12-3 RNA and Protein Synthesis
Page 300

A. Introduction
• 1. Chromosomes are a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

A. Introduction
• 2. Genes are coded DNA instructions that control the production of proteins within the cell.

B. The Structure of RNA
• 1. RNA (Ribonucleic Acid) is similar to DNA because they are BOTH long chains of nucleotides.
• REVIEW: What are the 3 parts of a nucleotide?

B. The Structure of RNA
• 2. There are 3 major differences between DNA and RNA:

DNA RNA

C. 3 Types of RNA
• 1. Messenger RNA (mRNA) carries the coded information from genes on DNA to the rest of the cell.

PRACTICE!!!
• A A A A T T T T T G G G C C C
• A T G C A T G A C T G A C T G
• A C T G C A T G C G T A C G T

C. 3 Types of RNA
• 2. Ribosomal RNA (rRNA) are part of the structure of a ribosome where proteins are made.

C. 3 Types of RNA
• 3. Transfer RNA (tRNA) transfers each amino acid to the ribosome as it is specified by coded messages in the in mRNA.

D. Transcription
• 1. Process of copying part of the nucleotide sequence of DNA into a complementary sequence in RNA.

D. Transcription
• 2. Requires an enzyme called RNA Polymerase which binds to DNA and separates DNA strands.

D. Transcription
• 3. RNA Polymerase uses 1 strand of DNA as a template from which nucleotides are assembled into a strand of RNA.

D. Transcription
• 4. Promoters are specific base sequences that signal to RNA Polymerase where to begin transcription.

E. RNA Editing
• 1. After RNA is transcribed, it needs to be edited so that only the sections that code for proteins are used.

E. RNA Editing
• 2. Introns are not involved in coding for proteins and are removed from RNA chains.

E. RNA Editing
• 3. Exons code for proteins and are kept in RNA chains because they are “expressed” in protein synthesis.

F. The Genetic Code
• 1. Proteins are made by joining amino acids into long chains called polypeptides .

F. The Genetic Code
• 2. The genetic code of mRNA is read in groups of 3 letters called codons.

F. The Genetic Code
• 3. Each codon codes for a specific amino acid
(there are 20 total).

G. Translation
• 1. Decoding mRNA into a polypeptide
(protein).
• LETS PRACTICE!
• AUG-GGG-CCC-UAA
• AUG-UGU-CAG-UAG

G. Translation
• 2. Before translation can occur, mRNA is transcribed and edited in the nucleus before being released into the cytoplasm.

G. Translation
• 3. mRNA attaches to a ribosome and moves through one codon at a time.

G. Translation
• 4. As the codons move through the ribosome, tRNA molecules deliver the matching amino acid to build the polypeptide chain.

G. Translation
• 5. tRNA carry an anticodon that is complementary to the codon of the mRNA.

G. Translation
• 6. The polypeptide chain continues to grow until it reaches a STOP codon.