3:3:1.
3. How many types of gametes can an individual with the genotype RrYy produce in a dihybrid cross?
A.
One
B.
Two
C.
Three
D.
Four
Correct Answer:
Four
Explanation:
The genotype RrYy produces four gamete types: RY, Ry, rY, and ry.
4. Which of the following is a possible gamete produced by an individual with genotype TtPp?
A.
TT
B.
TP
C.
Tt
D.
Pp
Correct Answer:
TP
Explanation:
A gamete receives one allele from each gene pair, so TP is a possible gamete from TtPp.
5. In a cross between RrYy and RrYy, what fraction of the offspring is expected to show both recessive traits?
A.
1/4
B.
3/16
C.
1/16
D.
9/16
Correct Answer:
1/16
Explanation:
The double recessive phenotype requires rr and yy. Each occurs with probability 1/4, so together they occur in 1/16 of the offspring.
6. In a dihybrid cross, the genotype of a true-breeding parent showing both dominant traits is represented by which expression?
A.
AABB
B.
AaBb
C.
aabb
D.
AAbb
Correct Answer:
AABB
Explanation:
A true-breeding parent with both dominant traits is homozygous dominant for both gene pairs, giving the genotype AABB.
7. What is the genotype of the F1 offspring produced by crossing AABB with aabb?
A.
AABB
B.
AaBb
C.
AAbb
D.
aaBb
Correct Answer:
AaBb
Explanation:
The AABB parent contributes AB gametes and the aabb parent contributes ab gametes, producing AaBb offspring.
8. In a test cross of a dihybrid individual AaBb with aabb, what phenotypic ratio is expected when the genes assort independently?
A.
9:3:3:1
B.
3:1
C.
1:1:1:1
D.
1:2:1
Correct Answer:
1:1:1:1
Explanation:
AaBb produces four types of gametes in equal proportions, while aabb produces only ab gametes, resulting in four phenotypes in a 1:1:1:1 ratio.
9. How many different phenotypic classes are generally found in the F2 generation of a simple dihybrid cross with complete dominance?
A.
Two
B.
Three
C.
Four
D.
Nine
Correct Answer:
Four
Explanation:
A dihybrid cross with two independently assorting traits and complete dominance produces four phenotypic classes.
10. Which parental cross is typically used to obtain a dihybrid F1 generation that is heterozygous for both traits?
A.
AABB × aabb
B.
AaBb × AaBb
C.
AAbb × aaBB
D.
Aabb × aaBb
Correct Answer:
AABB × aabb
Explanation:
Crossing homozygous dominant AABB with homozygous recessive aabb produces F1 offspring with genotype AaBb.
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Dihybrid Cross
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