MCQs / Biology / A Level Biology: Inheritance

A Level Biology: Inheritance MCQs — Biology

35 multiple-choice questions on A Level Biology: Inheritance from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. A structural gene codes for

  1. a protein that regulates other genes
  2. a protein with a structural or metabolic function
  3. tRNA only
  4. a promoter

Answer: B) a protein with a structural or metabolic function

Explanation: Definition. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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2. Albinism results from a mutation in the TYR gene which codes for

  1. huntingtin
  2. β-globin
  3. tyrosinase
  4. factor VIII

Answer: C) tyrosinase

Explanation: Tyrosinase makes melanin. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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3. Haemophilia is more common in males because

  1. it is on the Y chromosome
  2. males have two X chromosomes
  3. the allele is dominant
  4. males have only one X chromosome

Answer: D) males have only one X chromosome

Explanation: X-linked recessive conditions show in hemizygous males. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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4. Sickle cell anaemia is caused by a mutation in the

  1. HBB gene
  2. TYR gene
  3. F8 gene
  4. HTT gene

Answer: A) HBB gene

Explanation: HBB codes for β-globin. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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5. Homologous chromosomes are

  1. a pair with the same genes at the same loci, one from each parent
  2. two identical sister chromatids
  3. chromosomes from different species
  4. the X and Y only

Answer: A) a pair with the same genes at the same loci, one from each parent

Explanation: Definition of homologues. AS & A Level Biology · Topic 16 Inheritance · 16.1 Passage of information from parents to offspring

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6. RNA polymerase binds to the

  1. operator
  2. promoter
  3. lacZ gene
  4. repressor

Answer: B) promoter

Explanation: The promoter is the binding site. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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7. DELLA proteins inhibit germination by

  1. binding to transcription factors and stopping them promoting transcription
  2. breaking down gibberellin
  3. binding to the repressor
  4. making amylase

Answer: A) binding to transcription factors and stopping them promoting transcription

Explanation: DELLA proteins are repressors. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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8. The F8 gene codes for

  1. tyrosinase
  2. factor VIII, a blood clotting protein
  3. haemoglobin
  4. insulin

Answer: B) factor VIII, a blood clotting protein

Explanation: F8 → factor VIII. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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9. Dwarf pea plants (lele) are short because

  1. the le allele codes for a non-functional enzyme in gibberellin synthesis
  2. they lack chlorophyll
  3. they make too much gibberellin
  4. the Le allele is recessive

Answer: A) the le allele codes for a non-functional enzyme in gibberellin synthesis

Explanation: Little active gibberellin, less elongation. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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10. When lactose is present, it

  1. binds to the repressor, changing its shape so it cannot bind the operator
  2. binds to the promoter
  3. binds to RNA polymerase
  4. destroys the operator

Answer: A) binds to the repressor, changing its shape so it cannot bind the operator

Explanation: Inducer inactivates repressor. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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11. Transcription factors

  1. are enzymes that hydrolyse lactose
  2. bind to DNA and increase or decrease transcription
  3. translate mRNA
  4. are structural proteins

Answer: B) bind to DNA and increase or decrease transcription

Explanation: They regulate gene expression in eukaryotes. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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12. β-galactosidase is an example of

  1. a regulatory protein
  2. a transcription factor
  3. a repressible enzyme
  4. an inducible enzyme

Answer: D) an inducible enzyme

Explanation: Made only when lactose is present. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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13. Crossing over takes place during

  1. anaphase I
  2. prophase I
  3. telophase II
  4. metaphase II

Answer: B) prophase I

Explanation: Chiasmata form in prophase I. AS & A Level Biology · Topic 16 Inheritance · 16.1 Passage of information from parents to offspring

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14. Epistasis is when

  1. genes are on the same chromosome
  2. one gene affects the expression of another gene at a different locus
  3. a gene is on the X chromosome
  4. two alleles are both expressed

Answer: B) one gene affects the expression of another gene at a different locus

Explanation: Gene interaction. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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15. Huntington's disease is caused by

  1. an X-linked recessive allele
  2. a recessive allele of HBB
  3. a mutation in TYR
  4. a dominant allele of HTT with extra CAG repeats

Answer: D) a dominant allele of HTT with extra CAG repeats

Explanation: Huntingtin with extra glutamines. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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16. A test cross involves crossing an organism with

  1. a homozygous dominant individual
  2. a heterozygous individual
  3. itself
  4. a homozygous recessive individual

Answer: D) a homozygous recessive individual

Explanation: Recessive tester reveals genotype. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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17. The regulatory gene in the lac operon codes for

  1. the repressor protein
  2. β-galactosidase
  3. lactose permease
  4. RNA polymerase

Answer: A) the repressor protein

Explanation: lacI codes for the repressor. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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18. The number of cells produced by one meiotic division is

  1. two diploid cells
  2. two haploid cells
  3. four diploid cells
  4. four haploid cells

Answer: D) four haploid cells

Explanation: Meiosis I and II give four cells. AS & A Level Biology · Topic 16 Inheritance · 16.1 Passage of information from parents to offspring

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19. Calculate χ² for observed 30 and 10 against expected 30 and 10.

  1. 40
  2. 1
  3. 0
  4. 10

Answer: C) 0

Explanation: No difference gives χ² = 0. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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20. Random fertilisation increases variation because

  1. any male gamete can fuse with any female gamete
  2. crossing over occurs during fertilisation
  3. gametes are identical
  4. it halves chromosomes

Answer: A) any male gamete can fuse with any female gamete

Explanation: More combinations. AS & A Level Biology · Topic 16 Inheritance · 16.1 Passage of information from parents to offspring

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21. In a chi-squared test, if χ² is less than the critical value at p = 0.05,

  1. the results are significant
  2. the experiment failed
  3. the hypothesis must be rejected
  4. the difference between observed and expected is due to chance

Answer: D) the difference between observed and expected is due to chance

Explanation: Not significant. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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22. In anaphase I of meiosis,

  1. nuclear envelopes re-form
  2. chromosomes line up singly
  3. homologous chromosomes separate
  4. sister chromatids separate

Answer: C) homologous chromosomes separate

Explanation: Homologues go to opposite poles in anaphase I. AS & A Level Biology · Topic 16 Inheritance · 16.1 Passage of information from parents to offspring

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23. In the lac operon, when lactose is absent,

  1. β-galactosidase is made
  2. RNA polymerase transcribes lacZ
  3. lactose binds the repressor
  4. the repressor binds to the operator and blocks transcription

Answer: D) the repressor binds to the operator and blocks transcription

Explanation: No lactose = genes off. AS & A Level Biology · Topic 16 Inheritance · 16.3 Gene control

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24. A woman who is a carrier of haemophilia (XᴴXʰ) has children with an unaffected man. The probability that a son is affected is

  1. 0.5
  2. 1
  3. 0
  4. 0.25

Answer: A) 0.5

Explanation: Sons receive X from the mother: half get Xʰ. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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25. When two genes are linked on the same autosome, a dihybrid test cross produces

  1. 9 : 3 : 3 : 1
  2. mostly parental phenotypes with few recombinants
  3. only recombinants
  4. exactly 1 : 1 : 1 : 1

Answer: B) mostly parental phenotypes with few recombinants

Explanation: Linked genes stay together unless crossed over. AS & A Level Biology · Topic 16 Inheritance · 16.2 The roles of genes in determining the phenotype

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