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WorksheetYear 10Level 3 · Challenge

Free Year 10 Genetics: DNA, Genes, Chromosomes and Punnett Squares Worksheet

Students describe the structure of DNA and use base pairing rules to write complementary strands, then explain how DNA, genes, chromosomes and alleles are related. They use the terms genotype, phenotype, homozygous, heterozygous, dominant and recessive, and complete Punnett squares to predict the ratios and probabilities of offspring for pea plants, sex inheritance and a recessive genetic condition.

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Year
Year 10
Subject
Science
Topic
Cells & Classification
Difficulty
Level 3 · Challenge
Estimated time
45 minutes
Curriculum
Australian Curriculum
Questions
20
Answers
Included, with working
Format
PDF (A4), print or complete online

Students will practise

  • describing the structure of DNA and the base pairing rules
  • explaining the relationship between DNA, genes, chromosomes and alleles
  • using the terms genotype, phenotype, homozygous and heterozygous
  • distinguishing dominant and recessive alleles
  • completing Punnett squares to predict offspring ratios and probabilities
  • explaining how sex is inherited

Curriculum: Australian Curriculum. We show specific outcome codes only where they have been verified against the official curriculum document.

What's next?

Completed: Genetics: DNA, Genes, Chromosomes and Punnett Squares

  1. 1Mitosis and Meiosis: How Cells Divide
  2. 2Mutations, Variation and Natural Selection

How to use this worksheet

  1. Print the PDF or complete it on screen. Write the student's name and date at the top.
  2. Read the instructions for each part together before starting. Encourage working to be shown.
  3. Mark with the answer sheet. Use the model answers and success criteria as a guide rather than a single right answer.
  4. Record the score, celebrate what went well, then follow the "What's next" suggestion.

Common questions

Who is this worksheet for?

Year 10 students (typically ages 15–16) working on cells & classification. It is pitched at level 3 · challenge.

Are the answers included?

Yes. The PDF includes a full answer sheet with model answers and success criteria where there is more than one good answer. You can also view the answers online.

How long does it take?

About 45 minutes for 20 questions. Short, regular sessions work best: two or three a week beats one long one.

Do I need to sign up to download?

No. Click Download Free PDF and it opens immediately. It is free for personal, classroom and homeschool use.

What should we do next?

Try Mitosis and Meiosis: How Cells Divide.

Preview

Success TutoringWorksheetsYear 10 · Science · Cells & Classification

Genetics: DNA, Genes, Chromosomes and Punnett Squares

Name

Date

Score /

Show every Punnett square. Ratios are expected values: real numbers of offspring vary by chance.

Part A: DNA, genes and chromosomes

DNA (deoxyribonucleic acid) is made of two strands twisted into a double helix. Each strand is a chain of units containing one of four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). The bases on the two strands pair up: A with T and C with G.

The order of the bases is a code. A gene is a section of DNA that codes for a protein, and proteins help determine characteristics. Each chromosome is one very long DNA molecule carrying many genes. Chromosomes come in pairs: one of each pair comes from each parent.

1.Match each term to its meaning.
  • DNA
  • Gene
  • Chromosome
  • Allele
  • Mutation
  • One of the different versions of the same gene
  • A change in the sequence of bases in DNA
  • A long, tightly coiled strand of DNA found in the nucleus
  • The molecule that carries genetic information, shaped like a twisted ladder (a double helix)
  • A section of DNA that carries the instructions for making a particular protein
2.In DNA, the base A always pairs with (answer space), and C always pairs with (answer space).
3.Write the complementary strand for this DNA sequence: ATGCCGTA (answer space)
4.Write the complementary strand for this DNA sequence: GGATCCTA (answer space)
5.Human body cells contain 46 chromosomes. How many pairs is this, and how many chromosomes are in a human sperm or egg cell? (answer space)
6.Put these in order from largest to smallest.
  1. ANucleus, chromosome, gene, base
  2. BChromosome, nucleus, gene, base
  3. CGene, chromosome, nucleus, base
  4. DNucleus, gene, chromosome, base

Part B: Alleles, genotype and phenotype

A capital letter stands for a dominant allele and the same letter in lower case stands for the recessive allele.

7.Match each inheritance term to its meaning.
  • Genotype
  • Phenotype
  • Homozygous
  • Heterozygous
  • Dominant allele
  • Recessive allele
  • An allele that shows in the phenotype even if only one copy is present
  • An allele that shows in the phenotype only if two copies are present
  • The alleles an organism has for a characteristic, such as Pp
  • The characteristic that shows, such as purple flowers
  • Having two different alleles, such as Pp
  • Having two identical alleles, such as PP or pp
8.In pea plants, purple flowers (P) are dominant over white flowers (p). What are the possible genotypes of a purple-flowered plant? (answer space)
9.What is the genotype of a white-flowered pea plant? Explain how you know. (answer space)

Part C: Punnett squares

Draw a Punnett square for each cross: write one parent's gametes across the top and the other parent's down the side, then fill in each box.

10.Two heterozygous purple-flowered pea plants (Pp × Pp) are crossed. Complete a Punnett square and give the ratio of genotypes and of phenotypes in the offspring.
11.In the cross above, what is the probability that an offspring has white flowers? Give your answer as a fraction and a percentage. (answer space)
12.The same cross (Pp × Pp) produces 400 seeds that grow into plants. About how many would you expect to have white flowers? (answer space)
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Preview — the PDF contains the full resource and answer sheet.

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About this resource

Created by
Success Tutoring Science Team
Last reviewed
1 October 2026
How it was made
Written by our team

Free to print and share for personal, classroom and homeschool use. Please don't resell. Spotted an error? Let us know.