Genetics and Heredity: TEAS Practice Question with Answer & Explanation

Understanding Genotypes vs. Phenotypes

To excel in the Biology section of the TEAS, you must distinguish between the genetic code (genotype) and the physical expression of that code (phenotype).

Why "B" is the Correct Answer

A genotype refers specifically to the genetic makeup of an individual—the actual alleles inherited from the parents. Terms such as heterozygous (having two different alleles, like Aa), homozygous dominant (two identical dominant alleles, like AA), and homozygous recessive (two identical recessive alleles, like aa) are descriptions of a genotype. Option B identifies a "heterozygous allelic pair," which describes the code itself rather than the result of that code.

Analysis of Incorrect Options

• A) Attached earlobes: This is a phenotype. It describes a visible physical characteristic that you can observe by looking at a person.
• C) The physical appearance of a plant: This is the literal definition of a phenotype. While the genotype determines the appearance, the appearance itself is the phenotype.
• D) Curly hair texture: Similar to option A, this is an expressed trait that can be observed. It is a phenotype.

The TEAS Concept: Mendelian Genetics

On the TEAS, you will often be asked to identify examples or definitions related to heredity. Remember these relationships:

1. DNA/Genes: The source material.
2. Alleles: Different versions of a gene (e.g., the "blue" version vs. the "brown" version of an eye color gene).
3. Genotype: The specific combination of alleles (the "blueprint").
4. Phenotype: The observable trait resulting from the genotype (the "house" built from the blueprint).

Study Tip: The "PH" and "G" Mnemonics

• PHenotype = PHysical characteristic (What you see).
• Genotype = Genetic code (The actual letters used in a Punnett square).

When you see terms like "heterozygous," "homozygous," or letter combinations like Bb, think Genotype. When you see descriptive adjectives like "tall," "blue," or "smooth," think Phenotype.