Imprinting 3 better

Question 2

Why can women suffer from haemophilia?

Answer 2

The mutant x chromosome may be activated and the normal one inactivated

Question 3

Four stages of inactivation?

Answer 3

Establishment, maintenance, reading, erasure

Question 4

Three stages of x inactivation establishment in diploid cells?

Answer 4

Counting, choice, stabilisaiton

Question 5

Why is the counting phase necessary in x inactivation?

Answer 5

Must inactivate all X chromosomes except 1 (might have 3 and so need to inactivate 2)

Question 6

What happens regarding the progeny of a cell that has done the x inactivation?

Answer 6

They will all have the same x chromosome(s) inactivated and the same x chromosome activated

Question 7

Which gene is the x inactivation centre near?

Answer 7

Xist

Question 8

Which gene is the x inactivation centre opposite?

Answer 8

Tsix

Question 9

How far on either side of the Xist gene is the critical region for x inactivation?

Answer 9

150kB

Question 10

What happens if there is a deletion or mutation in the x inactivation centre?

Answer 10

That x chromosome does not become inactivated

Question 11

What happens if the choice component of the x inactivation centre is put into other regions of the genome?

Answer 11

They can inactivate other genes

Question 12

What type of RNA is Xist transcribed into?

Answer 12

lncRNA

Question 13

What type of RNA is Tsix transcribed into?

Answer 13

lncRNA

Question 14

What is the locational relationship between Tsix and Xist regarding their transcription?

Answer 14

They are expressed in opposite orientation to one another

Question 15

How much of Tsix and Xist are produced prior to inactivation?

Answer 15

Very low levels

Question 16

Role of Tsix?

Answer 16

Reduce Xist expression

Question 17

What role does Xist have in gene activation?

Answer 17

can silence genes/chromosomes

Question 18

What happens to Tsix expression on the active X once the inactive X is turned off?

Answer 18

Tsix is no longer required

Question 19

Why is Tsix no longer required once inactivation has occured?

Answer 19

Epigenetic mechanisms lock the inactive X into being silenced

Question 20

Which stage of X inactivation doesn’t require Xist?

Answer 20

Maintainance

Question 21

X inactivation state in pluripotent embryonic stem cells?

Answer 21

Both Xs are active

Question 22

Tsix and Xist expression in embryonic stem cells?

Answer 22

Both are expressed

Question 23

What happens to Xist and Tsix expression in stem cell differentiation?

Answer 23

One chromosome expresses a lot more Xist

Question 24

What does Xist RNA do to the inactive X chromosome?

Answer 24

Coats it

Question 25

Sex of tortoiseshell cats?

Answer 25

Always female

Question 26

What are DMRs?

Answer 26

Differentially methylated regions (where one allele of a gene on one chromosome is more/less methylated than the sister allele on the other chromosome)

Question 27

Full "lollipop" on gene expression diagram?

Answer 27

Methylated gene

Question 28

Hollow "lollipop" on gene expression diagram?

Answer 28

Non-methylated gene

Question 29

When do primordial germ cells lose their methylation?

Answer 29

When they are migrating to the genital ridge

Question 30

What are the most hypomethylated cells?

Answer 30

Primordial germ cells on their way to the genital ridge

Question 31

What helps imprints to be maintained after fertilization and ensures they won't be erased?

Answer 31

Maternal zygotic factors