Genetics and Heredity Quiz

Grade 8 · Science · Quiz

10 questions covering genotypes, phenotypes, dominant/recessive traits, and Punnett square predictions.

Questions

  1. Which scientist is known as the 'father of genetics' for his work with pea plants?

    1. Charles Darwin
    2. Gregor Mendel
    3. James Watson
    4. Louis Pasteur
    Show answer

    Answer: Gregor Mendel

    Gregor Mendel discovered the principles of heredity through systematic pea plant experiments in the 1860s.

  2. What is a gene?

    1. A type of protein in the nucleus
    2. A segment of DNA that codes for a specific trait
    3. The physical appearance of an organism
    4. The number of chromosomes in a cell
    Show answer

    Answer: A segment of DNA that codes for a specific trait

    Genes are specific DNA sequences located on chromosomes that provide instructions for producing traits.

  3. In genetics, uppercase letters represent dominant alleles.

    Show answer

    By convention, uppercase letters (A, B, T) represent dominant alleles and lowercase letters (a, b, t) represent recessive alleles.

  4. A Punnett square cross of BB × bb produces which genotype in ALL offspring?

    1. BB
    2. bb
    3. Bb
    4. Half BB and half bb
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    Answer: Bb

    All offspring receive one B from the BB parent and one b from the bb parent, giving 100% Bb (heterozygous).

  5. What is the phenotypic ratio for a Tt × Tt cross (T = tall dominant)?

    1. 1 tall : 3 short
    2. 3 tall : 1 short
    3. 1 tall : 1 short
    4. All tall
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    Answer: 3 tall : 1 short

    The cross produces TT, Tt, Tt, tt — TT and both Tt are tall (3), only tt is short (1).

  6. An organism with two identical alleles for a gene (AA or aa) is called ___.

    Show answer

    Homozygous means both alleles are the same; two dominant (AA) or two recessive (aa).

  7. Which term describes the genetic makeup (allele combination) of an organism?

    1. Phenotype
    2. Genotype
    3. Chromosome
    4. Mutation
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    Answer: Genotype

    Genotype refers to the actual allele combination (like Tt or BB), while phenotype is the visible trait.

  8. Two parents with the same phenotype cannot produce offspring with a different phenotype.

    Show answer

    Two heterozygous parents (Tt × Tt) look tall (same phenotype) but can produce short offspring (tt) — 25% chance.

  9. What are chromosomes?

    1. Proteins that build cell walls
    2. Structures in the nucleus made of DNA that carry genes
    3. The small subunits of DNA
    4. Organelles that produce energy
    Show answer

    Answer: Structures in the nucleus made of DNA that carry genes

    Chromosomes are condensed DNA structures in the cell nucleus; humans have 46 (23 pairs).

  10. A plant is homozygous recessive for flower color (pp = white). If crossed with a homozygous dominant plant (PP), what color will all the offspring be?

    1. White
    2. Half white, half purple
    3. Purple
    4. A mix of colors
    Show answer

    Answer: Purple

    All offspring will be Pp — heterozygous. Since P (purple) is dominant, all offspring show purple phenotype.

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