1. Transcription
Packet #10
Chapter #8

2. Introduction Transcription
Transcription is a process that occurs within the nucleus of a cell where a single strand of DNA is used to produce a complementary strand of RNA.
The type of RNA produced is mRNA.

3. Types of RNA mRNA Messenger RNA
An RNA molecule transcribed from the DNA of a gene
Once mRNA is complete, proteins are translated from mRNA by the help of RIBOSOMES
Types of RNA
mRNA
snRNA
tRNA
rRNA

4. The Gene

5. Chromosome Review DNA strands are composed of segments known as genes.
Chromatin
DNA Molecules
DNA Strands
Genes

6. Genes
Genes, used during the process of transcription, have two major segments.
Regulatory region
Coding region
Both regions play a role during transcription.
Within the regulatory region, there is a special region known as the promoter region.
DNA Strands
Genes
Regulatory Region
Promoter Region
Coding Region
Terminator

7. Strands of Transcription
Template Strand
In transcription, known as the Complementary Strand (cDNA)
A molecular “mold” that shapes the structure or sequence of another molecule
Controls the nucleotide sequence of RNA during transcription
Alignment guide
“GUIDE”

8. Strands of Transcription
Complementary Strand (cDNA)
DNA transcribed from a specific RNA strand
Complementary Strand (cRNA)
RNA transcribed from a specific DNA single-stranded template

9. Transcription
The Process

10. The Process
RNA Polymerase, the only enzyme used during transcription, binds at the promoter region (sequence) and unzips the DNA strand
RNA Polymerase works downstream adding RNA nucleotides to the 3’ end of the newly formed RNA strand
New RNA strand grows in the 5’ to 3’ direction
RNA Polymerase hits the “Terminator” sequence that signals the end of transcription
Newly made RNA is released.
This RNA is called pre-mRNA.

11. Post-Transcription

12. Post-Transcription I The new RNA strand is called pre-mRNA
Why? Because the pre-mRNA needs to be “groomed” for the moment of Translation
Unneeded RNA nucleotide segments, known as introns, need to be removed.

13. Post-Transcription II
The introns are removed and the exons, the good regions, are joined together in a process known as splicing.
Process completed using the enzyme known as spliceosome.
Spliceosome contains snRNA.
The completed mRNA leaves the nucleus and enters into the cytoplasm ready for translation.
The mRNA carries the genetic code with it.
Pre-mRNA contains both introns and exons.
Introns
The “Junk in the Trunk”
Regions of the RNA strand that must be removed, via splicing, and will not be used during Translation
Exons
Regions of RNA that WILL be used and translated into amino acids during TRANSLATION

14. Review