Shemanko Lecture 4

Question 1

How does the cell remember what genes to turn back on when polymerase 11 leaves the dna and stops transcribing genes?

Answer 1

Through bookmarks- epigenetic markers and protein partners that leave instruction the genes

Question 2

Can bookmarks be reprogrammed?

Answer 2

yes through micro-environments and cancer

Question 3

What is heterochromatin, what is euchromatin?

Answer 3

Chromatin that remains tightly packed after mitosis is called heterochromatin
Euchromatin is chromatin returns to a dispersed state after mitosos

Question 4

What do chromosomes consist of?

Answer 4

chromatin fibers, histones, and dna and histones are organized into subunits called nucleosomes

Question 5

What does histone H1 do?

Answer 5

links nucleosomes

Question 6

What is the structure of nucleosomes?

Answer 6

Dna is wrapped around a core complex, this complex has two of each histone H2A, H2B, H3, H4. Has histone H1 outside of it linking it to other nucleosomes

Question 7

What is the structure of histones?

Answer 7

Each histone has a flexible amino-terminal tail that sticks out past DNA

Question 8

What do histones do?

Answer 8

Can modify character of nucleosomes
Histones, regulatory proteins and enzymes help mediate DNA transcription, compaction, replication, recombination, and repair

Question 9

What is the histone code?

Answer 9

Histone tail modifications; tails of histones can recruit nonhistone proteins which changes the way histones of neighboring nucleosomes interact this includes phosphorylation, acetylation, methylation, or ubiquitenation

Question 10

What is the histone code hypothesis?

Answer 10

states that the activity of a chromatin region depends on the degree of modification of the histone tails

Question 11

Can small RNA’s silence chromatin?

Answer 11

yes by recruiting proteins that modify histones

Question 12

How is DNA and histones methylated?

Answer 12

A methyl group is added to the 5 carbon position of cytosine residues in DNA by DNA methyl transferases
Histones are methylated on arginine anD LYSINE residues by histone methyl transferases.

Question 13

How are histones acetylated?

Answer 13

by actylation on lysine through HAT (histone acetyl transferases)

Question 14

How are histones deactylated?

Answer 14

by deacetylation on lysine through HDAC (histone deacetylases)

Question 15

What opens chromatin?

Answer 15

acetylation

Question 16

What closes chromatin?

Answer 16

deacetylation or methylation

Question 17

Histone acetyl transferases lead to what?

Answer 17

open chromatin

Question 18

Histone deacetylases or histone methyltransferases lead to what?

Answer 18

closed chromatin

Question 19

What kind of machinery does open chromatin allow room for?

Answer 19

allows for room for transcription machinery to find their binding sites

Question 20

If H3K9 is methylated what happens?

Answer 20

the chromatin becomes closed after recruiting heterochromatin protein 1.

Question 21

Is H3K9 is acetylated what happens?

Answer 21

The chromatin becomes open

Question 22

What is HP1?

Answer 22

heterochromatin protein 1, contains a chromodomain which binds to methylated histones

Question 23

Any protein that has a chromodomain will do what?

Answer 23

bind to methylated amino acids

Question 24

How does a cell know which genes were on before the cell cycle occurs and drops polymerase during mitossi?

Answer 24

through epigenetic markers

Question 25

What is a Barr body?

Answer 25

Is a X chromosome that remains condensed and doesn’t become transcriptionally active

Question 26

How does a Barr body form?

Answer 26

The XIC gene produces XIST RNA which then coats the X chromosome, triggering histone methylation and therefore chromosome inactivation.

Question 27

What are proginetor cells?

Answer 27

are more specialized then stem cells but as not specialized as cells that have differentiated

Question 28

How can the mammary gland microenvironment can reprogram cells of other tissues?

Answer 28

you clear out the epithelial lineage cells in the mammary gland and the microenvironment will change gene expression of the new cell, reopen up genes that were inhibited and cause it to be mammary gland cell?