Quiz 4/20

Question 1

In mammals, what percentage of the cytosine is methylated?

Answer 1

2-7%

Question 2

What does DNA methylation do to gene expression?

Answer 2

It usually silences it

Question 3

Barr body is highly ____________

Answer 3

methylated

Question 4

In DNA methylation, how is the protein prevented from binding?

Answer 4

A methyl group is in the major groove and hinders protein binding

Question 5

Which two enzymes are affected by methylation?

Answer 5

1. HpaII
2. MspI

Question 6

Describe the DNA methylation process

Answer 6

1. Forms 5’- methylcytosine
2. hemimethylated or fully methylated

Question 7

CpG islands are located where?

Answer 7

Near the promoter region

Question 8

Methylation of CpG islands is closely related to what process?

Answer 8

gene expression

Question 9

What are housekeeping genes?

Answer 9

CpG islands that are unmethylated

Question 10

What are tissue-specific genes?

Answer 10

CpG islands that are only methylated when not expressed

Question 11

The binding of the activator is prevented how?

Answer 11

Methylation of CpG islands

Question 12

Methylated CpG islands recruit which proteins that compact DNA?

Answer 12

methyl-CpG-binding proteins

Question 13

Methylated DNA sequences are inherited during ___________________.

Answer 13

Cell division

Question 14

De novo methylation or demethylation is rarely observed and a highly regulated way to control specific ___________________ during development or _____________________________.

Answer 14

gene expression, tissue-specific gene expression.

Question 15

Newly-made DNA is
A. Not methylated
B. Methylated

Answer 15

B. Methylated

Question 16

Double-stranded DNA is what type of methylated?

Answer 16

hemimethylated

Double-stranded DNA is also FULLY methylated

Question 17

Which enzyme is responsible for maintenance methylation on the daughter strand?

Answer 17

methyltransferase

Question 18

What is Imprinting?

Answer 18

Erasure and re-establisment

Question 19

How is imprinting expressed?

Answer 19

Inherited through methylation of DNA

Question 20

What is an insulator?

Answer 20

An insulator is a segment of DNA that functions as a boundary between two genes

Question 21

Explain how insulators inhibit change and block effects from neighboring enhancers.

Answer 21

1. Barrier to chromatin-remodeling or histone-modifying enzymes
2. Block the effects of enhancers of neighboring genes

Question 22

How do insulators block the effects of enhancers of neighboring genes?

Answer 22

Loop formation (called looping)

Question 23

What does the ENCODE project stand for?

Answer 23

Encyclopedia of DNA Elements

Question 24

Who funded the ENCODE project?

Answer 24

The National Human Genome Research Insitute (NHGRI)

Question 25

Who funded the Human Genome Project?

Answer 25

The National Insitute of Health and the Department of Energy

Question 26

What were the goals of the ENCODE Project? And what specifically?

Answer 26

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

Question 27

Basically, the regulation of translation is an

Answer 27

Ion-response element

Question 28

In the uptake of iron into a mammalian cell, what does Iron bind to?

Answer 28

Transferrin

Question 29

When Iron enters the cell, which complex binds to which receptor that is located where?

Answer 29

1. Iron-transferrin complex
2. Transferrin receptor
3. the membrane

Question 30

How is the Iron-transferrin-receptor complex taken into the cell?

Answer 30

by endocytosis

Question 31

After iron passes the cell membrane, it is released where?

Answer 31

Into the cytoplam

Question 32

Why is iron important to the cell? (name 2 reasons)

Answer 32

1. May be used by enzymes for reactions
2. Iron may be stored by ferritin

Question 33

The Iron regulatory protein (IRP) binds to where? (name 2)

Answer 33

1. To the Iron Response Element (IRE) of transferrin
2. To ferritin mRNAs

Question 34

The Iron Response Element (IRE) is located where on ferritin mRNA?

Answer 34

The 5’ untranslated region (5-UTR)

Question 35

When iron levels are low, what processes occur? (via ferritin)

Answer 35

IRP (iron regulatory protein) binds to the IRE of ferritin mRNA and BLOCKS the translation of ferritin protein (which is what stores iron)

Question 36

When iron levels are high, what processes occur? (via ferritin)

Answer 36

Since Iron is present, iron binds to the IRP (regulatory protein), makes that protein inactive, and the ferritin protein (which stores iron) is translated

Question 37

The Iron Response Element (IRE) is located where on receptor mRNA?

Answer 37

Located in the 3’ untranslated region (3-UTR)

Question 38

Iron control via the transferrin receptor responds to low iron by (name 2)

Answer 38

1. IRP binds to IRE of the transferrin receptor mRNA
2. Translation is transferrin receptor is created

Question 39

Iron control via transferrin receptor responds to high iron by (name 2)

Answer 39

1. Iron (when present) binds to IRP (makes inactive)
2. Degradation of transferrin receptor mRNA via endonuclease (no translation)

Question 40

Which enzyme digests transferrin receptor mRNA when iron is high?

Answer 40

endonuclease