1. What phenotypic ratio is typically obtained in the F2 generation of a Mendelian dihybrid cross?
A.
3:1
B.
1:2:1
C.
9:3:3:1
D.
1:1
Correct Answer:
9:3:3:1
Explanation:
A typical dihybrid cross involving two independently assorting traits produces the F2 phenotypic ratio 9:3:3:1.
2. In the 9:3:3:1 ratio, what does the number 9 represent?
A.
Individuals showing both recessive traits
B.
Individuals showing both dominant traits
C.
Individuals showing only the first dominant trait
D.
Individuals showing only the second dominant trait
Correct Answer:
Individuals showing both dominant traits
Explanation:
The 9 represents offspring that show the dominant phenotype for both traits.
3. In a dihybrid F2 generation with 160 offspring, how many are expected to show both recessive traits according to the 9:3:3:1 ratio?
A.
10
B.
20
C.
30
D.
90
Correct Answer:
10
Explanation:
The both-recessive class is 1/16 of the offspring. One-sixteenth of 160 is 10.
4. Which fraction of the F2 offspring shows the phenotype represented by the 3 in a 9:3:3:1 ratio?
A.
9/16
B.
3/16
C.
1/16
D.
12/16
Correct Answer:
3/16
Explanation:
Each class represented by 3 accounts for 3 out of 16 total parts, or 3/16 of the F2 offspring.
5. If 16 offspring are produced in the F2 generation of a dihybrid cross, how many are expected to show both dominant phenotypes?
A.
1
B.
3
C.
9
D.
16
Correct Answer:
9
Explanation:
The both-dominant phenotype is represented by 9 in the 9:3:3:1 ratio, so 9 out of 16 offspring are expected.
6. In the 9:3:3:1 ratio, what do the two groups represented by 3 indicate?
A.
Both dominant and both recessive phenotypes
B.
One dominant phenotype combined with one recessive phenotype
C.
Only individuals with recessive alleles
D.
Only individuals with identical alleles
Correct Answer:
One dominant phenotype combined with one recessive phenotype
Explanation:
The two groups of 3 represent offspring showing a dominant phenotype for one trait and a recessive phenotype for the other trait.
7. A 9:3:3:1 ratio contains how many total equal parts?
A.
9
B.
12
C.
16
D.
24
Correct Answer:
16
Explanation:
Adding the four parts gives 9 + 3 + 3 + 1 = 16 total parts.
8. In a dihybrid F2 ratio of 9:3:3:1, what percentage of offspring is expected to show both recessive phenotypes?
A.
6.25%
B.
18.75%
C.
37.5%
D.
56.25%
Correct Answer:
6.25%
Explanation:
The both-recessive class is 1/16. Converting 1/16 to a percentage gives 6.25%.
9. If a dihybrid cross produces 320 F2 offspring, how many are expected to show both dominant phenotypes?
A.
20
B.
60
C.
180
D.
240
Correct Answer:
180
Explanation:
The both-dominant class is 9/16 of the offspring. 9/16 multiplied by 320 equals 180.
10. Which phenotype class is represented by the smallest number in the 9:3:3:1 ratio?
A.
Both dominant traits
B.
Only the first dominant trait
C.
Only the second dominant trait
D.
Both recessive traits
Correct Answer:
Both recessive traits
Explanation:
The smallest class is represented by 1, which corresponds to offspring showing both recessive phenotypes.
Short questions are currently unavailable for this page.