Genetics and Heredity

Grade 7 · Science · Study Guide

Explore how traits are inherited from parents to offspring through genes, alleles, and Punnett squares.

Genetics is the study of how traits — characteristics like eye color, hair texture, or height — are passed from parents to their children. The instructions for these traits are stored in DNA, which is organized into structures called genes. Humans have about 20,000 to 25,000 genes, each carrying the code for a specific trait.

Each gene can have different versions called alleles. You inherit one allele from your mother and one from your father, giving you a pair for every gene. When two alleles are the same, an organism is homozygous for that trait. When they are different, it is heterozygous. Some alleles are dominant (they show up even when only one copy is present) while others are recessive (they only show up when two copies are inherited).

Scientists use a Punnett square — a simple grid — to predict the probability of offspring inheriting certain traits. Gregor Mendel, a 19th-century monk who studied pea plants, discovered these rules of inheritance and is known as the Father of Genetics.

Key terms

Gene
A segment of DNA that carries the instructions for a specific trait.
Allele
One of two or more versions of a gene (e.g., B for brown eyes vs. b for blue eyes).
Dominant
An allele that is expressed even when only one copy is present, typically written with a capital letter.
Recessive
An allele that is only expressed when two copies are inherited, written with a lowercase letter.
Punnett Square
A grid used to predict the probability of offspring inheriting specific allele combinations.

Flashcards

Genetics
The study of how traits are passed from parents to offspring.
DNA
The molecule that carries genetic instructions for the development and function of living things.
Gene
A section of DNA that codes for a specific trait.
Allele
A variant form of a gene (e.g., B or b).
Dominant Allele
Expressed whenever present; written as a capital letter.
Recessive Allele
Only expressed when two copies are present; written as a lowercase letter.
Homozygous
Having two identical alleles for a trait (BB or bb).
Heterozygous
Having two different alleles for a trait (Bb).

Questions

  1. Where is genetic information stored in a cell?

    1. In the cell membrane
    2. In the mitochondria
    3. In DNA
    4. In the cytoplasm
    Show answer

    Answer: In DNA

    Genetic information is stored in DNA, which is found in the nucleus of the cell.

  2. A recessive trait will show up in offspring even if only one recessive allele is inherited.

    Show answer

    Answer: False

    A recessive trait only appears when two recessive alleles are inherited (one from each parent). One recessive allele paired with a dominant allele will not show the recessive trait.

  3. The scientist known as the Father of Genetics is Gregor ___.

    Show answer

    Answer: mendel

    Gregor Mendel conducted famous experiments with pea plants in the 1860s, establishing the laws of inheritance that form the basis of modern genetics.

  4. If B is dominant (brown eyes) and b is recessive (blue eyes), what eye color does a Bb individual have?

    1. Blue
    2. Brown
    3. Green
    4. Half blue, half brown
    Show answer

    Answer: Brown

    B (brown) is dominant over b (blue). A Bb individual has one dominant allele, so the dominant trait (brown eyes) is expressed.

  5. An organism with two identical alleles (like BB or bb) is called:

    1. Heterozygous
    2. Recessive
    3. Homozygous
    4. Hybrid
    Show answer

    Answer: Homozygous

    Homozygous means both alleles are the same — either both dominant (BB) or both recessive (bb). Heterozygous means they are different (Bb).

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