Did fur. Some of the cats have stripes.

Did you know that every living thing has a unique set of instructions for building its body? Learn what a genome is, what it is made of and how a genome affects what you look like in this lesson.

Genes and Genomes

Imagine that you have been invited to a kitten party.

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I hope you remember to bring some cat treats! When you get there, cats are running all over the place. One cat has long, orange fur, while another cat has very short grey fur. Some of the cats have stripes. One cat has a long fluffy tail, and another has a short stubby one.

A cats appearance is determined by its genes.


A cat’s traits, or characteristics, like fur color, fur length and tail size, are determined by its genes. Genes are sections of information on DNA that determine how an organism’s body develops. DNA is like a recipe for a living thing’s body, and genes are the individual instructions that make up the recipe.

A cat has a little over 20,000 different genes. These 20,000 instructions determine what color the cat’s eyes will be, how long its tail will grow, even what its meow will sound like.A living thing’s complete set of genetic instructions – or all of its genes – is called a genome.

A genome has all of the information needed to build an entire organism and for that living thing to grow and stay alive.

Human Genes and Genomes

Every living thing – each flower, each dog and each person – has its own unique genome. This means your genome is one of a kind. You are the only human alive with your specific set of genetic instructions.

The genetic information that makes up a genome is inherited, or passed down, from an organism’s parents. For each trait, we inherit two copies of a gene: one from our mom and one from our dad. Humans have approximately 19,000 genes.

Genomes and DNA

Even though every genome is unique, all genomes are made of the same material – DNA. That’s right, your genome is made of the same material as an earthworm or a sunflower’s. DNA is a long, twisted molecule that holds all of an organism’s genetic information. Since it holds all of the information to make and keep organisms alive, DNA is sometimes called ‘the molecule of life’.

Genomes and Cells

Your body has millions of copies of your genome, because an entire copy of a living thing’s genome is found in most of its cells.

The DNA that makes up the genome is coiled or folded into tiny bundles called chromosomes. These chromosomes are stored in the nucleus, or center, of each cell.

Most cells contain an entire copy of an organisms genome.

Lesson Summary

Genes are the individual instructions for building each piece of a living thing’s body. A living thing’s complete set of genetic instructions, or all of its genes, is called a genome.

Every living thing has a unique genome, but all genomes are made of the same material – DNA. DNA is organized into structures called chromosomes and stored in the nucleus of cells.


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