Principles of Genetics MCQs

1. In a dihybrid cross between two heterozygous individuals (AaBb x AaBb), the expected phenotypic ratio in the F2 generation is:
(A) 9:3:3:1
(B) 1:2:1
(C) 3:1
(D) 1:1:1:1

2. The phenomenon where one gene masks the expression of another gene is called:
(A) Epistasis
(B) Codominance
(C) Incomplete dominance
(D) Pleiotropy

3. In a test cross between an individual with genotype AaBb and an individual with genotype aabb, the offspring phenotype ratio would be:
(A) 1:1:1:1
(B) 1:1
(C) 9:3:3:1
(D) 1:2:1

4. Which of the following statements regarding X-linked inheritance is true?
(A) X-linked traits are inherited only through the maternal line
(B) Males have only one copy of the X chromosome, so they express X-linked recessive traits more often than females
(C) Females will always express an X-linked recessive trait if one of their X chromosomes carries the allele
(D) X-linked traits cannot be passed from father to son

5. In a case of incomplete dominance, the F1 generation of a cross between a red-flowered plant (RR) and a white-flowered plant (WW) would produce offspring with what phenotype?
(A) 100% red flowers
(B) 100% white flowers
(C) 100% pink flowers
(D) 1:2:1 red, pink, white flowers

6. The phenomenon in which a single gene influences multiple traits is called:
(A) Pleiotropy
(B) Codominance
(C) Polygenic inheritance
(D) Gene linkage

7. Which of the following best describes the concept of “genetic recombination” in eukaryotes?
(A) The random distribution of alleles during meiosis
(B) The process by which a dominant allele is expressed over a recessive allele
(C) The exchange of genetic material between homologous chromosomes during meiosis
(D) The independent assortment of chromosomes during mitosis

8. The Hardy-Weinberg equilibrium principle assumes all of the following EXCEPT:
(A) No mutation occurs
(B) No natural selection occurs
(C) The population is infinitely large
(D) All individuals must have the same genotype

9. Which of the following is an example of a genetic disorder caused by a trinucleotide repeat expansion?
(A) Cystic fibrosis
(B) Huntington’s disease
(C) Sickle cell anemia
(D) Down syndrome

10. Which of the following represents a situation where two different genes are located on the same chromosome and tend to be inherited together?
(A) Independent assortment
(B) Gene linkage
(C) Crossing over
(D) Epistasis

11. What is the expected phenotypic ratio in a monohybrid cross between two heterozygous individuals (Aa x Aa) for a dominant-recessive trait?
(A) 3:1
(B) 1:1
(C) 1:2:1
(D) 9:3:3:1

12. In a pedigree analysis, the presence of a disease in every generation suggests that the disease is likely:
(A) X-linked recessive
(B) Autosomal dominant
(C) X-linked dominant
(D) Autosomal recessive

13. In the case of codominance, what would be the expected phenotype of an F1 offspring from a cross between a red-flowered plant (RR) and a white-flowered plant (WW)?
(A) Pink flowers
(B) Red flowers
(C) White flowers
(D) Red and white striped flowers

14. Which of the following is true about the process of crossing over during meiosis?
(A) It occurs during metaphase I
(B) It results in the formation of recombinant chromosomes
(C) It only occurs in female gametes
(D) It ensures the production of identical gametes

15. A plant with genotype AaBbCc is crossed with another plant of the same genotype. The number of different gametes produced by each parent will be:
(A) 2
(B) 4
(C) 8
(D) 16