1. Intro to Transcription
Protein Synthesis
Intro to Transcription

2. REVIEW- DNA Structure & Replication
A nucleotide does NOT contain:
A. a 5-carbon sugar
B. an amino acid
C. a nitrogen base
D. a phosphate group
The bonds that hold the two strands of DNA together come from:
A. the attraction of phosphate groups for each other
B. strong bonds between nitrogenous bases and the sugar-phosphate backbone
C. weak hydrogen bonds between nitrogenous bases
D. carbon-to-carbon bonds in the sugar portion of the nucleotides
In chromosomes, DNA is tightly coiled around proteins called:
A. DNA polymerase
B. chromatin
C. Chromosomes
D. Histones

3. Human DNA Model 8 Phosphates 8 Sugars 2 Adenines 2 Thymines 2 Guanines
2 Cytosines

4. Transcription
Transcription is the synthesis (making of) an RNA molecule from a DNA template.
It occurs in three steps:
1. Initiation
2. Elongation
3. Termination

5. The starting molecule We know that DNA is Double Stranded
The bases in the primary strand match up to those in the complimentary strand.
Practice:
Primary strand: A T C G C T T A G
Complimentary:

6. Transcription- 1st Step: Initiation
The enzyme Helicase unzips the two strands of DNA and separates them into two parts.
Each strand serves as a new template
IMPORTANT!
DNA contains: RNA contains:
Deoxyribose sugar Ribose sugar
Phosphate phosphate
4 nitrogenous bases (A,T,C,G) 4 nitrogenous bases (A,U,C,G)

7. Transcription- 2nd step: elongation
RNA Polymerase forms a strand of mRNA that is complementary to the starting DNA strand.

8. Transcription- 3rd step: Termination
At the end of a gene, RNA polymerase encounters a sequence of DNA called a Termination Signal or Stop codon.
There are 3 stop codons in the genetic code
UAG, UAA, UGA
RNA polymerase detaches from the DNA and translation begins.

9. Transcription: practice
Original Strand of DNA
Top Strand (DNA)
Bottom Strand (DNA) A T G C A T G C T A C G