Chapter 19: Control of Gene Expression in Eukaryotes Flashcards
Interact with the TATA box, other proteins, and RNA polymerase to form transcription initiation complex
General transcription factors
Different cell types express different subsets fo genes
Differential gene expression
Far away from the promoter (can be upstream, downstream, or in an intron)
Enhancers
What do HDACs (histone deacetylases) do?
Takes acetyl groups off
Strongly increase or decrease transcription rate
Specific transcription factors
How can histones be modified?
The addition or removal of specific chemical groups to histone tails
Loosens DNA coiling with HATs and HDACs
Acetylation (-COCH3)
Most eukaryotic genes have associated segments of noncoding DNA that serve as binding sites for proteins to start transcription
Regulatory sequences
Study of changes in gene expression not due to change in DNA sequence
Epigenetics
What percentage of protein coding genes are expressed by cells in humans?
About 20%
What are the types of regulatory sequences?
Promoter-proximal elements and enhancers
What do transcription factors do?
Bring everything together to form transcription initiation complex
Can recruit proteins for chromatin remodeling
Specific transcription factors
Have a low rate of transcription
General transcription factors
What do different cell types have for gene expression?
Different activators and repressors
What does acetylation of histones do to DNA?
Promotes loose chromatin structure that permits transcription
What can epigenetics explain?
The differences seen in identical twins and why one expresses traits and the other doesn’t or why one develops a disease and the other doesn’t
What do chromatin modifications do and not do?
Do not change the DNA sequence but may be passed on to future generations
What do genes with related functions that need to be expressed coordinately share?
A specific combo of control elements
What do all cells express?
Different genes from each other depending on their function
What does regulation of gene expression depend on?
The combination of control elements
What happens in DNA methylation?
Adds methyl groups (-CH3) to cytosine (C) residues that trigger chromatin to condense
What can influence methylation?
Environmental factors
What do HATs (histone acetyltansferases) do?
Transfer acetyl groups to histones
What do errors in remodeling after histone modification lead to?
Many different diseases including cancer
Two types of specific transcription factors that strongly increase or decrease transcription rate
Activators and repressors
What can methylated genes cause?
Play a role in cancer development
Regulatory sequences which can inhibit transcription
Silencers
What does condensed chromatin cause?
Genes to not be expressed bc transcription cant occur bc the DNA is too tightly wound
How is gene expression controlled in eukaryotes?
At many levels in different ways. The farther along you get, the more energy and resources the cell has to use
Bind to regulatory sequences
Specific transcription factors
What must happen for a gene to be expressed (transcribed)?
The cellular machinery must be able to access it
What is DNA wrapped around?
Histones
What do methyl groups added to histones cause?
DNA that is more tightly packed together
Loosens DNA coiling
Phosphorylation (PO4)
Tightens DNA coiling
Methylation (CH3)
What do activators do?
Appropriate activators bind to the control elements regardless of where the gene is in the genome
What usually happens when a gene is methylated?
It usually remains that way through successive rounds of division and can occur throughout life due to environmental factors
Essential for the transcription of all protein coding genes
General transcription factors
