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Genotype vs. Phenotype — Reading Comprehension

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This NGSS-aligned reading passage for middle school explains the important difference between genotype (the set of genes an organism carries) and phenotype (the observable traits). Students learn how alleles, dominant and recessive genes, and environmental influences work together to shape what we see. The passage includes real-world examples like eye color and height, and explains why some

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In genetics, the terms genotype and phenotype help us understand how traits are passed from parents to offspring and how they appear in living things. While they are closely related, they mean different things.

A genotype is the set of genes an organism carries. It is made up of alleles, which are versions of a gene inherited from each parent. Genotypes are written using letters. For example, a person might have a genotype of BB, Bb, or bb for a certain trait. Even though we can’t see a genotype just by looking at someone, it holds the instructions for traits like eye color, height, and blood type.

A phenotype, on the other hand, is the set of observable traits—what you can see or measure. For example, having brown eyes, curly hair, or being 5 feet tall are all phenotypes. These traits are influenced by both the genotype and the environment. A person might have the genes to be tall, but if they don’t get the right nutrients while growing up, they may not reach that height.

It’s also possible for two individuals to have the same phenotype but different genotypes. For instance, someone with BB or Bb genotype will both show the dominant trait, such as brown eyes. Only someone with bb will show the recessive trait, like blue eyes.

Understanding the difference between genotype and phenotype helps scientists predict how traits will appear in future generations. It also plays an important role in fields like medicine, agriculture, and evolutionary biology.

Fun Fact: You can have a genotype for dimples but not show them—some traits need both copies of the gene to appear in your phenotype!

What does a genotype describe?

Visible traitsBehavior patternsThe genes an organism carriesNutritional needs

What is a phenotype?

A type of mutationThe set of observed traitsHidden parts of DNAThe way cells divide

Which pair shows a genotype?

Brown eyes5 feet tallBbDimples

What influences a phenotype?

Only environmentOnly genotypeGenes and environmentBlood type

How can two people have the same phenotype but different genotypes?

Genes don’t matterThey have different parentsDominant alleles can hide recessive onesThey live in the same climate

Which genotype will show a recessive trait?

BBBbbBbb

What is the main idea of the passage?

Genotype and phenotype are the sameGenes are more important than traitsGenotype and phenotype describe how traits are inherited and shownOnly phenotypes are useful in science

How is this concept useful in agriculture?

To make food taste betterTo choose traits for future plantsTo stop growth in cropsTo water plants faster