Genetics: Principles of Inheritance and Variation MCQ Test

21. Which characteristic is true for polygenic traits?

• They are controlled by a single gene.
• Their phenotype reflects the additive contribution of each allele.
• They show distinct alternate forms, like tall or dwarf.
• Environmental factors have no influence on their expression.

22. In human sex determination, what determines the sex of the child?

• The mother's ovum, as it carries either an X or a Y chromosome.
• The father's sperm, as it carries either an X or a Y chromosome.
• The number of autosomes present in the zygote.
• Environmental factors during gestation.

23. In the haplodiploid sex-determination system of honey bees:

• Males are diploid and females are haploid.
• Fertilized eggs develop into males.
• Unfertilised eggs develop into males through parthenogenesis.
• Males have a father but no sons.

24. A change in a single base pair of DNA is known as a:

• Chromosomal aberration
• Frame-shift mutation
• Point mutation
• Deletion

25. Which of the following is an example of an X-linked recessive Mendelian disorder characterized by non-stop bleeding from a simple cut?

• Sickle-cell anaemia
• Phenylketonuria
• Thalassemia
• Haemophilia

26. The defect in sickle-cell anaemia is primarily caused by:

• A chromosomal deletion.
• An extra copy of chromosome 21.
• Substitution of Glutamic acid by Valine in the beta globin chain due to a single base substitution.
• Reduced synthesis of globin chains.

27. How does Thalassemia primarily differ from Sickle-cell anaemia?

• Thalassemia is a qualitative problem of incorrectly functioning globin, while sickle-cell is quantitative.
• Thalassemia is an autosome-linked dominant trait, while sickle-cell is recessive.
• Thalassemia is a quantitative problem of synthesising too few globin molecules, while sickle-cell is a qualitative problem.
• Thalassemia only affects alpha globin chains, while sickle-cell affects beta globin chains.

28. Down's Syndrome is a chromosomal disorder resulting from:

• Absence of an X chromosome.
• An additional copy of chromosome 21.
• Presence of an additional X-chromosome (XXY).
• Loss of a segment of DNA.

29. An individual with Klinefelter's Syndrome typically has a karyotype of:

• 45, X0
• 47, XXY
• 47, +21
• 46, XY

30. Which of the following characteristics is associated with Turner's Syndrome?

• Overall masculine development with gynaecomastia.
• Short stature, furrowed tongue, mental retardation.
• Sterile females with rudimentary ovaries and lack of secondary sexual characters.
• Normal male characteristics with impaired clotting.

31. A normal human cell contains how many pairs of chromosomes?

• 22
• 23
• 46
• 47

32. The phenomenon where an organism has an increase in a whole set of chromosomes, often seen in plants due to failure of cytokinesis after telophase, is known as:

• Aneuploidy
• Trisomy
• Monosomy
• Polyploidy

33. Colour blindness occurs in about 8% of males but only about 0.4% of females. This difference is primarily because:

• Males are more exposed to environmental mutagens.
• The genes for colour blindness are on the Y chromosome.
• The genes for colour blindness are on the X chromosome, and males have only one X.
• Females have a stronger immune system against genetic defects.

34. In the haplodiploid sex-determination system, males produce sperms by:

• Meiosis
• Mitosis
• Fertilization
• Parthenogenesis

35. Humans knew about variation and exploited it through selective breeding as early as:

• Mid-nineteenth century
• 1900
• 8000-1000 B.C.
• 1953

36. A heterozygous individual (e.g., Tt for tall height) produces gametes containing the alleles T and t in what proportion?

• 1:3
• 3:1
• 1:1
• 2:1

37. Which of Mendel's observations refuted the idea of 'blending inheritance'?

• The 9:3:3:1 ratio in dihybrid crosses.
• The fact that all F1 progeny in a monohybrid cross resembled one parent.
• The reappearance of the recessive trait in the F2 generation without any intermediate forms.
• The Law of Independent Assortment.

38. The ABO blood grouping system in humans is an example of multiple alleles because:

• It involves two genes.
• It shows incomplete dominance.
• There are more than two alleles governing the same character in the population.
• Both IA and IB are completely dominant over i.

39. When a single gene product produces more than one effect, such a gene is called a:

• Polygenic gene
• Linked gene
• Pleiotropic gene
• Recessive gene

40. In many birds, the sex determination mechanism is of the ZW type. Which statement is correct regarding their sex chromosomes?

• Males are ZW and females are ZZ.
• Males are ZZ and females are ZW.
• Both males and females are ZW.
• Both males and females are ZZ.