Download Section 5-4

Section 5-4
Genes, DNA, and Proteins
The Genetic Code
• The main function of genes is to control the
production of proteins
– A gene is a section of DNA
– DNA is made of four nitrogen bases
• Adenine (A) pairs with Thymine (T)
• Guanine (G) pairs with Cytosine (C)
– The order of nitrogen bases along a gene with code for a
type of protein
• Every three nitrogen bases codes for one amino acid (the small
molecules that make a protein).
How Cells Make Proteins
• RNA
– Made of four nitrogen bases
• Adenine (A) pairs with Uracil (U)
• Guanine (G) pairs with Cytosine (C)
– Messenger RNA is a molecule that transfers the
information on DNA to the ribosomes
– Transfer RNA is a molecule that brings the amino
acids to the ribosomes
Translating the Code
• The Four Steps
1. DNA in the nucleus “unzips” and the Messenger RNA
makes a copy (A to U and C to G)
2. Messenger RNA then travels to the ribosomes
3. Molecules of Transfer RNA bring amino acids to the
ribosomes
4. Both Messenger and Transfer RNA line up according to
the code and the ribosome puts the amino acids
together to form a protein
Mutations
• Damage to the DNA can cause the cell to
produce the wrong type of protein.
– If a gene that controls cell division gets mutated it
can lead to cancer (tumor)