class 10: transcription
DESCRIPTION
SBI4U Molecular Genetics. Class 10: Transcription. From Friday…. What is the Central Dogma?. Central Dogma. Fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins. Why is gene expression important?. - PowerPoint PPT PresentationTRANSCRIPT
Class 10:
Transcription
SBI4UMolecular Genetics
From Friday…
What is the Central Dogma?
CENTRAL DOGMA
Fundamental principle of molecular genetics,
which states that genetic information
flows from DNA to RNA to proteins
Why is gene expression important?
The Genetic Language Uses 4 Letters Written Into 3-Letter Words
What will be the chain of Amino Acids for the
following mRNA sequence?
AUGUGCAACCGUCGAUAG
Today we are going to talk about…
TRANSLATION
INTRODUCTION
During transcription the DNA code is chemically rewritten as an RNA code
Transcription: divided into 3 sequential stages
1. Initiation2. ElongationTermination
INITIATIONIn prokaryotes and eukaryotes
begins with RNA polymeraseBinds to the DNA strand, unwinds
the helix near the beginning of a gene
The binding occurs at the promoter which is a nucleotide sequence that lies just before the gene
A key to the promoter sequence in the eukaryotes is TATA box
TATA BOXA region of the DNA with high
percentage of TA bases, which is recognized by the RNA polymerase
Prokaryotes have a TATAAT sequenceA and T because 2 hydrogen bonds,
less energy needed to break RNA expends less energy
The part of the gene that is transcribed into RNA is called the Transcription Unit
ELONGATIONNo primer needed 5’ to 3’ directionThe opposite strand of DNA is
known as the coding strand, it contains the same base pair sequence as the new RNA
RNA elongates as nucleotides are added one at a time
The new RNA molecule winds temporarily with template DNA into hydrid RNA/DNA double helix
ELONGATION CONTINUED..Beyond this region RNA unwinds
from DNA
When a cell requires a particular protein they need to produce thousands or even millions of copies example.
A single red blood cell contains 375 million hemoglobin molecules
TERMINATION• Transcription is terminated when RNA polymerase recognizes the termination sequence
• In prokaryotes 1 termination mechanism involves a protein binding to the mRNA and stopping transcription or when mRNA binds with itself in a hairpin loop
• In eukaryotes 1 termination is string of A
• The newly made RNA descoiatates from the DNA template