This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Incomplete Dominance and Codominance”.
1. In incomplete dominance__________________
a) Phenotype of both allele is expressed
b) Phenotype of only one allele is expressed
c) Phenotype of neither of the alleles are expressed
d) Phenotype of both allele is partially expressed
View Answer
Explanation: In case of incomplete dominance the expression of the phenotype of neither of the allele is complete; although one is more expressed than another.
2. Codominance and incomplete dominance is the same thing.
a) True
b) False
View Answer
Explanation: In case of codominance both the alleles of heterozygote are expressed whereas in case of incomplete dominance one of the allele is expressed incompletely in case of heterozygous condition.
3. Choose the wrong one out.
a) Codominant genes are never haplosufficient
b) Dominant phenotype is expressed when a gene is haplosufficient
c) Incomplele dominance is the presence of haplosufficiency
d) In homozygous condition an allele can express its phenotype be it the dominant or recessive allele in nature
View Answer
Explanation: Haplosufficiency is the condition when an allele can express itself fully and produce its phenotype completely even in heterozygous condition. Incomplete dominance results from lack of haplosufficiency.
4. A white and a black chicken give an egg. What is the probability of the progeny born being Andalusian?
a) 1/6
b) 1/4
c) 1/2
d) 1
View Answer
Explanation: As the progeny will receive one plumage color allele from each of its parents its resultant genotype will be heterozygote. Heterozygous chickens are Andalusian so the probability is 1 or it is certain.
5. In case of incomplete dominance monohybrid F1 ________________ is 1:2:1.
a) Genotype
b) Phenotype
c) Bothe genotype and phenotype
d) The ratio is wrong
View Answer
Explanation: In case of incomplete dominance the phenotype and genotypes are same and the ratio is 1:2:1. This is because the heterozygote has a distinctly different appearance than the homozygote.
6. A pink snapdragon is crossed to a white snapdragon. What is the probability of getting a red snap dragon?
a) 1
b) 1/2
c) 1/4
d) None
View Answer
Explanation: The color of snapdragon flower is controlled by incompletely dominant gene which in heterozygous condition expressed pink color. As the cross will only yield heterozygous and homozygous white allele condition, it is impossible to get a red flower which needs homozygous red condition.
7. Choose the odd one out.
a) MN blood group
b) ABO blood group
c) Color of chicken feather
d) Coat color of short horn cattle
View Answer
Explanation: This is because color of chicken feathering is an incompletely dominant trait while the remaining characters are codominant traits.
8. A child is born to a mother whose blood group is A and a father whose blood group is B. The child is of blood group A. According to this which of the following is true?
a) The mother has Bombay blood group
b) The child’s father is some other man
c) This is a normal case
d) The child has genotype IA/ IA
View Answer
Explanation: In such a case it is possible that the father was a heterozygote. So the case the recessive i allele to the child and the mother gave a dominant A allele. Thus the child has a blood genotype IA/ i and a phenotype of type A.
9. An M blood type daughter is born to a mother who has type M blood group and a father who has type N. Which of the following is true?
a) The father of the child is someone else
b) The mother of the child is someone else
c) This is a normal case
d) The child has genotype M/N
View Answer
Explanation: MN blood group shows codominance between two alleles M and N. Thus, the daughter to MM mother and NN father should have been MN. But as the daughter is MN, the father of the child is some other man.
10. If you cross two roan cows, what percentage of the progeny would you expect to be roan?
a) 10%
b) 25%
c) 50%
d) 75%
View Answer
Explanation: Roan coat colour in short horn cattle is a codominant trait n which case the roan cows are heterozygous for the coat colour gene. Thus according to monohybrid ratio ½ the progeny of the cross will be heterozygote, hence, roan.
11. What are the odds in favor that cross between a black and an Andalusian fowl will give 4 Andalusian fowls?
a) 1/2
b) 1/4
c) 1/8
d) 1/16
View Answer
Explanation: There is ½ probability that the progeny generated will be Andalusian. And the odds in favor that such event will occur 4 time is (1/2)4 =1/16.
12. Incomplete allele is the condition when some mutation in the wild type gene makes it lose its haplosufficiency.
a) True
b) False
View Answer
Explanation: It is thought that incomplete dominance is due to some mutation in the wild type gene such that the product so generated is no longer able to produce the complete phenotype of that allele, thus it is due to lose of haplosufficiency.
13. Among the progenies born from the mating of a white and an Andalusian fowl there are 5 white chickens. What is the expected total number of progeny?
a) 5
b) 10
c) 15
d) 25
View Answer
Explanation: In the following case half of the progeny so born must have been White while there is ½ probabilities that the rest were Andalusian. So overall the number of progeny is expected to be 10.
14. In case of codominance product is ___________________
a) Produced from both the alleles
b) Produced from one allele
c) Incompletely produced from both alleles
d) None are functional
View Answer
Explanation: In the case of codominance the product is produced from both the alleles and it is expressed in its fullness. No allele is dominant over the other.
15. If a person has M blood group which of the following is wrong?
a) He is a homozygote
b) His blood reacts to anti M antibody
c) His child’s blood would react to anti M antibody
d) His child will always have M blood type
View Answer
Explanation: In this case, the child will have either M blood type or MN depending on the other parent. But the rest of the options are true.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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