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Sexual Genetics > Epigenetic effects; Genome imprinting > Flashcards

Epigenetic effects; Genome imprinting Flashcards

1
Q

Genomic Imprinting

A

expression of some genes depends on parental origin of the gene caused by different epigenetic modifications

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2
Q

Epigenetic

A

change in gene expression without change in DNA sequence

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3
Q

Parthenogenesis

A

form of asexual reproduction where development of embryos occurs without fertilization by a male, they develop from female cells

found naturally in some invertebrate animal species and some vertebrates (fish)

no known cases of naturally occuring mammalian parthenogenesisi in the wild

induced parthenogenesis in mice and monkeys results in malformation

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4
Q

Teratomas

A

3 germ layers
uniparental embryoes
maternal contribution

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5
Q

Hydatidiform moles

A

trophoboblasts
androgenetic constitution
the paternal contribution is important

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6
Q

imprinted genes influence

A

transfer of nutrients to the fetus and the newborn from the mother and affect growth in the womb and behaviour after birth

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7
Q

duplication on chromosome 7 results:

A

maternal duplication: small placenta and embryoo

paternal duplication: giant placenta and embryo

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8
Q

Prader Willi Syndrome causes

A

deletion on chromosome 15
Maternal uniparental disomy
wrong imprinting

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9
Q

Angelman Syndrome causes

A

deletion on chromosome 15
paternal uniparental disomy
wrong imprinitng

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10
Q

special of c15

A

identical genetic change may result different clinical phenotypes depending on the parental origin of alteration

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11
Q

Angelman Syndrome

A

Gene- UBE3A- ubiquitin ligase
in brain only maternal copy is active, paternal inactive

loss of maternal copy by maternal gene mutation, translocation, deletion, Paternal disomy

developmental delay, severe speech impairment, movement or balance disorder, hypermotoric behaviour, frequent laughter/ smilling
Puppet children

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12
Q

Prader-Willi syndrome

A 
gene- snoRNA (small nucleolar) and SNRPN
paternal copy is expressed
maternal copy is silenced
loss of paternal copy by paternal deletion, translocation, mutation
maternal disomy
hypotonia, obesity, hypogonadism
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13
Q

Whats needed for proper development in embryonic and later life

A

both maternal and paternal nuclear genomes

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14
Q

what is the difference between paternal and maternal genome?

A

Genomic imprinting

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15
Q

genomic imprinting

A

some nuclear genes of sperm and oocyte are modified differently

called epigenetic marks or genomic imprinting which results parental origin gene expresssion

majority of imprinted genes have role in control of embryonic growth, development, and development of placenta

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16
Q

usually genomic imprinting results in

A

monoallelic expression

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17
Q

imprinted genes are often clustered

A

good to know

18
Q

biallelic expression

A

when both paternally and maternally expressed

19
Q

what do some germ cell genes influence

A

growth and development that are differently modified (imprinted) and these genes show parental origin expression

20
Q

Mechanisms of imprinting/epigenetics

A

Transcription- DNA methylation and Histone modifications

Posttranscription- RNA mediated gene silencing

21
Q

imprinting/epigenetics- Transcription

A

Transcription- DNA methylation (CpG islands) DNMT1, 3A, 3B
CpG islands at promotors of genes are normally unmethylated, allowing transcription. Aberrant hypermethylation leads to transcriptional inactivation

Histone modifications (acetylation, methylation, phosphorylation, ubiquitination)- effects: activation, histone deposition, euchromatic, silencing, etc

22
Q

Histone code hypothesis

A

different combinations of covalent histone tail modifications may specify the transcription of a gene = histone code

together with other modifications such as DNA methylation it is part of the epigentic code

23
Q

histone modifcations:
erasing
writing
reading

A

erasing- demethylases, deacetylases and phosphatases

writing- methyltransferases, acetyltransferases, kinases, and ubiquitin ligases

reading- proteins with domains such as bromo, chromo, tudor

24
Q

H3 funtions

A

transcriptional competence- euchromatin

inhibition of transcription- heterochromatin

inhibition of transcription- facultative heterochromatin

25
Q

interaction of DNA and histone modifications (1)

A

DNA methylation induces hisstone de-acetylation

MeCP2 binds methylated DNA –> then recruits HDAC –> which de-Acetylates histones (heterochromatin/repressed euchroamtin)

26
Q

interation of DNA and histone modifications (2)

A

histone H3-K9 methylation induces DNA methylation

HP1 targets methyl H3-K9 –> then recruits DNMT –> which methylates DNA

27
Q

imprinted domain of maternal 15th chromosome

A

DNA cytosine methylation
Histone H3 tail methylation at lysine (H3-K9)
histone deacetylating enzymes – histone deacetylation

inactive chromatin

maternally expressed UBE3A

28
Q

Imprinted domain of paternal 15th chromosome

A

no DNA cytosdine 5- methylation

histone H3 is lysine 4- methylation (H3-K4me)
histone acetyltransferase (HAT)
and H4 is acetyulated

active chromatin

paternally expressed SNRPN and antisene UBE3A

29
Q

main genomic imprinting mechanisms (influencing expression)

A

DNA methylation
histone modifications
RNA interference

30
Q

Beckwith- Wiedemann syndrome

A 
overgrowth disorder
increased risk of childhood cancer 
macroglossia (large tounge)
macrosomia (higher birth weight and lenght)
midline abdominal wall defects
ear creases or ear pits 
neonatal hypoglycemia

location: 11p15

genes: IGF2 (paternal expression)
H19 (maternal expression-noncoding RNA)
hypermethylated maternal ICR1
paternal disomy and other mutations may cause this disroder

31
Q

silver russel syndrome

A

RSS
opposite growth disroder- dwarfism
maternal disomy
hypomethylated paternal ICR1

32
Q

IGF2

A

insulin like growth facotr 2
major fetal growth factor
paternally expressed

33
Q

H19 non coding RNA

A

mainly prenatally

maternally expressed oncogene

34
Q

Rett syndrome

A

progressive neurodegenerative disroder
XD
male lethality
characteristic hand wringing

mainly cuased by mutation of MeCP2 (Methyl-cPG-bindign protein) so there is no inhibition of transcription

35
Q

Fragile X syndrome

A

XD with incomplete penetrance

CGG repeats
FMR-1 
fragile x mental retardation protein 
normal: 5-55 CGGS
premutation: 55-200 CGGs
full mutation: over 200 CGGS
36
Q

uncorrect imprinting may cause

A

diseases

duh.

37
Q

how is genomic imprinting established

A

somatic cells have to retain epigenetic marks

germ cells ahve to become epigenetically different from somatic cells (erase and reprogramming)

38
Q

maintance of parental marks through somatic cell division

A

DNMT1- maintenance

DNMT3a,b de novo

39
Q

genetic imprinting needs different mechanisms in somatic (retained) and germ cells (erased and sex-dependently reprogrammed)

A

ok

40
Q

conflict hypothesis

A

maternal imprinting: limits use of maternal resources by baby in utero
less growh
down regulates growth factors

paternal imprining
maximizes use of maternal resources by baby in utero
more growth
down regulates suppressive factors

IgF2 (growth stimulation)

41
Q

possible significance of genomic imprinting

A

mothers gene keeps mothers power in store for forthcoming offsprings

fatehrs genes use up mothers power to ensure their transmission

42
Q

assisted reproductive technologies

A

in vitro fertilization
intra-cytoplasmic sperm injection
ooplasm donation

could disrupt the correct maintenance of imprinting, may be associated with imprinting defects

Sexual Genetics (10 decks)

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