Genotype vs. Phenotype Lesson for Kids: Definitions & Examples

Instructor: Lindsy Frazer

Dr. Frazer has taught several college level Science courses and has a master's degree in Human Biology and a PhD in Library and Information Science.

The terms genotype and phenotype not only sound similar they are also closely related. Learn how an organism's genetic makeup -its genotype- affects its appearance or phenotype in this lesson.


Imagine waking up to a thump on the roof. You peek your head out your bedroom window and see an alien!

How would you describe your visitor to your friends? You might talk about his green skin or big black eyes!

When we describe how an organism, or living thing, looks we are describing its phenotype. Phenotype is the physical properties of an organism, everything you can observe from how they look to how they act. You can remember that phenotype is all about the physical because phenotype and physical both start with ''ph.''


But, what determines an organism's phenotype? It's mostly about genes. Not the kind you wear, but the kind found deep in your cells.

Genes are sections of information on DNA that determine how an organism's body will develop. You can think of DNA as an instruction manual for the body and genes as the specific instructions. Many living things inherit two genes for every characteristic from their parents - one copy from their father and one copy from their mother. These genes come in pairs like your socks. But unlike your socks, the genes in a pair are not always identical. One might be a striped sock and the other might be plain white. These different copies, or versions, of a gene are called alleles. Different combinations of alleles will make different phenotypes.

The entire set of genes, including the specific alleles, found in an organism's DNA is known as its genotype . So an organism's genotype is the specific set of instructions it carries around in its cells.


Fly on the Wall

Flies have genes that code, or have instructions, for the shape of their wings. One allele of the wing shape gene codes for straight wings - we call this allele S - while another version of the gene codes for wrinkled wings (called W). A fly's genotype - the specific pair of wing shape alleles it has - will determine if it has a straight wing or wrinkled wing phenotype.


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