Principles of Inheritance and Variation Assertion Reason Based Questions

The following questions consist of two statements, one labelled as Assertion (A) and the other labelled the Reason ®. Examine these two statements carefully and select the most appropriate answer codes.

(a)Assertion and reason both are correct and reason is the correct explanation of Assertion.
(b)Assertion and reason both are correct and reason is not the correct explanation of Assertion.
(c)Assertion is correct but reason is wrong.
(d)Both Assertion and Reason are false.

1. Assertion: In a monohybrid cross, F1 generations indicate dominant character.
   Reason: Dominance occurs only in heterozygous state.
2. Assertion: Pure lines are called true breed.
   Reason: True breeds are used for cross breeding.
3. Assertion: Co- dominant alleles lack dominant recessive relationship.
   Reason: Co-dominant alleles show incomplete dominance.
4. Assertion: The principle of segregation given by Mendel is the principal of purity of gametes.
   Reason: Gametes are pure for a character.
5. Assertion: Complementary genes are non-allelic genes.
   Reason: Complementary genes interact to produce a completely new trait.
6. Assertion: Quantitative inheritance is called polygenic inheritance.
   Reason: Several genes control the expression of a trait.
7. Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combination is much higher than non-parental type.
   Reason: Higher parental gene combinations can be attributed to crossing over between two genes.
8. Assertion: Accumulation of phenylalanine in the brain results in mental retardation in phenylketonuria.
   Reason: The affected person lacks phenylalanine which is therefore not converted to tyrosine.
9. Assertion: In garden pea, the gene which controls the flower colour also control the colour of the seed coat and presence of red spots in the leaf axils.
   Reason: A pleiotropic gene influences more than one trait.
10. Assertion: Mendel’s work was not accepted by the scientific community from 1865 to 1900.
    Reason: It did not fit into the community’s conception of the relationship of heredity to other sciences.
11. Assertion: The cytoplasmic genes do not show Mendelian inheritance.
    Reason: In this reciprocal crosses yield different results.
12. Assertion: Tr × tt is an example of a test cross.
    Reason: Test cross distinguishes a homozygous dominant from a heterozygous genotype.
13. Assertion: Drosophila is extensively used in genetical research.
    Reason: It possesses very large polytene chromosome.
14. Assertion: Deletion of a nitrogenous base pair in DNA causes frameshift mutation.
    Reason: The replacement of a purine by a pyrimidine is known as transition.
15. Assertion: Mutation can cause a change in protein structure.
    Reason: Gene mutations alter the DNA sequences of a gene.
16. Assertion: Analysis of the inheritance of genes in human must rely on Pedigree analysis.
    Reason: Controlled mating cannot be made in humans.
17. Assertion: The presence of Y-chromosomes specifies maleness in human beings.
    Reason: The X-chromosome carry a gene SRY which directs the female sex differentiation.
18. Assertion: Person suffering from haemophilia fail to produce blood clotting factor VIII.
    Reason: Prothrombin producing platelets in such persons are found in very low concentration.
19. Assertion: A Turner syndrome individual would be expected to have no Barr body.
    Reason: Her sex chromosome constitution is XO.
20. Assertion: Huntington’s disease is a human disease inherited as a Medelian autosomal dominant.
    Reason: This disease is more common in males than in females.
21. Assertion: The ABO blood series provides a good example of co-dominance.
    Reason: In this the heterozygote exhibits the phenotypes of both homozygotes.
22. Assertion: Deletion is a chromosomal mutation involving the loss of segment of a chromosome.
    Reason: Down syndrome results from the deletion of a part of human chromosome 21.
23. Assertion: For a particular character in an individual, each gamete gets only one allele.
    Reason: Chromatids of a chromosome split and move towards opposite poles during anaphase of mitosis.
24. Assertion: In birds, the chromosome composition of the egg determine the sex.
    Reason: Female birds are heterogametic.
25. Assertion: Haplodiploidy occurs in some insects.
    Reason: Male insects develop parthenogenetically, while females grow from fertilized egg.

Answer Sheet

1. A
2. B
3. C
4. A
5. B
6. A
7. C
8. C
9. A
10. A
11. A
12. B
13. A
14. C
15. A
16. A
17. C
18. C
19. A
20. C
21. A
22. C
23. B
24. B
25. A