Meiosis, Gametes & Genetic Variation — Practice · Grade 7 Science

Chapter: Genes, Cell Division & Heredity

What this practice covers

By the end of Meiosis, Gametes & Genetic Variation you should be able to:

8 questions, written answer, multiple choice and numeric, each with a worked explanation.

Vocabulary used: meiosis, gamete, diploid, haploid, recombination.

Problem 1

Why is “any random half of the chromosomes” inadequate?
Answer and explanation

A functional gamete in this simplified normal model needs one representative of each type, not an arbitrary subset missing some types.

Problem 2

Why is one mitotic division not a sufficient meiosis model?
Answer and explanation

It normally preserves the paired set rather than producing the reduced gamete set through the studied two-division process.

Problem 3

Does reshuffling necessarily create a new allele sequence?
Answer and explanation

No. It can combine existing versions differently. A mutation changes genetic material; these are distinct processes.

Problem 4

Why is reduction relevant before gamete fusion?
Answer and explanation

It permits the paired set to be restored rather than repeatedly doubling the set across generations in this model.

Problem 5

Illustrative species has eight chromosomes in a diploid body cell, arranged in four pairs. Normal gametes form and two fuse. Find gamete and zygote counts and explain how different gametes can carry different combinations.
Answer and explanation

Each modeled gamete has four chromosomes; fusion yields a zygote with eight. Different pair distributions and exchanges can produce varied combinations despite equal counts. Equal chromosome count does not imply identical allele versions. The conclusion assumes the stipulated normal diploid life cycle, not every organism’s reproductive arrangement.

Divide the paired set into one per pair: four.

Combine two gamete sets: four plus four equals eight.

Connect distributions with varied inherited combinations.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A diagram gives an eight-chromosome species eight in each gamete and sixteen in the zygote. What missing process should be examined?
Answer and explanation

The diagram omitted chromosome-set reduction during meiosis in the stated diploid model. Normal gametes should have four and the zygote eight.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which set belongs to a normal gamete of the fictional six-chromosome diploid species?
  1. Six paired chromosomes
  2. Three, one from each pair
  3. Twelve
  4. No genetic material
Answer and explanation

Three, one from each pair

Reduction gives three chromosomes, one representative of each modeled pair.

Problem 8

A fictional diploid species has ten chromosomes. How many are in a normal gamete?
Answer and explanation

5 chromosomes

Ten arranged in five pairs yields one per pair: five.

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