The DNA Connection

Characteristics of DNA•Found in all living organisms.•The code is made up of genes that are used to make proteins.

•Proteins determine the physical traits and controls all cell functions.

•Genes are inherited from parent to offspring, half come from each parent.

The Genetic Code•DNA is made up of four different nitrogen bases:

A – adenine T – thymine G – Guanine C – Cytosine•A gene is a section of DNA that codes for one specific protein.

•The order of nitrogen bases determines which protein is produced.

A pairs with TG pairs with C

The Genetic Code

RNA – ribonucleic acidTwo types:Messenger RNA (mRNA) – copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm.

Transfer RNA (tRNA)–carries amino acids to the ribosome and adds them to the growing protein.

DNA vs. RNADNA RNA

•Double stranded•Adenine (A) pairs

with thymine (T)

• Single stranded• Uracil (U) replaces

thymine (T) – so A pairs with U

How Cells Make Protein1. In the nucleus,

mRNA is created by copying one half of the DNA strands.

2. The mRNA strand moves to the cytoplasm where it attaches to a ribosome that will move down the strand to read the code.

How Cells Make Protein3. The ribosome reads

the code on the mRNA and attaches tRNA molecules that match the code.

4. Each tRNA molecule carries an amino acid. As the code is read, a chain of amino acids grows into a protein.

Protein formation video