L16-Imprinting

Question 1

what is genetic imprinting?

Answer 1

its where some genes are expressed only from the maternal OR the paternal side
occurs during gametogenesis

Question 2

at which base of the DNA does methylation occur? and where are they normally located

Answer 2

Cytosine

at CpG islands, next to a guanine using methyltransferase

Question 3

what is the result of DNA methylation V histone methylation?

Answer 3

DNA methylation = condensed DNA = silenced

histone mehtylation = uncoiling = active

Question 4

how does DNA methylation replicate during replication?

Answer 4

the enzyme Dnmt1 is essential and puts on DNA methylation to exactly the same copy parental strand
Dnmt3 a and b put on new DNA METHYLATION

Question 5

which parental genome Is faster at demethylation of DNA at the zygote stage?

Answer 5

paternal genome is faster

Question 6

describe how genetic imprinting/ functional haploidy occurs and give an example?

Answer 6

e.g Igf2 and H19 genes
igf2 - insulin gf which is paternally expressed
H19 - non coding RNA which is maternally expressed
Igf2 ON: - DAD DNA
- dmr1 and 2 need to be all methylated and the DNA level =
- as dmr1 is inactivated by methylation,
whereas dmr2 is activated by methylation = causes IGF2 to be transcribed

H19 ON: - MOM DNA
- CRCF inhibits H19 expression, as DMR binds to it
this also silences DMR1 and 2
=IGF2 is silenced