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Genetics and Heredity Practice Tests

These Grade 9 Biology practice tests explain how DNA, genes, chromosomes, and alleles carry information from one generation to the next. Questions cover Mendelian inheritance, Punnett squares, meiosis, mutations, pedigrees, genetic variation, and basic biotechnology.

Skills covered

  • Distinguishing DNA, genes, chromosomes, alleles, genotype, and phenotype
  • Applying dominant, recessive, homozygous, heterozygous, incomplete dominance, codominance, and sex-linked inheritance concepts
  • Using Punnett squares and probability to predict possible offspring genotypes and phenotypes
  • Connecting meiosis, crossing over, independent assortment, fertilization, and chromosome number to genetic variation
  • Interpreting mutations, pedigrees, karyotypes, natural selection, and introductory genetic engineering

How to use these practice tests

Start by identifying the gene, allele, chromosome, or inheritance pattern involved. For crosses, write the parental alleles and list the possible gametes before calculating the probability. Review each explanation to strengthen genetics vocabulary and evidence-based reasoning.

For more Grade 9 Science practice, return to the Grade 9 Science category.

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Grade 9 Genetics and Heredity Practice Tests

Practice Grade 9 Science questions about DNA, genes, chromosomes, alleles, Mendelian inheritance, Punnett squares, meiosis, mutations, pedigrees, and genetic variation.

Choose the best answer. Identify the genetic information or inheritance pattern, apply the relevant rule, and use probabilities carefully when interpreting crosses.

10 Questions
0/10 Questions0 %
Correct 0
Incorrect 0
Unanswered 10
1. QuestionMultiple choice

What is incomplete dominance?

Please select an answer first.

Correct answer: A

The correct answer is The heterozygous phenotype is intermediate between the two homozygous phenotypes..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: In incomplete dominance, neither allele completely masks the other, so the heterozygote has an intermediate phenotype.
  3. Check the answer: The correct answer is The heterozygous phenotype is intermediate between the two homozygous phenotypes..

In incomplete dominance, neither allele completely masks the other, so the heterozygote has an intermediate phenotype.

2. QuestionMultiple choice

What is codominance?

Please select an answer first.

Correct answer: B

The correct answer is Both alleles are fully expressed in the heterozygote..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Codominance occurs when both alleles contribute visibly to the heterozygous phenotype, as in some blood-group patterns.
  3. Check the answer: The correct answer is Both alleles are fully expressed in the heterozygote..

Codominance occurs when both alleles contribute visibly to the heterozygous phenotype, as in some blood-group patterns.

3. QuestionMultiple choice

What is a sex-linked trait?

Please select an answer first.

Correct answer: C

The correct answer is A trait controlled by a gene located on a sex chromosome..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Sex-linked genes are located on the X or Y chromosome, so inheritance patterns can differ between males and females.
  3. Check the answer: The correct answer is A trait controlled by a gene located on a sex chromosome..

Sex-linked genes are located on the X or Y chromosome, so inheritance patterns can differ between males and females.

4. QuestionMultiple choice

In a simple recessive disorder, what is a carrier?

Please select an answer first.

Correct answer: D

The correct answer is An unaffected heterozygous individual who can pass on the recessive allele..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: A carrier has one recessive allele and may pass it to offspring without showing the recessive phenotype.
  3. Check the answer: The correct answer is An unaffected heterozygous individual who can pass on the recessive allele..

A carrier has one recessive allele and may pass it to offspring without showing the recessive phenotype.

5. QuestionMultiple choice

If two carriers for a recessive condition are crossed, what is the chance of an affected child in a simple model?

Please select an answer first.

Correct answer: A

The correct answer is 25%..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: For two heterozygous carriers, the four genotype outcomes include one homozygous recessive outcome, giving a 25% probability per pregnancy.
  3. Check the answer: The correct answer is 25%..

For two heterozygous carriers, the four genotype outcomes include one homozygous recessive outcome, giving a 25% probability per pregnancy.

6. QuestionMultiple choice

Which parent typically passes mitochondrial DNA to a child?

Please select an answer first.

Correct answer: B

The correct answer is The mother..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Mitochondria in the zygote usually come from the egg, so mitochondrial traits are generally inherited maternally.
  3. Check the answer: The correct answer is The mother..

Mitochondria in the zygote usually come from the egg, so mitochondrial traits are generally inherited maternally.

7. QuestionMultiple choice

What is a polygenic trait?

Please select an answer first.

Correct answer: C

The correct answer is A trait influenced by multiple genes..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Polygenic traits result from the combined effects of multiple genes and often show a range of phenotypes.
  3. Check the answer: The correct answer is A trait influenced by multiple genes..

Polygenic traits result from the combined effects of multiple genes and often show a range of phenotypes.

8. QuestionMultiple choice

What is a pedigree?

Please select an answer first.

Correct answer: D

The correct answer is A diagram that tracks a trait through generations of a family..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: A pedigree uses standardized symbols to represent family relationships and the inheritance of traits.
  3. Check the answer: The correct answer is A diagram that tracks a trait through generations of a family..

A pedigree uses standardized symbols to represent family relationships and the inheritance of traits.

9. QuestionMultiple choice

What does a circle usually represent in a genetic pedigree?

Please select an answer first.

Correct answer: A

The correct answer is A female..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: In standard pedigree notation, a circle represents a female and a square represents a male.
  3. Check the answer: The correct answer is A female..

In standard pedigree notation, a circle represents a female and a square represents a male.

10. QuestionMultiple choice

Why can an environmental change alter phenotype without changing genotype?

Please select an answer first.

Correct answer: B

The correct answer is Environmental conditions can affect how genes are expressed..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Temperature, nutrition, light, and other conditions can influence gene expression and observable traits without changing DNA sequence.
  3. Check the answer: The correct answer is Environmental conditions can affect how genes are expressed..

Temperature, nutrition, light, and other conditions can influence gene expression and observable traits without changing DNA sequence.

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