Quiz 4/20 Flashcards
In mammals, what percentage of the cytosine is methylated?
2-7%
What does DNA methylation do to gene expression?
It usually silences it
Barr body is highly ____________
methylated
In DNA methylation, how is the protein prevented from binding?
A methyl group is in the major groove and hinders protein binding
Which two enzymes are affected by methylation?
- HpaII
- MspI
Describe the DNA methylation process
- Forms 5’- methylcytosine
- hemimethylated or fully methylated
CpG islands are located where?
Near the promoter region
Methylation of CpG islands is closely related to what process?
gene expression
What are housekeeping genes?
CpG islands that are unmethylated
What are tissue-specific genes?
CpG islands that are only methylated when not expressed
The binding of the activator is prevented how?
Methylation of CpG islands
Methylated CpG islands recruit which proteins that compact DNA?
methyl-CpG-binding proteins
Methylated DNA sequences are inherited during ___________________.
Cell division
De novo methylation or demethylation is rarely observed and a highly regulated way to control specific ___________________ during development or _____________________________.
gene expression, tissue-specific gene expression.
Newly-made DNA is
A. Not methylated
B. Methylated
B. Methylated
Double-stranded DNA is what type of methylated?
hemimethylated
Double-stranded DNA is also FULLY methylated
Which enzyme is responsible for maintenance methylation on the daughter strand?
methyltransferase
What is Imprinting?
Erasure and re-establisment
How is imprinting expressed?
Inherited through methylation of DNA
What is an insulator?
An insulator is a segment of DNA that functions as a boundary between two genes
Explain how insulators inhibit change and block effects from neighboring enhancers.
- Barrier to chromatin-remodeling or histone-modifying enzymes
- Block the effects of enhancers of neighboring genes
How do insulators block the effects of enhancers of neighboring genes?
Loop formation (called looping)
What does the ENCODE project stand for?
Encyclopedia of DNA Elements
Who funded the ENCODE project?
The National Human Genome Research Insitute (NHGRI)
Who funded the Human Genome Project?
The National Insitute of Health and the Department of Energy
What were the goals of the ENCODE Project? And what specifically?
To identify the active and functional elements of the genome that are involved in controlling gene expression
1. Sequencing RNAs
2. ID transcription factor binding sites within DNA
3. ID DNA methylation sites
4. ID histone modification sites
5. ID DNase I recognition sites, which often overlap with TF binding sites
Basically, the regulation of translation is an
Ion-response element
In the uptake of iron into a mammalian cell, what does Iron bind to?
Transferrin
When Iron enters the cell, which complex binds to which receptor that is located where?
- Iron-transferrin complex
- Transferrin receptor
- the membrane
How is the Iron-transferrin-receptor complex taken into the cell?
by endocytosis
After iron passes the cell membrane, it is released where?
Into the cytoplam
Why is iron important to the cell? (name 2 reasons)
- May be used by enzymes for reactions
- Iron may be stored by ferritin
The Iron regulatory protein (IRP) binds to where? (name 2)
- To the Iron Response Element (IRE) of transferrin
- To ferritin mRNAs
The Iron Response Element (IRE) is located where on ferritin mRNA?
The 5’ untranslated region (5-UTR)
When iron levels are low, what processes occur? (via ferritin)
IRP (iron regulatory protein) binds to the IRE of ferritin mRNA and BLOCKS the translation of ferritin protein (which is what stores iron)
When iron levels are high, what processes occur? (via ferritin)
Since Iron is present, iron binds to the IRP (regulatory protein), makes that protein inactive, and the ferritin protein (which stores iron) is translated
The Iron Response Element (IRE) is located where on receptor mRNA?
Located in the 3’ untranslated region (3-UTR)
Iron control via the transferrin receptor responds to low iron by (name 2)
- IRP binds to IRE of the transferrin receptor mRNA
- Translation is transferrin receptor is created
Iron control via transferrin receptor responds to high iron by (name 2)
- Iron (when present) binds to IRP (makes inactive)
- Degradation of transferrin receptor mRNA via endonuclease (no translation)
Which enzyme digests transferrin receptor mRNA when iron is high?
endonuclease
