Chapter 3 section 4 The DNA Connection

A. The Genetic Code Main function of genes is to control the the production of proteins in cells 2. proteins help to determine the size, shape, and many other traits of the organism 3. Chromosomes are composed mostly of DNA

4. made up of four different nitrogen bases -adenine (A) -thymine(T) -guanine(G) -cytosine(C)

-the order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced 5. group of three bases codes for attachment of amino acids which are the building blocks of proteins

B. How Cells Make Proteins: 1. protein synthesis: -takes place in the ribosomes in the cytoplasm of the cell

2. The Role of RNA -A messenger must first carry the genetic code from the DNA inside the nucleus into the cytoplasm. -genetic messenger is called RNA

3. different from DNA -looks like one side of the DNA ladder -contains different sugar molecule -contains the same nitrogen bases except thymine -has uracil (U) instead

4. several types of RNA involved in protein synthesis: -messenger RNA: -copies the coded message from the DNA in the nucleus and carries the message into the cytoplasm

-transfer RNA -carries amino acids and adds them to the growing protein