Genetics: chromosomes, genes and DNA — KCSE Biology

KCSE Biology · 92 practice questions · 3 syllabus objectives

34 easy44 medium14 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Define chromosome, gene, allele, and DNA

Describe the structure of DNA (double helix)

Genetics: chromosomes, genes and DNA

Sample Questions

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easySHORT ANSWER5 marks

State two characteristics of individuals with Down's syndrome.

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Part (a) — 5 marks

Intellectual disability / mental retardation (1 mk)

Short stature / stocky build (1 mk)

Flat face with a flattened nose bridge (1 mk)

Epicanthic folds / slanting eyes (1 mk)

Short broad hands with a single palm crease (1 mk)

easySHORT ANSWER3 marks

Define each of the following terms as used in genetics: (a) Genotype (b) Recessive (c) Homozygous

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Part (a) — 3 marks

Correct definition of Genotype (1 mk)

Correct definition of Recessive (1 mk)

Correct definition of Homozygous (1 mk)

easySHORT ANSWER4 marks

Explain how the sex of a male child is determined in human beings.

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Part (a) — 4 marks

Human females have sex chromosomes XX and males have XY (1 mk)

During meiosis, the father produces two types of sperm: those carrying X and those carrying Y chromosome (1 mk)

If an X-bearing sperm fertilizes the ovum (which always carries X), the offspring is XX (female); if a Y-bearing sperm fertilizes the ovum, the offspring is XY (male) (1 mk)

Therefore the sex of the child is determined by the type of sperm from the father (1 mk)

Define each of the following terms as used in genetics: (a) Gene (b) Phenotype (c) Homozygous

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Why Practise Genetics: chromosomes, genes and DNA?

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Genetics: chromosomes, genes and DNA — KCSE Biology

What You'll Learn

Sample Questions

+89 More Questions

Why Practise Genetics: chromosomes, genes and DNA?

KNEC Aligned

Detailed Marking Schemes

Track Your Mastery

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