Ch 18 Genetic and Epigenetic Regulation Flashcards
What is Epigenetics?
Changes in expression in a gene or get of genes without a change in the DNA sequence
DNA Methylation of Cytosine
CPG islands if CG sequences (found in promoter sequences). When the C is methylated it inactivates transcription. Unmethylated is when transcription is on.
What is a promoter?
Sequence of DNA where DNA polymerase binds at the 5’ end.
What are the effects of DNA Methylation?
The methylated DNA attracts repressor proteins that inhibits translation. Mis-regulation is cancerous and in oncogenes and tumor suppressors
Chromatin remodeling
Acetylation of histones modifies nucleosomes to make DNA more accessible and increase transcription. When de- acylated transcription is blocked as dna is less accessible.
Why does x-Chromosome inactivation occur in females?
They have the ability to produce twice as much protein for x-linked genes. So to regulate this an X chromosome is inactivated allowing equal dosage of expressed X chromosome in males and females
Xist in X chromosome inactivation center
- The list gene is transcribed and spliced and exist noncoding RNA bings with the x-chromosome INACTIVATION center.Transcription is then allowed to continue and the x-chromosome becomes coated with Xist RNA-the presence of this triggers dna methylation to reduce transcription
Random x chromosome inactivation
Will turn one allele off so only one shows
Regulatory transcription factors
Promoter sequences and enhancer/silencer sequences
Why are transcription factors and polymerase needed in transcription?
to recognize promoter sequences
What is a common example of a promoter sequence?
The TATA box
WHY the TATA box?
Dna denaturation begins here, and T and A are easier to pull apart because only they only have two bonds
What must assemble on the chromosome before RNA polymerase can bind to the promoter?
General Transcription factors
What three things form the Transcription complex
TFIID binding to the TATA box and other transcription factors
What is the point in the transcription complex?
to bring in RNA polymerase
What is the point in the promoters, Tata box, TFIID?
To initiate transcription in Eukaryotes
An enhancer is what type of regulator?
Positive
An silencer is what type of regulator?
Negative
When can multiple genes be regulated at the same time?
When the genes share the same regulatory sequences which bind to the same transcription factor.
What is an example of multiple genes being regulated at the same time?
The SRE stressor gene- a stressor activates transcription of regulatory protein producing stress proteins instead of normal ones
What is RNA editing?
When RNA made in the cell is changed by an enzyme. The enzyme changes the base sequence of the primary therefore changing the protein it encodes for. Ex- C to U
What regulated transcription?
Promoters, T.F, enhancers, and silencers
what regulates Translations?
Micro Rnas (MiRNA) which are regulator RNA
What does miRNA do?
Binds to 3’ UTR to target mRNA and translation is inhibited
