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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 does it mean when an allele is dominant?

Please select an answer first.

Correct answer: A

The correct answer is It can be expressed when at least one copy is present..

  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 dominant allele can contribute to the phenotype in a heterozygous genotype; dominance does not necessarily mean more common.
  3. Check the answer: The correct answer is It can be expressed when at least one copy is present..

A dominant allele can contribute to the phenotype in a heterozygous genotype; dominance does not necessarily mean more common.

2. QuestionMultiple choice

When is a recessive allele usually expressed in a simple Mendelian trait?

Please select an answer first.

Correct answer: B

The correct answer is When two recessive copies are present..

  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 recessive phenotype appears when an individual inherits two recessive alleles for that trait.
  3. Check the answer: The correct answer is When two recessive copies are present..

A recessive phenotype appears when an individual inherits two recessive alleles for that trait.

3. QuestionMultiple choice

What is a homozygous genotype?

Please select an answer first.

Correct answer: C

The correct answer is A genotype with two identical alleles..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Homozygous means the two alleles for a gene are the same, such as TT or tt.
  3. Check the answer: The correct answer is A genotype with two identical alleles..

Homozygous means the two alleles for a gene are the same, such as TT or tt.

4. QuestionMultiple choice

What is a heterozygous genotype?

Please select an answer first.

Correct answer: D

The correct answer is A genotype with two different alleles..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Heterozygous means the two alleles differ, such as Tt.
  3. Check the answer: The correct answer is A genotype with two different alleles..

Heterozygous means the two alleles differ, such as Tt.

5. QuestionMultiple choice

If T is dominant for tall plants, what phenotype is expected for genotype Tt?

Please select an answer first.

Correct answer: A

The correct answer is Tall..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: The dominant T allele is present in Tt, so the simple Mendelian phenotype is tall.
  3. Check the answer: The correct answer is Tall..

The dominant T allele is present in Tt, so the simple Mendelian phenotype is tall.

6. QuestionMultiple choice

If two heterozygous parents are crossed as Tt × Tt, what is the probability of tt offspring?

Please select an answer first.

Correct answer: B

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: The four equally likely combinations are TT, Tt, Tt, and tt, so one out of four is tt.
  3. Check the answer: The correct answer is 25%..

The four equally likely combinations are TT, Tt, Tt, and tt, so one out of four is tt.

7. QuestionMultiple choice

What is the purpose of a Punnett square?

Please select an answer first.

Correct answer: C

The correct answer is To predict possible offspring genotypes and their expected proportions..

  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 Punnett square organizes parental alleles to model possible offspring genotypes and probabilities.
  3. Check the answer: The correct answer is To predict possible offspring genotypes and their expected proportions..

A Punnett square organizes parental alleles to model possible offspring genotypes and probabilities.

8. QuestionMultiple choice

What happens to allele pairs during the formation of gametes?

Please select an answer first.

Correct answer: D

The correct answer is The two alleles separate so each gamete receives one 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: The law of segregation states that paired alleles separate during gamete formation.
  3. Check the answer: The correct answer is The two alleles separate so each gamete receives one allele..

The law of segregation states that paired alleles separate during gamete formation.

9. QuestionMultiple choice

What is independent assortment?

Please select an answer first.

Correct answer: A

The correct answer is The separation of one chromosome pair is generally independent of other chromosome pairs..

  1. Identify the genetics concept: Determine whether the question asks about DNA, alleles, inheritance, meiosis, variation, or genetic evidence.
  2. Apply the inheritance principle: Independent assortment during meiosis contributes to genetic variation by producing different combinations of chromosomes in gametes.
  3. Check the answer: The correct answer is The separation of one chromosome pair is generally independent of other chromosome pairs..

Independent assortment during meiosis contributes to genetic variation by producing different combinations of chromosomes in gametes.

10. QuestionMultiple choice

What is a test cross used to determine?

Please select an answer first.

Correct answer: B

The correct answer is The unknown genotype of an individual showing a dominant phenotype..

  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 dominant-phenotype individual can be crossed with a homozygous recessive individual to reveal whether the unknown genotype is homozygous or heterozygous.
  3. Check the answer: The correct answer is The unknown genotype of an individual showing a dominant phenotype..

A dominant-phenotype individual can be crossed with a homozygous recessive individual to reveal whether the unknown genotype is homozygous or heterozygous.

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