Genes & DNA
Each chromosome contains smaller units known as genes, which are ordered the same way in all humans.
- There are about 30,000 different genes in humans.
- Each gene has a specific job to do in the body.
- Like chromosomes, genes occur in pairs. One is found on the chromosome from the mother, and the other is on the chromosome from the father.
DNA is the chemical that makes up your genes. The DNA has two strands linked by bonds, much like rungs on a ladder. The chemical bonds fit together in a specific pattern, like pieces of a puzzle. DNA contains the genetic instructions for the body to develop and function. DNA instructions are like a recipe for making a person.
Nucleotides
The puzzle pieces are called nucleotides (new-klee-o-tides). There are four different kinds of nucleotides: A, C, T, and G.
- A and T always fit together.
- C and G always fit together.
Pairs of puzzle pieces line up to form a ladder. The ladder is then tightly twisted into what's called a helix. The helix is twisted even more into a coil to form a chromosome.
