Genes and Chromosomes worksheet with questions and diagrams.

Let’s go through each question one by one, using simple science facts you’ve likely learned in class.

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1. What is a gene?

A gene is like a tiny instruction manual inside your body that tells your cells how to make something — like what color your eyes should be or how tall you might grow. Genes are passed down from your parents and help decide your traits.

→ Answer: A gene is a section of DNA that carries instructions for making a specific trait (like eye color or height).

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2. What are genes made of and what do they do?

Genes are made of DNA — which stands for deoxyribonucleic acid. Think of DNA as a long ladder twisted into a spiral (called a double helix). The rungs of the ladder are made of chemicals called bases (A, T, C, G), and the order of these bases is the code that makes up each gene.

What do they do? They tell your body how to build proteins, which are the building blocks and workers of your body — everything from muscles to enzymes that digest food.

→ Answer: Genes are made of DNA. They carry instructions for building proteins, which control your traits and body functions.

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3. Every person has two copies of each gene, one inherited from each parent. These two, almost identical genes are called ________.

When you get one copy from mom and one from dad, those two versions of the same gene are called “alleles.” Sometimes they’re exactly the same, sometimes slightly different — like one allele for brown eyes and one for blue.

→ Answer: alleles

*(Note: The diagram shows “a”, “b”, “c” as possible alleles from mum and dad — so it’s hinting at this term.)*

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4. ________ are forms of the same gene with small differences in their sequence of DNA bases because they come from two different people – your parents.

This is just repeating the idea from #3 — but now asking for the word again. Again, the answer is “alleles.”

→ Answer: Alleles

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5. The physical appearance of an organism, the organism’s traits such as size, shape, colour or behaviour is called a ________.

This is describing what you can actually see — like if someone has curly hair, freckles, or is tall. That’s called the “phenotype.”

→ Answer: phenotype

*(The shell picture shows different colors/shapes — that’s phenotype!)*

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6. What is a genotype?

Your genotype is the actual genetic code you have inside your cells — the combination of alleles you got from your parents. You can’t see it just by looking at someone — you’d need to test their DNA. For example, even if someone has brown eyes (phenotype), their genotype could be “BB” or “Bb”.

→ Answer: A genotype is the set of genes (or alleles) an organism has for a particular trait — it’s the genetic makeup hidden inside the cells.

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7. ________ type describes the physical characteristics that we can see when we look at an organism, ________ type is hidden inside the cells, inside the cells’ nucleus, and can only be seen with a microscope.

First blank = what you can see → phenotype

Second blank = what’s hidden inside → genotype

→ Answer: Phenotype, Genotype

*(The DNA image on the right shows chromosomes and genes inside the nucleus — that’s where genotype lives!)*

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Final Answer:

1. A gene is a section of DNA that carries instructions for making a specific trait (like eye color or height).
2. Genes are made of DNA. They carry instructions for building proteins, which control your traits and body functions.
3. alleles
4. Alleles
5. phenotype
6. A genotype is the set of genes (or alleles) an organism has for a particular trait — it’s the genetic makeup hidden inside the cells.
7. Phenotype, Genotype