MDCAT Biology: Inheritance MCQs

Practice MDCAT Biology Inheritance MCQs with explanations — PMC, ETEA, NUMS entry test preparation.

MDCAT Biology: Inheritance MCQs

  1. Question 1

    Q1. If a couple has a child with cystic fibrosis, an autosomal recessive disorder, what is the probability that their next child will be a carrier?

    • A) 1/2
    • B) 1/3
    • C) 2/3
    • D) 3/4

    Answer: 2/3

    Explanation: Both parents must be carriers, so 2/3 chance the next child is a carrier.

  2. Question 2

    Q2. What is the purpose of the leading strand during DNA replication?

    • A) To synthesize the lagging strand
    • B) To synthesize the leading strand
    • C) To unwind the double helix
    • D) To proofread the new DNA

    Answer: To synthesize the leading strand

    Explanation: Leading strand is synthesized continuously in the 5' to 3' direction.

  3. Question 3

    Q3. A couple has a child with a genetic disorder caused by a dominant allele. What is the probability that the next child will have the disorder?

    • A) 1/2
    • B) 1/3
    • C) 1/4
    • D) 2/3

    Answer: 1/2

    Explanation: Each child has a 50% chance of inheriting the dominant allele.

  4. Question 4

    Q4. A genetic test reveals that a couple's child has a chromosomal abnormality. What is the term for the presence of an extra copy of a chromosome?

    • A) Aneuploidy
    • B) Polyploidy
    • C) Triploidy
    • D) Trisomy

    Answer: Trisomy

    Explanation: Trisomy refers to the presence of an extra chromosome, such as in Down syndrome.

  5. Question 5

    Q5. What is the term for the movement of molecules from an area of higher concentration to an area of lower concentration?

    • A) Osmosis
    • B) Diffusion
    • C) Active transport
    • D) Passive transport

    Answer: Diffusion

    Explanation: Diffusion is the movement of molecules down a concentration gradient.

  6. Question 6

    Q6. A genetic disorder caused by a mutation in the CFTR gene is

    • A) Sickle cell anemia
    • B) Cystic fibrosis
    • C) Tay-Sachs disease
    • D) Phenylketonuria

    Answer: Cystic fibrosis

    Explanation: Cystic fibrosis is caused by a mutation in the CFTR gene.

  7. Question 7

    Q7. In a population, what is the term for the total number of alleles for a particular gene?

    • A) Gene pool
    • B) Genotype
    • C) Phenotype
    • D) Allele frequency

    Answer: Gene pool

    Explanation: Gene pool refers to the total number of alleles in a population.

  8. Question 8

    Q8. A couple has a child with a genetic disorder caused by a recessive allele. If both parents are carriers, what is the probability that their next child will have the disorder?

    • A) 1/2
    • B) 1/3
    • C) 1/4
    • D) 2/3

    Answer: 1/4

    Explanation: Each child has a 25% chance of inheriting two recessive alleles.

  9. Question 9

    Q9. In a population, what is the term for the frequency of a particular allele?

    • A) Genotype frequency
    • B) Phenotype frequency
    • C) Allele frequency
    • D) Gene frequency

    Answer: Allele frequency

    Explanation: Allele frequency is the proportion of a particular allele in a population.

  10. Question 10

    Q10. What is the term for the phenomenon where a dominant allele has a greater effect on the phenotype than a recessive allele?

    • A) Dominance
    • B) Recessive
    • C) Incomplete dominance
    • D) Codominance

    Answer: Dominance

    Explanation: Dominance refers to the greater effect of a dominant allele.

  11. Question 11

    Q11. A genetic disorder caused by a frameshift mutation is

    • A) Sickle cell anemia
    • B) Cystic fibrosis
    • C) Tay-Sachs disease
    • D) Phenylketonuria

    Answer: Tay-Sachs disease

    Explanation: Tay-Sachs disease is caused by a frameshift mutation in the HEXA gene.

  12. Question 12

    Q12. A couple has a child with cystic fibrosis, an autosomal recessive disorder. What is the probability that their next child will be a carrier?

    • A) 1/2
    • B) 1/3
    • C) 1/4
    • D) 2/3

    Answer: 2/3

    Explanation: Each child has a 2/3 chance of being a carrier or unaffected.

  13. Question 13

    Q13. In a population, the frequency of the allele for blue eyes is 0.2. What is the frequency of the genotype for blue eyes, assuming the population is in Hardy-Weinberg equilibrium?

    • A) 0.04
    • B) 0.16
    • C) 0.2
    • D) 0.4

    Answer: 0.04

    Explanation: The frequency of the genotype is the square of the allele frequency.

  14. Question 14

    Q14. A plant with the genotype 'Rr' is crossed with a plant of genotype 'rr'. What is the probability that the offspring will have red flowers?

    • A) 0%
    • B) 25%
    • C) 50%
    • D) 100%

    Answer: 50%

    Explanation: The 'R' allele is dominant, so all offspring will have red flowers.

  15. Question 15

    Q15. A couple has a child with an autosomal dominant disorder. What is the probability that their next child will also be affected?

    • A) 25%
    • B) 50%
    • C) 75%
    • D) 100%

    Answer: 50%

    Explanation: Each child has a 50% chance of inheriting the dominant allele.

  16. Question 16

    Q16. In a population, the frequency of the allele for a certain trait is 0.4. What is the frequency of the genotype for the trait, assuming the population is in Hardy-Weinberg equilibrium?

    • A) 0.16
    • B) 0.24
    • C) 0.36
    • D) 0.64

    Answer: 0.36

    Explanation: The frequency of the genotype is the square of the allele frequency.

  17. Question 17

    Q17. In a population, the frequency of the allele for a certain trait is 0.6. What is the frequency of the genotype for the trait, assuming the population is in Hardy-Weinberg equilibrium?

    • A) 0.24
    • B) 0.36
    • C) 0.64
    • D) 0.84

    Answer: 0.64

    Explanation: The frequency of the genotype is the square of the allele frequency.

  18. Question 18

    Q18. In a pedigree chart, if two parents are carriers of a recessive disorder, what is the probability of their offspring being affected?

    • A) 25%
    • B) 50%
    • C) 33%
    • D) 66%

    Answer: 25%

    Explanation: Autosomal recessive inheritance pattern, 25% chance of offspring being affected

  19. Question 19

    Q19. What is the term for the physical appearance of a trait, which can be influenced by multiple genes?

    • A) Genotype
    • B) Phenotype
    • C) Dominance
    • D) Incomplete dominance

    Answer: Phenotype

    Explanation: Phenotype refers to physical appearance, genotype refers to genetic makeup

  20. Question 20

    Q20. In a dihybrid cross, what is the expected ratio of offspring with the dominant phenotype?

    • A) 3:1
    • B) 9:3:3:1
    • C) 1:1
    • D) 2:1

    Answer: 9:3:3:1

    Explanation: Dihybrid cross results in 9:3:3:1 ratio, 9 parts dominant phenotype

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