Genetics and DNA Quiz

Grade 8 · Science · Quiz

Test your knowledge of DNA structure, inheritance patterns, and genetic concepts.

Questions

  1. What are the four nitrogen bases found in DNA?

    1. Adenine, Thymine, Cytosine, Guanine
    2. Adenine, Uracil, Cytosine, Guanine
    3. Adenine, Thymine, Cytosine, Uracil
    4. Adenine, Thymine, Ribose, Guanine
    Show answer

    Answer: Adenine, Thymine, Cytosine, Guanine

    DNA contains adenine (A), thymine (T), cytosine (C), and guanine (G). RNA replaces thymine with uracil (U).

  2. A pea plant has the genotype Tt (T = tall is dominant, t = short is recessive). What is the phenotype of this plant?

    1. Short
    2. Tall
    3. Medium height
    4. Cannot be determined
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    Answer: Tall

    Since T (tall) is dominant, even one T allele is enough to produce the tall phenotype in a Tt (heterozygous) individual.

  3. If both parents are carriers (Bb) for a recessive trait, what percentage of offspring would show the recessive phenotype?

    1. 0%
    2. 25%
    3. 50%
    4. 75%
    Show answer

    Answer: 25%

    A Bb × Bb cross produces: BB (25%), Bb (50%), bb (25%). Only bb (25%) shows the recessive phenotype.

  4. Genes are segments of DNA that code for specific proteins.

    Show answer

    Answer: True

    Genes are specific sequences of DNA nucleotides that serve as instructions for building proteins that carry out cell functions.

  5. Which organelle in the cell contains most of the DNA?

    1. Mitochondria
    2. Ribosome
    3. Nucleus
    4. Cell membrane
    Show answer

    Answer: Nucleus

    The nucleus is the cell's control center and contains the chromosomes (DNA) that hold the genetic information.

  6. What is a mutation?

    1. A change in the DNA sequence of a gene
    2. The process of copying DNA during cell division
    3. The transfer of genes between cells
    4. The expression of a recessive allele
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    Answer: A change in the DNA sequence of a gene

    A mutation is any alteration in the DNA base sequence; it may be caused by errors in replication, radiation, or chemicals.

  7. The scientist known as the 'father of genetics' for his work with pea plants is Gregor ______.

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    Answer: mendel

    Gregor Mendel (1822-1884) discovered the principles of heredity through careful experiments with garden peas, earning him the title 'father of genetics'.

  8. Which base pairs with guanine (G) in DNA?

    1. Adenine (A)
    2. Thymine (T)
    3. Cytosine (C)
    4. Uracil (U)
    Show answer

    Answer: Cytosine (C)

    In DNA, guanine (G) always pairs with cytosine (C) through three hydrogen bonds — a fundamental rule of complementary base pairing.

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