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Quiz Chapter 12: Variation

10 questions · Form 5 Biology Bab 12: Variation

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. What is the total chromosome number and sex chromosome composition in an individual with Turner syndrome?

  1. 47, XXY
  2. 45, XO
  3. 47, Trisomy 21
  4. 46, XX
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Answer: B

Turner syndrome females have 45 total chromosomes with a single X chromosome (44 autosomes + XO).

2. What is the key difference between a gene mutation and a chromosomal mutation?

  1. Gene mutations affect whole chromosomes; chromosomal mutations affect single bases
  2. Gene mutations alter the nucleotide sequence of a specific gene; chromosomal mutations alter structure or total number of chromosomes
  3. Gene mutations are inherited; chromosomal mutations are never inherited
  4. Gene mutations only occur in plants; chromosomal mutations only occur in animals
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Answer: B

Gene mutations affect nucleotide sequences within single genes, whereas chromosomal mutations involve structural or numerical changes in whole chromosomes.

3. Which human characteristic exhibits continuous variation?

  1. ABO blood group
  2. Ability to roll tongue
  3. Height
  4. Type of earlobe
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Answer: C

Height is controlled by multiple genes and environmental factors, displaying a continuous spectrum of intermediate values.

4. During which phase of meiosis does crossing over occur to generate genetic variation?

  1. Prophase I
  2. Metaphase I
  3. Anaphase II
  4. Telophase II
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Answer: A

Crossing over occurs during Prophase I between non-sister chromatids of homologous chromosomes.

5. Which condition is caused by a gene mutation resulting from a base substitution in the gene coding for hemoglobin?

  1. Down syndrome
  2. Sickle cell anemia
  3. Turner syndrome
  4. Klinefelter syndrome
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Answer: B

Sickle cell anemia is caused by a specific gene mutation (point substitution) in the beta-globin gene.

6. Which mechanism during Metaphase I generates unique allele combinations in gametes through random alignment of homologous pairs?

  1. Independent assortment
  2. DNA replication
  3. Cytokinesis
  4. Nondisjunction
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Answer: A

Independent assortment aligns homologous chromosome pairs randomly along the metaphase plate.

7. What primary genetic mechanism causes Down syndrome in humans?

  1. Base substitution during DNA replication
  2. Nondisjunction of chromosome 21 during meiosis
  3. Crossing over during mitosis
  4. Inversion of sex chromosomes
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Answer: B

Down syndrome is caused by nondisjunction of chromosome 21 during gametogenesis, resulting in trisomy 21.

8. Which characteristic represents discontinuous variation in humans?

  1. Body weight
  2. Intelligence Quotient (IQ)
  3. Presence of attached or free earlobes
  4. Skin tone
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Answer: C

Earlobe type is a discrete trait with distinct categories (free or attached) and no intermediate states.

9. Which event during sexual reproduction ensures that each zygote inherits a unique combination of paternal and maternal genes?

  1. Binary fission
  2. Random fertilization of an egg by a sperm cell
  3. Mitotic cell division
  4. Budding
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Answer: B

Random fertilization combines any one of millions of unique sperm with a unique egg cell.

10. Which statement correctly describes discontinuous variation?

  1. It is controlled by polygenes and strongly influenced by environment
  2. Phenotypes show distinct categories with no intermediate forms
  3. It is represented graphically by a continuous bell-shaped curve
  4. Features can be measured on a numerical scale such as kilograms
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Answer: B

Discontinuous variation produces clear, discrete categories (e.g., blood types) without intermediate stages.

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