Unit 17: Eukaryotic Gene Regulation Flashcards
What are four reasons why differential gene expression is important?
- Responsible for forming specialized cell types.
- Arranging cell types into tissues.
- Coordinating cell types into tissues.
- Form multicellular society we call an individual.
At what three levels can eukaryotes control gene expression?
- Transcriptional
- Chromatin remodeling and regulatory DNA sequences. - Post-transcriptional
- RNA processing
- mRNA stability - Post-translational
________ must be “_______” when gene product is needed so the genes are accessible to __ _________.
Chromatin must be “remodeled” when gene product is needed so the genes are accessible to RNA polymerase
What does chromatin consist of?
Chromatin consists of DNA complexed with proteins.
What are histones?
Most abundant DNA-
associated proteins. Can be modified to control how tightly DNA wraps around them.
Why must chromatin be decondensed?
Chromatin must be decondensed to expose promoter for RNA polymerase to bind.
What did Weintraub and Groudine test about chromatin decondensing?
Tested chromatin decondensing using DNase.
1. Enzyme it used to cut DNA at random locations.
2. It cannot cut tightly condensed DNA.
3. It preferentially cuts genes that are actively being transcribed.
What are three major ways to remodel chromatin?
- DNA methylation
- Histone modification
- Chromatin-remodeling complexes
What is DNA methylation of remodeling chromatin? (3 things)
- DNA methyltransferases add methyl groups (-CH₃) to cytosines that are next to guanines (called CpG sites).
- These methylated CpG sites are like signals that attract proteins.
- These proteins make the chromatin tighter (condensed), which blocks gene expression.
What is histone modification of remodeling chromatin? (2 things)
- Enzymes add variety of chemical groups to histones (acetyl groups, methyl groups, phosphate groups/short peptide chains).
- Can promote either condensation or decondensation.
What is a histone code?
A histone code of particular modifications sets the state of condensation for genes.
What is acetylation of histones?
Acetylation of histones is usually associated with activation of genes.
What is chromatin-remodeling complexes of remodeling chromatin? (2 things)
- Major player in chromatin alteration and gene regulation.
- Reshape chromatin
- May cause nucleosomes to slide along DNA
- May knock histones completely off DNA - They open up stretches of chromatin and allow gene expression.
How are patterns of methylation and acetylation passed on?
Patterns of methylation and acetylation are passed on when a cell divides.
What is epigenetic inheritance?
Any inheritance mechanism that is not due to differences in DNA sequences.
Different sets of _________ ___ ______ are commonly involved in eukaryotic ____ ________.
Different sets of regulatory DNA sequences are commonly involved in eukaryotic gene regulation.
What is the core promoter region?
The core promoter region, containing the TATA box and other sequences, is right next to the transcription start site to the start of transcription; these bind RNA polymerase II (pol II) and its associated
general transcription factors.
Where are enhancer and silencer sequences?
At greater distances from the core promoter are the enhancer and silencer sequences (or enhancers and silencers).
What are enhancers?
Enhancers activate gene expression.
What are silencers?
Silencers repress gene expression.
What do enhancers and silencers bind with?
They bind to regulatory transcription factor proteins and interact with proteins bound to other promoter segments.
Why do different types of cells express different genes?
Different types of cells express different genes because they have different transcription factors.
What are gene encoding transcription factors expressed in response from?
Genes encoding transcription factors are expressed in response
to signals from other cells.
_______ TFs bind to _______.
Activator TFs bind to Enhancers.
