This set of Class 12 Biology Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance Principles – Pleiotropy”.
1. How is pleiotropy different from polygenic inheritance?
a) A single gene can exhibit multiple expressions
b) A single gene exhibits only a single expression
c) Two genes exhibit a single character
d) Multiple genes control a single character
Explanation: Pleiotropy is different from polygenic inheritance due to the fact that a single gene can exhibit multiple phenotypic expressions whereas in polygenic inheritance multiple genes control a single character.
2. What is the mechanism behind pleiotropy?
a) A single gene controls a single character
b) Effect of a gene on metabolic pathways
c) Effect of multiple genes on multiple pathways
d) Effect of multiple alleles on a biochemical pathway
Explanation: Pleiotropy is the phenomenon by which a single gene affects different metabolic pathways and these different metabolic pathways result in different phenotypes.
3. What is the full form of PKU?
a) Phenyl Ketonic Ubisch bodies
b) Para-keto ulna
d) Para-keto uremia
Explanation: PKU stands for phenylketonuria. This disease is caused by a pleiotropic gene where a single gene mutation takes place. The gene which codes for phenylalanine hydroxylase gets mutated.
4. Which of the following is not a symptom of phenylketonuria?
a) Mental retardation
b) Reduction in hair
c) White urine
d) Skin pigmentation
Explanation: White urine is not a symptom of Phenylketonuria. Phenylketonuria is a disease that is caused by a single gene mutation and is characterised by mental retardation, reduction in hair, black urine, and skin pigmentation.
5. Phenylketonuria is a sex-linked dominant trait.
Explanation: Phenylketonuria is not a sex-linked trait. Instead, it is an inborn error of metabolism which is also inherited as an autosomal recessive trait which means this disease will only occur in a progeny if it carries both the recessive genes from the parents.
6. Which of the following enzymes is not present in the patients of Phenylketonuria?
c) Phenylalanine hydroxylase
Explanation: The individual which is affected by phenylketonuria lacks a liver enzyme called phenylalanine hydroxylase which is responsible for converting phenylalanine, an amino acid into tyrosine, another amino acid.
7. Accumulation of which of the following in the brain leads to phenylketonuria?
a) Phenylpyruvic acid
b) Pyruvic acids
Explanation: Phenylketonuria is caused due to the accumulation of phenylalanine in the brain of the affected individuals. Phenylalanine and its derivative are also excreted through the urine because they are poorly absorbed by the kidneys.
8. Which of the following determines is responsible for determining the sex of the bacteria?
c) Core nucleus
Explanation: The fertility factor of the plasmid is responsible for determining sex in the bacteria. This theory or system is known as Non-Allosomic genetic sex determination.
9. Y chromosome plays a very significant role in the sex determination of Drosophila.
Explanation: The Y-chromosome does not play any role in the sex determination of Drosophila. According to C.B. Bridges, the ratio between the number of X-chromosome and the set of autosomes determines the sex of Drosophila.
10. What is the X/A ratio of super females of Drosophila?
Explanation: The X/A ratio is the ratio of the number of X-chromosomes and the set of autosomes. The X/A ratio of super females of Drosophila is 1.5. The X/A ratio of normal females, intersex, and super males of Drosophila is 1, 0.67, and 0.33 respectively.
11. How does Gynander differ from Gynandromorphs?
a) Gynander can only be a male
b) Gynander can only be a female
c) Gynander has patches of tissues of other sex on it
d) Gynander has one half body male and the other half as female
Explanation: A gynander differs from a gynandromorph in the fact that a gynander maybe a male or female with patches of tissues of other sex on it while gynandromorph is an individual with the one-half body as male and the other half as a female.
12. Which of the following shows gynandromorphism?
b) Silk moth
Explanation: Gynandromorphism is seen in Silk moth and Drosophila. It gets developed due to the accidental loss of the X-chromosome from a 2A + XX type of cell during the process of mitosis.
13. Which of the following does not show an environmental mechanism of sex determination?
Explanation: Grasshopper does not show and environmental mechanism of sex determination. It shows the chromosomal basis of sex determination. The environmental mechanism of sex determination is shown by Bonnelia, Crepidula, and Ophryotrocha.
14. Which of the following is not an example of sex-limited traits?
a) Milk glands in females
b) Short index finger in male
c) Beard in male
d) Deep male voice
Explanation: Short index finger in males is not an example of sex-limited traits. Sex limited traits are controlled by those genes which are found in both the sexes but can express themselves only in one sex.
15. Which of the following is a sex-influenced trait?
a) Antlers in male deer
b) Female or male musculature
c) Porcupine skin
d) Pattern baldness
Explanation: Pattern baldness is an example of a sex-influenced trait. These traits are controlled by those genes which are influenced by the sex of the bearer. These genes are known as autosomal genes.
16. Which of the following is not an example of a holandric trait?
a) Porcupine skin
c) Pattern baldness
d) Testes determining factor
Explanation: Pattern baldness is not an example of a holandric trait. Holandric traits are the Y-linked traits that are inherited from male parent to male progeny only. These include porcupine skin, Hypertrichosis, Testes determining factor, etc.
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