1. What is central dogma? From DNA to Protein
All proteins consist of polypeptide chains
A linear sequence of amino acids
Each chain corresponds to the nucleotide base sequence of a gene

2. What is the first step?
1. Transcription: Enzymes uses base sequence of a gene as template to make strand of RNA
Two DNA strands unwind in a specific region
RNA polymerase assembles strand of RNA
Covalently bonds RNA nucleotides (adenine, guanine, cytosine, uracil) according to nucleotide sequence of exposed gene

3. What is the second step? 2. Translation
Information in the RNA strand is decoded (translated) into a sequence of amino acids

4. Prokaryotes and eukaryotes
In prokaryotic cells (no nucleus)
Transcription and translation occur in cytoplasm
In eukaryotic cells
Genes are transcribed in the nucleus
Resulting mRNA is translated in the cytoplasm

5. Three types of RNA Messenger RNA (mRNA)
Carries protein-building codes from DNA to ribosomes
Ribosomal RNA (rRNA)
Forms ribosomes (where polypeptide chains are assembled)
Transfer RNA (tRNA)
Delivers amino acids to ribosomes

6. RNA and DNA compared DNA exists as double-stranded molecules
hereditary information
double helix
contains deoxoyribose sugar
RNA
Disposable copies of hereditary information and some are catalytic
exists as a single stand.
contains ribose instead of deoxyribose
contains uracil in place of thymine

7. RNA Modification: Alternative Splicing
Before mRNA leaves the nucleus:
Introns are removed
Some exons are removed along with introns; remaining exons are spliced together in different combinations
Poly-A tail is added to 3’ end of new mRNA

8. What is the genetic code?
Messenger RNA (mRNA) carries DNA’s protein-building information to ribosomes for translation
mRNA’s genetic message is written in codons
Sets of three nucleotides along mRNA strand

9. Codons Codons specify different amino acids
A few codon signals stop translation
Sixty-four codons constitute a highly conserved genetic code