DNA methylation developmeant and disease, lecture 12

Question 1

What are some epigenetic markers?

Answer 1

Methylation, demethylation, histone acetylation, histone deacetylation

Question 2

What does methylation and demmethylation do?

Answer 2

Methylation silence genes by blocking transcription factors from acessing parts of the DNA and demethylation removes methyl groups to acess the DNA for transcription.

Question 3

What does histone acetylation and histone deacetylation do?

Answer 3

Histone acetylation is when acetyl groups atatch to the histones making it less coiled and enabling transcription factors to acess the DNA. Histone deacetylation is when these acetyl groups are removed from the histones making them more tightly wrapped unabling transcription.

Question 4

Are epigenetic markers inherited?

Answer 4

No

Question 5

Are epigenetic markers permanent trhoughout the life? Why/Why not?

Answer 5

It’s often long term but not necessary permanent since it can be influenced by the environment, diseases etc. But it will remain through cell division.

Question 6

When an egg is fertilized what happens with the epigenetic markers?

Answer 6

The egg carries the maternal methylation pattern and the sperm the paternal methylation pattern. When the zygot is formed which is when the egg and sperm fuses they both have their methylation pattern. But trhougout cell divisions the paternal methylation pattern will through active demethylation drasticly go down while the maternal methylation pattern goes down gradually trhough passive demethylation.

Question 7

What happens with the methylation pattern at the morula stage?

Answer 7

The methylation pattern is basicly 0

Question 8

What happens at the blastocysts stage for the methylation pattern?

Answer 8

Denoval methylation is initiated which means that new methylation patterns are ninitated in the embreyo.

Question 9

What are the enzymes thar remove the maternal and paternal methylation pattern called?

Answer 9

TET

Question 10

Which enzyme make the new methylation patterns?

Answer 10

DNMT3b and DNMT3a

Question 11

Which enzyme maintains the methylation pattern trhough somatic cell divisions?

Answer 11

DNMT1

Question 12

When are the methylation pattern most sensitive to enviormental stimulus?

Answer 12

In the early embryiotic stages

Question 13

Which enzyme silence genes?

Answer 13

Methyltransferase, DRM2

Question 14

Which enzymes are responsible for cell differentation in early embryonic stages?

Answer 14

DNMT3a and DNMT3b

Question 15

What happens with the DNA during disease such as cancer?

Answer 15

The methylation pattern is disrupted. Silenced DNA is activated and activated DNA is silenced which disrupts the cell. There can be hypermethylation of important CpG islands that are important for tumor supressor genes which silence them.

Question 16

What are CPG islands?

Answer 16

Parts of the DNA with a high concentration of the dinucleotide CpG

Question 17

What are promotor CpG islands?

Answer 17

The CpG is often methylated and methylated CpG islands near the promotor part of the gene is important for gene regulation.

Question 18

What does DNMT do?

Answer 18

It takes a methylgroup from a molecule called SAM and adds it to the H on the nucleotide to make it a CH3.

Question 19

How does methylation on CpG happen?

Answer 19

DNMT flips the cytosine nucleotide up adds the methylgroup then flips it back down

Question 20

Which enzyme is respnsible for demethylation and how does it do it?

Answer 20

TET, it can add hydroxyl groups but also remove hydrogen so it can demethylate methylated cytosines.

Question 21

Which enzyme removes the maternal and paternal methylation pattern

Answer 21

TET

Question 22

When are the epigenetic markers rmeoved?

Answer 22

In the zygot stage and primordal germ cells that then involves in to egg and sperm cells

Question 23

What is genomic inprinting?

Answer 23

It’s when only one gene is active either the maternal or the paternal

Question 24

When are maternal and paternal genomic inprinting established?

Answer 24

Maternal inprinting is established postnatal and the paternal prenatal

Question 25

How does the genomic inprinting change during fertilization and embryonic developmeant?

Answer 25

It stays trhoughout demethylation but will be ereased in the primordal germ cells (embreyos)

Question 26

Which enzyme has usually mutated in cancer?

Answer 26

TET, they often mutated wich leads to methylation of tumor supressor genes

Question 27

Where does methylation occur?

Answer 27

Always at the fifth carbon in the cytosine

Question 28

How many procents of cytosine is methylated?

Answer 28

4%

Question 29

How many procent of CpG is methylated?

Answer 29

70-80%

Question 30

How many procent of CpG in CpG islands are methylated?

Answer 30

90% unmethylated

Question 31

How many procent of CpG in regular CpG sequences are methylated?

Answer 31

97% methylated

Question 32

Can methylation patterns be inherited?

Answer 32

Yes, the replication fork recognices the methylated sequences

Question 33

What are closed and open chromatin?

Answer 33

Open chromatin are open for trancription closed are to tightly packed and unavable

Question 34

What are hetero and euchromatin functions?

Answer 34

Hetero chromatin are tigthly packed in the middle of the nucleus, they are mostly closed and mostly silenced and has no function. Eucrhomatin has few histones, open and are responsible for constistutive and structural like centromers and telomers

Question 35

What are x-inactivation and where does it happen?

Answer 35

In somatic cells only one x chromosome is active chosen randomly, and it happens trhough 32-100 cell stages. In germ cells both x chromosomes are active.

Question 36

What does it mean when a cell is pluripotent?

Answer 36

It's a stem cell that can turn into any type of cell

Question 37

What does transcription factors do and where can they be found in early cell stages and what happens when the cell divides?

Answer 37

They turn on genes and they can be found in clusters in certain parts of the cell so when the cell divides some end up with the transcription factors and some end up without since the transcription factors where only in parts of the cell.

Question 38

What does asymmetric segregation of cellular determinants mean?

Answer 38

It's when the transcription factors form clusters and trhough cell division some cells end up with lots and some ends up with no transcription factors which leads to different parts of the genes turned on in different cells.

Question 39

What is induction?

Answer 39

When the cells through different types of cell communication influence each other to specialize into different cell types.

Question 40

Why is induction important?

Answer 40

It's to form lots of the same cells such as limbs, eyes etc.