control of gene expression big idea 3: living systems store, retrieve, transmit, and respond to info...
TRANSCRIPT
Control of Gene Expression
Big Idea 3: Living systems store, retrieve, transmit, and respond to
info essential to life processes.
Essential Knowledge
• 3B1: Gene regulation results in differential gene expression, leading to cell specialization.
• 3B2: A variety of intercellular and intracellular signal transmissions mediate gene expression
Much Diversity due to Gene Expression
• Each tissue in our body is very different despite having the same DNA
• Even identical twins have many differences due to gene expression
Some Basics: Regulatory Sequences
• Stretches of DNA that interact w/ regulatory proteins to control transcription.
• Allows RNA Polymerase to bind on. – AKA promoter (TATA box)
– Enhancers are sequences that increase transcription
Some Basics: Regulatory Genes
• Code for proteins or mRNAs which affect gene expression– Ex: microRNAs–Repressor proteins– Transcription factors/ enhancers
Components of the Operon
• Operator, sequence next to the promoter (On/Off switch) If repressor protein is on it, then off…can’t
make genes• Promoter (where RNA polymerase binds)
• Genes that work together
Types of Operons• Some genes are normally
“off” and can be turned “on” Presence of a molecule induces gene expression or enhances gene expression
• Some genes are normally “on” and can be turned “off” Presence of a molecule represses gene expression
Inducing Gene Expression: Lac Operon, + Control
• If lactose present, bacteria need to make lactase to break it down.
• Lactose binds to repressor on operator repressor is released from operator
• RNA polymerase now fits onto promoter region to make mRNA protein lactase.
Negative ControlCase Study: Trp Operon
• Tryptophan fits in repressor blocks RNA polymerase.
• Once out of tryp, repressor changes shape to allow promoter available to make more tryptophan turns transcription on.
In Eukaryotes…
• No operons…• Gene expression involves regulatory genes,
regulatory elements, and transcription factors. All work together to determine how much
product is made.
Transcription Factors• Bind to specific DNA sequences
• Some activate (increase expression) and some are repressors (decrease expression)
Signal Transmission
• Within and b/t cells mediates gene expression.
• Ex: cytokines regulate gene expression to allow cell replication and division.
Mr Anderson
• http://www.youtube.com/watch?v=3S3ZOmleAj0