Genetic patterns of inheritance MCQs With Answer

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Genetic patterns of inheritance MCQs With Answer provide B. Pharm students a focused way to master inheritance concepts crucial for pharmacogenomics, drug response, and clinical genetics. This concise, keyword-rich introduction covers Mendelian laws, autosomal and sex-linked traits, penetrance, expressivity, epistasis, linkage mapping, Hardy–Weinberg equilibrium, and examples like ABO blood groups and CYP450 polymorphisms. Understanding these patterns helps pharmacists predict inheritance risks, interpret pedigrees, and apply genetic knowledge to individualized therapy. Practice with well-crafted multiple-choice questions strengthens reasoning for exams and real-world pharmacy decisions. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What principle describes separation of homologous alleles during gamete formation?

  • Law of Independent Assortment
  • Law of Segregation
  • Law of Dominance
  • Law of Uniformity

Correct Answer: Law of Segregation

Q2. Which law explains how alleles of different genes assort independently during gamete formation?

  • Law of Segregation
  • Law of Dominance
  • Law of Independent Assortment
  • Law of Recombination

Correct Answer: Law of Independent Assortment

Q3. In a monohybrid cross of two heterozygous parents (Aa × Aa), what is the expected genotypic ratio?

  • 3:1
  • 1:1
  • 1:2:1
  • 9:3:3:1

Correct Answer: 1:2:1

Q4. In the same monohybrid cross (Aa × Aa), what is the expected phenotypic ratio when A is completely dominant?

  • 1:2:1
  • 3:1
  • 9:3:3:1
  • 2:1

Correct Answer: 3:1

Q5. Which inheritance pattern shows heterozygotes with intermediate phenotype between two homozygotes?

  • Codominance
  • Incomplete dominance
  • Epistasis
  • Pleiotropy

Correct Answer: Incomplete dominance

Q6. Which pattern displays both alleles expressed equally in a heterozygote (e.g., AB blood type)?

  • Incomplete dominance
  • Codominance
  • Complete dominance
  • Recessive epistasis

Correct Answer: Codominance

Q7. Which term describes the proportion of individuals with a genotype who exhibit the associated phenotype?

  • Expressivity
  • Penetrance
  • Pleiotropy
  • Epistasis

Correct Answer: Penetrance

Q8. Which term refers to variation in phenotype severity among individuals with the same genotype?

  • Penetrance
  • Expressivity
  • Heterozygosity
  • Linkage disequilibrium

Correct Answer: Expressivity

Q9. What is pleiotropy?

  • Multiple genes affecting one trait
  • One gene influencing multiple phenotypic traits
  • Genes located close together on the same chromosome
  • Alleles showing incomplete dominance

Correct Answer: One gene influencing multiple phenotypic traits

Q10. What is epistasis?

  • Interaction where alleles of one gene mask effects of another gene
  • Equal expression of both alleles in a heterozygote
  • Inheritance of mitochondrial genes from mother
  • Random mutation during gametogenesis

Correct Answer: Interaction where alleles of one gene mask effects of another gene

Q11. Which cross typically produces a 9:3:3:1 phenotypic ratio in F2 offspring?

  • Monohybrid cross of two heterozygotes
  • Dihybrid cross of two heterozygotes with independent assortment
  • Testcross of a heterozygote with a homozygous recessive
  • Backcross of homozygotes

Correct Answer: Dihybrid cross of two heterozygotes with independent assortment

Q12. Which inheritance shows males more frequently affected than females, often skipping generations and transmitted by carrier females?

  • Autosomal dominant
  • Autosomal recessive
  • X-linked recessive
  • X-linked dominant

Correct Answer: X-linked recessive

Q13. Mitochondrial (maternal) inheritance is characterized by which feature?

  • Transmission only through affected fathers
  • Transmission through both parents equally
  • Transmission only through mothers to all offspring
  • Male-to-male transmission only

Correct Answer: Transmission only through mothers to all offspring

Q14. Which pedigree feature suggests autosomal dominant inheritance?

  • Multiple affected siblings with unaffected parents
  • Trait appears in every generation and both sexes affected
  • Only males affected and transmitted by females
  • Only offspring of consanguineous unions affected

Correct Answer: Trait appears in every generation and both sexes affected

Q15. Which pedigree pattern suggests autosomal recessive inheritance?

  • Trait present in every generation
  • Two unaffected parents having an affected child
  • Males predominantly affected and transmitted by females
  • Father to all daughters transmission

Correct Answer: Two unaffected parents having an affected child

Q16. What is the purpose of a testcross?

  • To determine recombination frequency between genes
  • To identify whether an individual with dominant phenotype is homozygous or heterozygous
  • To measure penetrance in a population
  • To calculate allele frequencies under Hardy–Weinberg

Correct Answer: To identify whether an individual with dominant phenotype is homozygous or heterozygous

Q17. What does a recombination frequency of 50% between two loci indicate?

  • Genes are tightly linked on the same chromosome
  • Genes are very close with no crossing over
  • Genes assort independently or are far apart on the same chromosome
  • One gene is epistatic to the other

Correct Answer: Genes assort independently or are far apart on the same chromosome

Q18. One centimorgan (cM) approximates what recombination frequency?

  • 0.01% recombination
  • 1% recombination
  • 10% recombination
  • 50% recombination

Correct Answer: 1% recombination

Q19. Hardy–Weinberg equilibrium assumes which of the following?

  • Non-random mating and small population size
  • No mutation, no migration, no selection, large population, random mating
  • Strong selection and high mutation rate
  • Linkage disequilibrium and assortative mating

Correct Answer: No mutation, no migration, no selection, large population, random mating

Q20. In Hardy–Weinberg, if allele p = 0.7 and q = 0.3, what is expected frequency of heterozygotes?

  • p^2 = 0.49
  • q^2 = 0.09
  • 2pq = 0.42
  • p + q = 1.0

Correct Answer: 2pq = 0.42

Q21. What is the expected phenotype of an individual heterozygous for an autosomal dominant lethal allele where homozygotes die before birth?

  • Homozygote viable with severe phenotype
  • Heterozygote typically affected; homozygotes absent (reduced proportion of affected offspring)
  • Homozygotes more common than heterozygotes
  • No phenotypic effect in heterozygotes

Correct Answer: Heterozygote typically affected; homozygotes absent (reduced proportion of affected offspring)

Q22. What does reduced penetrance mean?

  • All individuals with genotype show identical phenotype
  • Some individuals with the disease genotype do not express the phenotype
  • Phenotype severity varies but all express it
  • Trait is only expressed in homozygotes

Correct Answer: Some individuals with the disease genotype do not express the phenotype

Q23. Which concept explains variable phenotype due to environmental influences and multiple genes?

  • Monogenic inheritance
  • Polygenic and multifactorial inheritance
  • Simple recessive inheritance
  • Mitochondrial inheritance

Correct Answer: Polygenic and multifactorial inheritance

Q24. Which genetic phenomenon leads to earlier onset or increased severity in successive generations (e.g., Huntington disease)?

  • Genomic imprinting
  • Anticipation due to trinucleotide repeat expansion
  • Incomplete dominance
  • Codominance

Correct Answer: Anticipation due to trinucleotide repeat expansion

Q25. What is genomic imprinting?

  • Equal expression of maternal and paternal alleles
  • Allele expression depends on parent of origin due to epigenetic marks
  • Mutation rate higher in imprinted genes
  • Only mitochondrial genes are expressed

Correct Answer: Allele expression depends on parent of origin due to epigenetic marks

Q26. Which test uses observed vs expected ratios to assess fit of genetic cross data?

  • Chi-square test
  • ANOVA
  • t-test
  • Fisher’s exact test only

Correct Answer: Chi-square test

Q27. What is a testcross used to detect?

  • Whether two genes are linked
  • Whether an individual of dominant phenotype is homozygous or heterozygous
  • Population allele frequencies
  • Chromosomal aneuploidy

Correct Answer: Whether an individual of dominant phenotype is homozygous or heterozygous

Q28. Which blood group system demonstrates multiple alleles and codominance?

  • Rh blood group
  • ABO blood group
  • Kell blood group
  • Duffy blood group

Correct Answer: ABO blood group

Q29. The O blood group genotype is homozygous for which allele type?

  • IAIO
  • IBIO
  • IOIO
  • IAIB

Correct Answer: IOIO

Q30. Rh-negative phenotype is usually due to absence of which antigen?

  • A antigen
  • B antigen
  • Rh (D) antigen
  • H antigen

Correct Answer: Rh (D) antigen

Q31. Which inheritance pattern is characteristic of most CYP450 polymorphisms affecting drug metabolism?

  • X-linked recessive inheritance
  • Mitochondrial inheritance
  • Autosomal codominant or multiple-allele inheritance creating variable phenotypes
  • Y-linked inheritance

Correct Answer: Autosomal codominant or multiple-allele inheritance creating variable phenotypes

Q32. A patient is homozygous for a loss-of-function CYP2D6 allele yielding poor metabolizer phenotype; this is an example of:

  • Dominant negative effect
  • Null allele producing recessive-like metabolic phenotype
  • X-linked overexpression
  • Mitochondrial dysfunction

Correct Answer: Null allele producing recessive-like metabolic phenotype

Q33. Heterozygote advantage, such as sickle cell trait protecting against malaria, best illustrates which concept?

  • Directional selection against heterozygotes
  • Balancing selection maintaining polymorphism
  • Genetic drift eliminating alleles
  • Founder effect

Correct Answer: Balancing selection maintaining polymorphism

Q34. Consanguinity increases risk of which type of genetic disorders?

  • Autosomal dominant disorders only
  • Sex-linked dominant disorders
  • Autosomal recessive disorders due to increased homozygosity
  • Mitochondrial disorders

Correct Answer: Autosomal recessive disorders due to increased homozygosity

Q35. What is genetic linkage?

  • Genes located on different chromosomes that assort independently
  • Genes close together on same chromosome that tend to be inherited together
  • Random association of alleles in a population
  • Expression of both alleles equally

Correct Answer: Genes close together on same chromosome that tend to be inherited together

Q36. A recombination frequency of 5% corresponds to about how many map units between two genes?

  • 0.05 cM
  • 5 cM
  • 50 cM
  • 500 cM

Correct Answer: 5 cM

Q37. Somatic mosaicism refers to which situation?

  • Individuals have two or more genetically distinct cell lines derived from same zygote
  • All cells in body have identical genotype
  • Only germ cells carry a mutation
  • Inheritance strictly follows Mendel’s laws

Correct Answer: Individuals have two or more genetically distinct cell lines derived from same zygote

Q38. A de novo mutation is best defined as:

  • A mutation inherited from grandparents only
  • A mutation present in reproductive cells that arises newly in the child and is not present in parents
  • A mutation that reverts to wild type in offspring
  • A polymorphism present in population at >1% frequency

Correct Answer: A mutation present in reproductive cells that arises newly in the child and is not present in parents

Q39. Imprinting disorders like Prader–Willi and Angelman syndromes result from:

  • Different phenotypes depending on whether maternal or paternal allele is deleted or silenced
  • Loss of function in mitochondrial DNA only
  • Codominant inheritance of two alleles
  • Autosomal dominant gain-of-function mutations only

Correct Answer: Different phenotypes depending on whether maternal or paternal allele is deleted or silenced

Q40. Which analysis helps determine whether observed F2 ratios deviate significantly from expected Mendelian ratios?

  • Hardy–Weinberg calculation
  • Chi-square goodness-of-fit test
  • Linkage mapping only
  • BLAST sequence alignment

Correct Answer: Chi-square goodness-of-fit test

Q41. In X-linked dominant inheritance, what is a key pedigree feature?

  • Only males affected and transmitted by fathers
  • Both sexes affected but affected fathers transmit to all daughters and no sons
  • Trait always skips generations
  • Only females affected

Correct Answer: Both sexes affected but affected fathers transmit to all daughters and no sons

Q42. Lyonization refers to which process?

  • Random inactivation of one X chromosome in females
  • Duplication of Y chromosome in males
  • Crossing over between autosomes
  • Mitochondrial DNA replication

Correct Answer: Random inactivation of one X chromosome in females

Q43. Which technique is commonly used to map recombination and establish genetic distances between loci?

  • Pedigree analysis with recombination frequency calculation
  • Western blotting
  • ELISA for protein quantification
  • Mass spectrometry of metabolites

Correct Answer: Pedigree analysis with recombination frequency calculation

Q44. A patient with two carrier parents for an autosomal recessive disease has what risk of being affected?

  • 0% risk
  • 25% risk
  • 50% risk
  • 100% risk

Correct Answer: 25% risk

Q45. If an autosomal recessive disorder is rare, most affected individuals are born to parents who are:

  • Both carriers
  • One affected and one unaffected
  • Both affected
  • Neither a carrier

Correct Answer: Both carriers

Q46. Which population-genetic process can cause large shifts in allele frequency in small populations and is random?

  • Natural selection
  • Genetic drift
  • Mutation-selection balance
  • Gene flow

Correct Answer: Genetic drift

Q47. Founder effect is best described as:

  • Loss of genetic variation when a new population is established by a small number of individuals
  • Immediate increase in mutation rate across population
  • Balancing selection maintaining heterozygotes
  • Random mating ensuring HWE

Correct Answer: Loss of genetic variation when a new population is established by a small number of individuals

Q48. What is the Hardy–Weinberg expected frequency of homozygous dominant genotype in terms of p?

  • p
  • q
  • p^2
  • 2pq

Correct Answer: p^2

Q49. In pedigree analysis, an affected child from two unaffected parents most likely indicates which inheritance when trait is rare?

  • Autosomal dominant
  • Autosomal recessive
  • X-linked dominant
  • Y-linked

Correct Answer: Autosomal recessive

Q50. For pharmacogenetics, why is understanding inheritance patterns (e.g., CYP polymorphisms) important for a B. Pharm student?

  • It is only of theoretical interest with no clinical relevance
  • It helps predict drug response, guide dosing, and reduce adverse drug reactions through personalized therapy
  • It replaces the need for clinical trials
  • It determines drug chemical stability

Correct Answer: It helps predict drug response, guide dosing, and reduce adverse drug reactions through personalized therapy

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