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Secondary 4 Pure Biology Genetics Inheritance Quiz

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Questions

Secondary 4 Pure Biology Quiz - Genetics Inheritance

Name: __________________________
Class: __________________________
Date: __________________________
Score: _______ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
The number of marks for each question or part question is given in brackets [ ] at the end of the question.

Section A: Multiple Choice (Questions 1–5)

Choose the correct answer and write the letter in the box provided.

1. Which of the following statements correctly describes the relationship between DNA, genes, and chromosomes?

	DNA	Gene	Chromosome
A	Double helix	Section of DNA	Made of proteins only
B	Single strand	Whole chromosome	Contains many genes
C	Double helix	Section of DNA	Contains many genes
D	Double helix	Protein structure	Contains one gene

Answer: [ ] [1]

2. In a species of pea plant, the allele for tall stems (T) is dominant to the allele for short stems (t). Two heterozygous tall plants are crossed. What is the probability that an offspring will have short stems?

A. 0%
B. 25%
C. 50%
D. 75%

Answer: [ ] [1]

3. A man with blood group A and a woman with blood group B have a child with blood group O. What are the genotypes of the parents?

A. $I^A I^A$ and $I^B I^B$
B. $I^A I^O$ and $I^B I^O$
C. $I^A I^O$ and $I^B I^B$
D. $I^A I^A$ and $I^B I^O$

Answer: [ ] [1]

4. Which row correctly identifies the sex chromosomes found in a normal human male and a normal human female?

	Male	Female
A	XX	XY
B	XY	XX
C	XY	XY
D	XX	XX

Answer: [ ] [1]

5. Haemophilia is a sex-linked recessive condition. A woman who is a carrier for haemophilia marries a man who does not have the condition. What is the chance that their son will have haemophilia?

A. 0%
B. 25%
C. 50%
D. 100%

Answer: [ ] [1]

Section B: Structured Questions (Questions 6–15)

6. The diagram below represents a short section of a DNA molecule.

Image pending generation for this question.

      Base 1      Base 2      Base 3      Base 4
         |           |           |           |
    -----A-----------G-----------C-----------T-----
         |           |           |           |
    -----T-----------C-----------G-----------A-----

(a) Name the type of bond that holds the two strands of DNA together.
_________________________________________________________________________ [1]

(b) If Base 1 is Adenine (A), what is the complementary base on the opposite strand?
_________________________________________________________________________ [1]

_________________________________________________________________________ [1]

7. Cystic fibrosis is a genetic disorder caused by a recessive allele ( $f$ ). The normal allele is dominant ( $F$ ).

(a) Define the term allele.

_________________________________________________________________________ [1]

(b) Two parents who do not have cystic fibrosis have a child with the disorder.
(i) State the genotype of the child.
_______________________________________________________________________ [1]

(ii) Determine the genotypes of the parents. Show your working using a genetic diagram.

Answer space

_________________________________________________________________________ [3]

8. The ABO blood group system in humans is controlled by three alleles: $I^A$ , $I^B$ , and $I^O$ . $I^A$ and $I^B$ are codominant, and both are dominant to $I^O$ .

(a) Explain what is meant by the term codominant.

_________________________________________________________________________ [1]

(b) A man with blood group AB marries a woman with blood group O.
(i) State the genotype of the man.
_______________________________________________________________________ [1]

(ii) State the genotype of the woman.
_______________________________________________________________________ [1]

(iii) What are the possible blood groups of their children?
_______________________________________________________________________ [1]

9. Mitosis and meiosis are two types of cell division.

(a) State one difference between the cells produced by mitosis and the cells produced by meiosis in terms of genetic composition.

_________________________________________________________________________ [1]

(b) State the number of chromosomes in a human gamete formed by meiosis.
_________________________________________________________________________ [1]

_________________________________________________________________________ [2]

10. The diagram below shows the pedigree of a family for a specific genetic trait.

Image pending generation for this question.

(Note: Square = Male, Circle = Female, Shaded = Affected, Unshaded = Unaffected)

Generation I:   [1] Unshaded Male  x  [2] Unshaded Female
                         |
Generation II:  [3] Shaded Male   [4] Unshaded Female   [5] Unshaded Male

(a) Is the trait dominant or recessive? Give a reason for your answer.

_________________________________________________________________________ [2]

(b) Using N for the dominant allele and n for the recessive allele, state the genotype of individual 1.
_________________________________________________________________________ [1]

11. Genetic engineering involves modifying the genetic material of an organism.

(a) Name the enzyme used to cut DNA at specific sequences.
_________________________________________________________________________ [1]

(b) Name the enzyme used to join DNA fragments together.
_________________________________________________________________________ [1]

(c) State one advantage of producing human insulin using genetically engineered bacteria compared to extracting insulin from pigs.

_________________________________________________________________________ [1]

12. Variation in humans can be continuous or discontinuous.

(a) Define continuous variation.

_________________________________________________________________________ [1]

(b) Give one example of continuous variation in humans.
_________________________________________________________________________ [1]

(c) Give one example of discontinuous variation in humans.
_________________________________________________________________________ [1]

13. A mutation is a change in the genetic material.

(a) Name one factor that can increase the rate of mutation.
_________________________________________________________________________ [1]

(b) Sickle cell anaemia is caused by a mutation in the gene for haemoglobin. Explain how this mutation affects the red blood cells.

_________________________________________________________________________ [2]

14. In cats, the allele for black fur (B) is dominant to the allele for white fur (b). A black cat is crossed with a white cat. All the offspring are black.

(a) State the genotype of the white parent.
_________________________________________________________________________ [1]

(b) State the genotype of the black parent.
_________________________________________________________________________ [1]

(c) If two of the offspring from this cross are bred together, what is the expected phenotypic ratio of the next generation?
_________________________________________________________________________ [1]

15. Describe the structure of a chromosome.

_________________________________________________________________________ [2]

Section C: Free Response Questions (Questions 16–20)

16. Explain how the structure of DNA allows it to replicate accurately.

_________________________________________________________________________ [3]

17. Distinguish between genotype and phenotype, using an example to illustrate your answer.

_________________________________________________________________________ [3]

18. Describe the process of protein synthesis, including the roles of DNA and mRNA.

_________________________________________________________________________ [4]

19. Discuss the ethical concerns associated with genetic engineering in humans.

_________________________________________________________________________ [3]

20. A couple has three sons. They are expecting a fourth child.
(a) What is the probability that the fourth child will be a girl?
_________________________________________________________________________ [1]

(b) Explain why the gender of the previous children does not affect the gender of the fourth child.

_________________________________________________________________________ [2]

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Answers

Secondary 4 Pure Biology Quiz - Genetics Inheritance (Answer Key)

Total Marks: 40

Section A: Multiple Choice

1. C
Reasoning: DNA is a double helix. A gene is a section of DNA coding for a protein. Chromosomes are made of DNA and proteins and contain many genes. [1]

2. B
Reasoning: Cross $Tt \times Tt$ . Offspring: $TT, Tt, Tt, tt$ . Only $tt$ is short. 1 out of 4 = 25%. [1]

3. B
Reasoning: Child is O ( $I^O I^O$ ). Must receive $I^O$ from both parents. Parent A is $I^A I^O$ , Parent B is $I^B I^O$ . [1]

4. B
Reasoning: Males are XY, Females are XX. [1]

5. C
Reasoning: Mother is carrier ( $X^H X^h$ ), Father is normal ( $X^H Y$ ). Sons receive Y from father. Sons receive either $X^H$ or $X^h$ from mother. 50% chance of receiving $X^h$ (haemophilia). [1]

Section B: Structured Questions

6.
(a) Hydrogen bonds [1]
(b) Thymine (T) [1]
(c) To store genetic information / To code for proteins / To control cell activities. [1]

7.
(a) An alternative form of a gene. [1]
(b) (i) $ff$ [1]
(ii) Parents must be heterozygous ( $Ff$ ) because they are unaffected but produced an affected child. [1]
Genetic Diagram:
Parent Genotypes: $Ff \times Ff$ [1]
Gametes: $F, f$ and $F, f$ [1]
Offspring Genotypes: $FF, Ff, Ff, ff$
Offspring Phenotypes: 3 Normal : 1 Cystic Fibrosis.
(Correct diagram with labels earns full marks). [3]

8.
(a) Both alleles are expressed in the phenotype / Neither allele is recessive to the other. [1]
(b) (i) $I^A I^B$ [1]
(ii) $I^O I^O$ [1]
(iii) Blood Group A and Blood Group B. (Genotypes $I^A I^O$ and $I^B I^O$ ). [1]

9.
(a) Mitosis produces genetically identical cells; Meiosis produces genetically different cells. [1]
(b) 23 [1]
(c) It reduces the chromosome number by half, ensuring that upon fertilization, the diploid number is restored. / It introduces genetic variation. [2]

10.
(a) Recessive. [1]
Reason: Unaffected parents (1 and 2) have an affected child (3). If it were dominant, one parent would have to be affected. [1]
(b) $Nn$ (Heterozygous) [1]

11.
(a) Restriction enzyme [1]
(b) DNA ligase [1]
(c) Human insulin is identical to natural human insulin (less likely to cause allergic reaction) / Ethical concerns of using animals avoided / Larger scale production possible. [1]

12.
(a) Variation that shows a range of values / No distinct categories. [1]
(b) Height / Weight / Skin colour. [1]
(c) Blood group / Eye colour / Gender. [1]

13.
(a) Ionising radiation / UV light / Chemical mutagens (e.g., tar in cigarette smoke). [1]
(b) Changes the shape of haemoglobin / Red blood cells become sickle-shaped / Reduced surface area for oxygen transport / Cells block capillaries. [2]

14.
(a) $bb$ [1]
(b) $BB$ (Since all offspring are black, the black parent must be homozygous dominant). [1]
(c) 3 Black : 1 White [1]

15.
DNA molecule wrapped around histone proteins [1]
Coiled tightly to form a chromosome structure. [1]

Section C: Free Response Questions

16.

DNA strands separate / Hydrogen bonds break. [1]
Free nucleotides align opposite exposed bases via complementary base pairing (A with T, C with G). [1]
DNA polymerase joins nucleotides to form new strands. [1]
(Max 3 marks)

17.

Genotype: The genetic makeup of an organism (the alleles present). [1]
Phenotype: The physical observable characteristics of an organism. [1]
Example: Genotype $Tt$ (heterozygous) results in Phenotype Tall (if T is dominant). [1]
(Max 3 marks)

18.

DNA contains the code for proteins. [1]
DNA cannot leave the nucleus. [1]
A copy of the gene is made as mRNA (transcription). [1]
mRNA moves to the ribosome in the cytoplasm. [1]
Ribosome reads the code and assembles amino acids in the correct order to form a protein (translation). [1]
(Any 4 points)

19.

"Designer babies" / Selection of desirable traits may lead to loss of diversity. [1]
Safety concerns / Unknown long-term effects of gene editing. [1]
Ethical issue of "playing God" / Interfering with nature. [1]
Potential for discrimination against those with genetic defects. [1]
(Any 3 points)

20.
(a) 50% / 0.5 / 1/2 [1]
(b) Each fertilization event is independent. [1]
The father produces equal numbers of X and Y sperm. [1]
The chance of an X sperm fertilizing the egg is always 50%, regardless of previous outcomes. [1]
(Max 2 marks for explanation)