1. 13.3 RNA & Gene Expression I. An Overview of Gene Expression A. RNA
1. Ribonucleic Acid – essential in taking the genetic information from DNA & building proteins
B. Gene Expression
1. the manifestation of genes into specific traits
II. DNA vs. RNA
A. RNA differs in three ways

2. 1. only one stranded
2. contains ribose instead of deoxyribose
3. has uracil (U) instead of thymine (T)
III. Types of RNA
A. Messenger RNA (mRNA)
1. Complementary to DNA
2. carries instructions for making a protein from a gene & delivers them to the site of translation
B. Transfer RNA (tRNA)
1. reads the mRNA sequence
2. translates the mRNA sequence into a specific sequence of amino acids
C. Ribosomal RNA (rRNA)
1. found only in ribosomes

3. IV. Transcription
A. the making of RNA from the info in DNA
B. happens in nucleus of eukaryotic cells
C. Begins at promoter (start signal of DNA)
D. RNA polymerase unwinds & separates the gene (section of DNA)

4. E. Follows the base pairing rules with the
E. Follows the base pairing rules with the change of uracil (U) for thyamine (T) creating a complementary strand of mRNA
F. Eventually reaches the stop location
G. Results in a single strand of mRNA
V. The Genetic Code: Three Letter “Words”
A. Codon
1. each three nucleotide sequence
2. each codon is matched up to 1 of amino acids

5. 3. Examples
a. AUG codes for
b. CAU codes for
c. AGU codes for
d. UGA codes for
start
histidine
serine
stop

6. VI. Translation
A. uses the info in RNA to make a specific protein
B. happens in cytoplasm of eukaryotic cells
C. Occurs in a sequence of steps, involves three kinds of RNA, & results in a complete polypeptide