DNA and Inheritance

This lesson covers: 

  1. Where DNA is found and what it does
  2. How genes decide our characteristics
  3. How we get our DNA from our parents
  4. The discovery of DNA's structure

Chromosomes, genes, and DNA

DNA is the genetic material that determines all of your unique traits and characteristics.


The DNA passed down from your parents is what makes you who you are.

Diagram showing the relationship between chromosomes, genes, and DNA within a cell nucleus.
  • DNA molecules are located inside the nucleus of each of your cells.
  • Within the nucleus, DNA is packaged into structures called chromosomes.
  • Chromosomes are made of tightly coiled strands of DNA.
  • Along the DNA molecule are small segments called genes.
  • Genes are the sections of DNA that carry the codes for specific characteristics.

Genes

Genes are special bits of DNA that decide how certain parts of us develop and look.


For example, genes decide things like:

  • Hair colour
  • Eye colour
  • Height


So, you have typically two copies of each gene, one from your mother and one from your father, and they work together to decide your traits.

Inheriting DNA - Why you look a bit like your parents

You get your DNA from both of your parents, which is why you might look like them or have similar traits.

Diagram showing inheritance of DNA through egg and sperm cells with 23 chromosomes each forming a fertilised egg with 46 chromosomes in 23 pairs.

Here's how you get DNA from your parents:

  1. Most human body cells have 46 chromosomes, set up in 23 pairs.
  2. Egg cells and sperm cells have just 23 chromosomes each.
  3. When an egg and sperm join, the chromosomes come together.
  4. This makes a new cell with 23 pairs of chromosomes, one set from each parent.
  5. The genes on these chromosomes mix traits from your parents.
  6. This way of passing on genes from parents to children is called heredity.


Even though every new person is a mix of their parents' DNA, you can still see where the DNA came from across many generations.

The discovery of DNA's structure

The shape and structure of DNA were figured out in 1953.

Illustration of the DNA double helix structure with two strands.

Two scientists named Watson and Crick found out that DNA has a shape like a twisted ladder, known as a double helix.


They used data from other scientists Franklin and Wilkins to build a model of DNA.


This discovery was important because:

  • Knowing the shape of DNA helped scientists figure out how it can copy itself.
  • It explained how genetic information is stored and passed on.
  • This knowledge led to modern genetics which has helped develop new medical treatments.