Genomic imprinting and epigenetics Flashcards Preview

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Flashcards in Genomic imprinting and epigenetics Deck (38):
1

define androgenesis

development dependent on father

2

define parthenogenesis

development dependent on mother.

3

when are the 2 polar bodies pouched out of the egg

1st- pushed out meiotic division 1.
2nd pushed out- after meiotic division 2 which gives rise to the diploid composition.

4

are hydrotidiform mole androgenic or pathogenic`

androgenic

5

what is the composition of a Hydatidiform mole

homozygous 46,XX
Proliferation of abnormal trophoblast tissue.
Can develop into malignant trophoblastic tumour
No embryo

6

which structure hyperprolifearates in hydatidiform mole

trophoblast.

7

what teratoma is caused by parthenogenesis

beningn ovarian

8

what are benign ovarian teratomas derived from

oocytes which have completed first or both meiotic divisions

9

why do pathogenic embryos dies

failure of development of extra embryonic structures
trophoblast and yolk sac.

10

what structures are present in patharthogenic tumours and what structures are not.

– Predominantly epithelial
– No skeletal muscle
– No membranes/placenta

11

at what month do androgenetic embryos typically die

-- 6 month stage

12

what does uniparental conceptions fail

maternal and paternal genes have different structures.
gene dosage is not normal
karyotyping is not normal.

13

define genomic imprinting.

A mechanism that ensures the functional non-equivalence of the maternal and paternal genomes.
if a patronal gene is imprinted it is silenced and only the maternal gene is expressed.

14

where is genomic imprinting encoded because it is not in the DNA nucleotides

epignetics

15

what factor does genomic imprinting rely on

modifications in gametogenesis
spermatogenesis and oogenesis.

16

what are the common clinical signs of angelman syndrome

facial dysmorphism- proganthisms, wide mouth and drooling.
Mental handicap- microcephaly and absent speech.
Seizure disorder
Ataxic jerky movements
Hand jerks up and down.

17

what are the common clinical signs of Prader- will syndrome

Infantile hypotonia-Feeding problems, Gross motor delay.
Mental handicap
Low muscle tone- floppy
Male hypogenitalism/
cryptorchidism
Small hands and feet
Hyperphagia- Obesity
Stereotypic behaviour

18

In which chromosome do abnormalities in angel man and order willis arise due to

chromosome 15

19

lack of maternal DNA on chromosome 15 causes which condition.

angelman

20

lack of paternal DNA on chromosome 15 causes which condition.

Prader willis

21

At what bases dinucleotide does demythylation occur

CG

22

what enzyme carries out DNA methylation

DNA methyltransferase.

23

which areas are spared of DNA methylation

promoter regions spared: CG “islands”

24

what effect does methylating a CpG island have.

inactivate the promoter region gene and hence the translocation as well.

25

what is the function of DNA methylation

gene regulation.

26

example of a condition caused by imprinting problems

Beck with wiedenmann syndrome

27

what is the pathogenesis behind beck with- wiedmann syndrome

hyper methylation causing increased insulin like growth factor 2 which is a major growth promoter

28

clinical symptoms of beck with- wiedmann syndrome.

foetal overgrowth
organomegaly- exomphalos
hypoglycaemia
asymmetry
tumour risk

29

what is the pathogenesis behind Russell-Silver syndrome

hypomethylation causing decreased insulin like growth factor 2 which is a major growth promoter

30

what are the clinical symptoms of russell silver syndrome

• Growth retardation
– Fetal (IUGR)
– Persistent postnatal growth failure
• Triangular face
– Brain size more preserved
• Asymmetry
• Sporadic occurrence

31

when does imprinting take place

gametogenesis.

32

X chromosome is larger than the Y so do males of females have a larger amount of DNA content.

females.

33

when must genetic imprinting be remembered and when must it be forgotten

remember in somatic cell division
forget in gametogenesis.

34

what process takes place to silence a full X chromosome in females

X inactivation or lyonisation.

35

what is the difference between imprinting and X lionisation

– Whole X chromosome is silenced
– Random choice of parental chromosome
– Different in different cells
– Somatic cell clones “remember”
– Occurs early in embryogenesis
– Blastocyst

36

what test is used for the Hypohidrotic ectodermal dysplasia.

– Starch/iodine test
– Patches of skin with or without sweat glands

37

what is Hypohidrotic ectodermal dysplasia and what inheritance is it.

X-linked mutation
sweat glands have a abnormal distribution.

38

random skewing in X inactivation- what problems can this cause

Increase the number of X linked mutation is females if the normal gene is switched of and the other gene remains on.