Free sample activity · Grades 6–8

Genetics Basics Practice

These questions introduce genetics vocabulary and a simplified, fictional two-allele model. Real traits may involve many genes and environmental influences. This activity does not interpret personal genetic information.

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How to use this activity

Allow five to ten minutes. Use the stated model for each inheritance question; do not infer human traits or health outcomes from it. No family history or genetic test results are needed.

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Genetic information

Which molecule carries inherited biological instructions?

DNA Cellulose Water
Answer: A.

DNA stores biological information that can be passed to offspring. Cellulose is a structural material, and water is not the inherited instruction sequence.

Genes

Which description best fits a gene?

An entire organism A segment of DNA with a biological function A type of cell membrane
Answer: B.

A gene is a functional segment of DNA. Genes can provide instructions for proteins or functional RNA; a gene is not a whole organism.

Alleles

What is an allele?

A synonym for every chromosome in a cell A structure used to digest food One of the alternative versions at a particular DNA location
Answer: C.

Alleles are alternative versions of a DNA sequence at a location. In a simple gene model, A and a label two such versions.

Genotype notation

In a fictional two-allele model, what does the genotype Aa indicate?

One A allele and one a allele at the modeled gene Two A alleles No inherited alleles
Answer: A.

Aa records two different alleles at the modeled gene. This is called a heterozygous genotype.

A stated inheritance model

In a fictional plant model, each parent contributes one allele at random. One parent is Aa and the other is aa. What is the probability of an Aa offspring?

1 1/2 0
Answer: B.

The Aa parent contributes A or a with equal probability; the aa parent contributes a. The two equally likely outcomes are Aa and aa.

Interpreting dominance

In a fictional model, A is completely dominant to a. Which statement follows?

The A allele must be more common in every population. The A allele is always beneficial. An Aa plant shows the trait associated with A in this model.
Answer: C.

Complete dominance describes the trait expressed by Aa in the stated model. It does not establish an allele's frequency or whether it is beneficial.

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All questions, answers & explanations

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  1. Genetic information

    Which molecule carries inherited biological instructions?

    Answer: DNA

    DNA stores biological information that can be passed to offspring. Cellulose is a structural material, and water is not the inherited instruction sequence.

  2. Genes

    Which description best fits a gene?

    Answer: A segment of DNA with a biological function

    A gene is a functional segment of DNA. Genes can provide instructions for proteins or functional RNA; a gene is not a whole organism.

  3. Alleles

    What is an allele?

    Answer: One of the alternative versions at a particular DNA location

    Alleles are alternative versions of a DNA sequence at a location. In a simple gene model, A and a label two such versions.

  4. Genotype notation

    In a fictional two-allele model, what does the genotype Aa indicate?

    Answer: One A allele and one a allele at the modeled gene

    Aa records two different alleles at the modeled gene. This is called a heterozygous genotype.

  5. A stated inheritance model

    In a fictional plant model, each parent contributes one allele at random. One parent is Aa and the other is aa. What is the probability of an Aa offspring?

    Answer: 1/2

    The Aa parent contributes A or a with equal probability; the aa parent contributes a. The two equally likely outcomes are Aa and aa.

  6. Interpreting dominance

    In a fictional model, A is completely dominant to a. Which statement follows?

    Answer: An Aa plant shows the trait associated with A in this model.

    Complete dominance describes the trait expressed by Aa in the stated model. It does not establish an allele's frequency or whether it is beneficial.

Take it one step further

Explain why a simple two-allele diagram is useful for learning but cannot explain every real trait. Identify one assumption made by the model.

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