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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 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.

2. Which human trait is controlled by polygenic inheritance?

  1. ABO blood group
  2. Fingerprint patterns
  3. Body mass
  4. Eye color in fruit flies
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Answer: C

Body mass is quantitative and governed by multiple genes acting additively alongside environmental factors.

3. 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).

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. What occurs during nondisjunction in meiosis?

  1. Chromosomes replicate twice instead of once
  2. Homologous chromosomes or sister chromatids fail to separate properly
  3. DNA polymerase substitutes adenine with cytosine
  4. Centromeres divide prematurely during interphase
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Answer: B

Nondisjunction is the failure of chromosomes or chromatids to separate during cell division, leading to abnormal chromosome numbers.

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. Which environmental factor directly influences human skin color variation under prolonged exposure?

  1. Atmospheric pressure
  2. Ultraviolet (UV) radiation
  3. Ambient water humidity
  4. Wind velocity
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Answer: B

UV radiation stimulates melanocytes in the skin to produce more melanin, darkening skin tone.

8. An individual with Klinefelter syndrome possesses which chromosomal constitution?

  1. 45, XO
  2. 47, XXY
  3. 47, XYY
  4. 46, XY
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Answer: B

Klinefelter syndrome is a genetic condition where a male inherits an extra X chromosome (47, XXY).

9. What type of graph is used to display data collected for discontinuous variation in a class?

  1. Line graph
  2. Histogram with touching bars
  3. Bar chart with separate bars
  4. Scatter plot
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Answer: C

Discontinuous data consists of distinct categories, represented visually using discrete bar charts with spaces between bars.

10. 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.

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