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human reproduction and fertility > alvey > Flashcards

alvey Flashcards

1
Q

generally paternal alleles want offspring to be what?

A

big

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2
Q

generally maternal alleles want offspring to be what

A

equal size and manageable

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3
Q

how was it shown that both maternal and paternal genes are essential for embryo development

A

gynogenetic diploid were inviable and androgenetic diploids were inviable

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4
Q

as even the XX individuals did not survive what could the authors conclude

A

that inviability was not caused by the sex chromosomes

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5
Q

imprinting is essential for normal development in mammals T/F

A

T

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6
Q

Imprinting is important for development of what animals

A

development of long lived animals with placenta

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7
Q

what is a classic example of an imprinted gene

A

IGF-II

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8
Q

what is IGF-II

A

insulin like growth factor II gene

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9
Q

what kind of imprinting does IGF-II go under

A

maternal imprinting

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10
Q

if IGF-II is knocked out what size mice

A

small mice

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11
Q

when the IGF-II mutation is transmitted through which germline does it result in heterozygous progeny that are growth deficient

A

male

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12
Q
  • When the disrupted IGF-2 gene is transmitted maternally, the heterozygous off-spring are
A

phenotypically normal

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13
Q

how was it concluded that inheritance of Igf-2 and phenotpye was not a dosage effect

A

Homozyous mutants are indistinguishable in appearance from growth-deficient heterozygous siblings

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14
Q

in mice the paternal and maternal members of some autosomal gene pairs are functionally…

A

non equivalent

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15
Q
  • Only the paternal allele of IGF-2 is expressed in embryos, while the maternal allele is silent
A

T

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16
Q

what is maternal imprinting

A

allele of a particular gene inherited from mother is transcriptionally silent (not expressed
direct observation of phenotype is governed by paternal allele

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17
Q

what is paternal imprinting

A

allele of a particular gene inherited from father is transcriptionally silent
direct observation of the phenotype is governed by maternal allele

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18
Q

usually in diploid species, if a defective copy of a gene is inherited there is a second functioning copy from the other parent that can compensate for this loss. what is this not true for

A

imprinted genes

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19
Q

in imprinted genes - Even though there are two copies of the gene, as only one copy is expressed, mutations affecting this copy will result in disease. T/F

A

T

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20
Q
  • Situations that result in both copies of a gene being silenced will also lead to expression of the disease. this is known as …
A

uniparental disomy (UPD)

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21
Q
  • An imprinted region of the human genome that contains Ifg2 (the human homologue of IGF-II mouse gene) causes a paternally inherited disease called what
A

Beckwith-Weidemann syndrome

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22
Q

what is beckwith weidemann syndrome?

A

pediatric overgrowth disorder involving a predisposition to tumour development

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23
Q
  1. mutation in dad germline results in hypermethylation of IC1
  2. daughter now has active copy of IGFR2 from dad. the maternal copy is silenced
  3. has child that has active copies from both parents so has BWS
A

T

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24
Q

what is prader willi syndrome characterised by

A

obesity, behaviour and cognitive problems. deficiencies in sexual development

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25
Q

in the gene that causes preader willi and angelmans which copy of the gene normally gets expressed and which is normally silenced

A

dad -expressed

mums - silent

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26
Q

what happens in prader willi syndrome

A

paternal gene doesnt get expressed so no forms of the gene are expressed

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27
Q

how is the paternal gene not expressed in prader willi

A 
deletion of PW genes
maternal UPD (silent)
mutation in imprinting centre leading to methylation of paternal gene
epimutation - wrong methylation (not erased from mother)
translocation to move the genes away from imprinting centre
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28
Q

which gene causes angelmans syndrome and where is it usually expressed

A

UBE3A - only expressed on maternal

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29
Q

paternal mutations in chromsome 15 lead to what

A

prader willi

30
Q

maternal mutations in chromosome 15 leads to what

A

angelmans

31
Q

what can angelmans syndrome be caused by

A

maternal deletion of praderwilli region
mutation of UBE3A
UPD (father)

32
Q

what are the symptoms of angelmans

A

developmental deficiencies
sleep disorders
seizures
happy diposition

33
Q

what are the symptoms of temple syndrome

A

small stature
developmental delay
small hands and feet
central obesity developing with age.

34
Q

what imprinted region is involved in temple syndrome

A

14q32

35
Q

what causes temple syndrome

A

UPD - maternal
deletion of region
mutation in imprinting region

36
Q

when can UPD occur

A

after trisomy rescue due to a nondisjunction event

37
Q

what enzyme is involved with marking euchromatin

A

histone acetyl transferase - targets H3 tail. this is then a docking site for bromo-domain proteins which stimulate nucleosome assembly

38
Q

which enzymes are involved in repressing chromatin

A

histone lysine methyltransferases - methylate the H3 tail and provides docking site for heterochromatin protein 1 (HP1). this impairs nucleosome accessibility

39
Q

demethylation of CpG islands at promoter sequences is associated with what?

A

active genes

40
Q

methylation at CpG islands is associated with what?

A

silencing of the gene

41
Q

at a maternally imprinted locus, the promoter would be …

A

methylated

42
Q

the entire genome is methylated and demethylated how many times during gamete development and fertilisation

A

2 once during gamete development and once after fertilisation

43
Q

imprinted genes always exhibit the methylation pattern of the parent in eggs and sperm regardless of whether they came from maternal or paternal genome. resetting is done when?

A

primordial germ cell to gametes stage

44
Q

imprinted genes are reset in the developing gamete and bypass the epigenetic reprogramming when

A

in early embryo

45
Q

what is the purpose of genome wide epigenetic reprogramming in gamete

A

reset imprinted 1.genes for sex of embryo

  1. erases parental or acquired epigenetic memories
  2. facilitates gametogenesis
  3. maintain the silencing of transposable elements
  4. reduces mutation rate in germline
46
Q

what is the purpose of genome wide epigenetic reprogramming in pre-implantation embryo (2)

A

resets zygotic epigenetic genome for naive pluripotency

some evidence of maternal vs paternal wars

47
Q

during gamete formation imprinting genes change their status. in preimplantation embryo imprinted genes….

A

are protected

48
Q

imprinted genes act like the rest of the genome in gamete formation. Do not act like the rest of the genome in pre-implantation embryo T/F

A

T

49
Q

during migration of PGCs somatic epigenetic memories are erased by what techniques

A
  • global DNA demethylation
  • genomic imprint erasure
  • X-chromosome reactivation
  • reorganisation of chromosome
50
Q

remethylation occurs first in males/females

A

males

51
Q

remethylation begins when in males

A

spermatogonial stem cells E13.5

52
Q

remethylation begins when in growing oocytes

A

after birth

53
Q

vast majority of ecapees from global demethylation are associated with what

A

retrotransposable elements

54
Q

in preimplantation embryos the paternal genome is demethylated by what kind of mechanism

A

active mechanism

55
Q

in preimplantation embryos the female genome is demethylated by what kind of mechanism

A

passive mechanism that requires DNA replication

56
Q

the waves of demethylation and remethylation in the early embryo are essential for what

A

normal development and totipotency

57
Q
  • The mechanism by which some genes bypass the reprogramming is not known, but …… are a candidate mechanism
A

long noncoding RNAs

58
Q

When does genome-wide demethylation occur during mammalian

development?

A

in gamete formation (primordial germ cells) and in preimplantation embryos

59
Q

What would happen to an imprinted gene (e.g. UBE3 (causes

Angelman’s syndrome)) in the germline?

A

demethylated and maybe remethylated. reprogrammed

60
Q

which enzyme carries out reacquisation of methylation

A

DNA methyltransferase

3A (DNMT3A)

61
Q

what maintains methylation status

A

imprinted genes carry multiple motifs of 6 to 7 nucleotides (TGCCGC exactly), which will recruit a specific protein called ZFP57 only when this motif is methylated

62
Q

how does ZFP57 maintain methylation status

A

Through its KRAB domain, ZFP57 brings its cofactor KAP1 to the chromatin, which in turn leads to the recruitment of repressive chromatin modifiers, including ESET/SETB1, which controls H3K9 trimethylation
mutations in ZFP57 causes hypomethylation at multiple imprinted loci

63
Q

what are imprinted loci a barrier to (4)

A

cloning mammals
engineering reproductive cells
production of bimaternal and bipaternal mammals
generation of artificial gametes from somatic tissues

64
Q

what was the first cloned mammal and how was the procedure carried out

A

Dolly the sheep

somatic cell nuclear transfer

65
Q

what was the problem with dolly the sheep

A

there was no opportunity for resetting of methylation so the cell was not pluripotent
marks have been copied many times and copying of epigenetic marks is error prone

66
Q

what are the steps to artificial gametes as a fertility treatment

A
  1. take somatic cell
  2. perform SCNT and induce embryo development in vitro
  3. extract embryonic stem cells from blastocyst
  4. induce gametogenesis in vitro
  5. use functional gamete to fertilise partners egg or sperm
  6. develop into embryo
  7. implant in mother
67
Q

what were the man made mouse eggs made from

A
  1. embryonic stem cells

2. adult tail tip fibroblast

68
Q

how do you make a man made mouse egg

A
  • Fully in vitro method, primordial germ cell like cells are co-cultured with female gonadal somatic cells and hormones, inhibitors and other factors are administrated at key stages to stimulate the development of a follicular environment and to coordinate stages of egg cells maturation
69
Q

how did they make bimaternal mice

A

oocyte activation and isolation of haploid ESCs
loss of maternal imprints in culture
genome editing of paternally imprinted regions - deleted 3 ICRs
injection of the haploid ESC into a mature oocyte

70
Q

how did they make bipaternal mice

A

sperm injected into an enucleated oocyte
isolation of androgenetic haploid ESCs
loss of paternal imprints in culture
genome editing of maternally imprinted region - deleted 7 ICRs
coinkection of haploid ESC and sperm into an enucleated oocyte

71
Q

it is thought that there is about how many imprinted loci in the mouse genome

A

100

72
Q

what is the impact of the work of bipaternal/bimaternal mice in imprinting disoeders

A
  • Could be used to model regulation of imprinting genes
  • A technique for accurate reversible epigenetic switch between maternal and paternal imprinting
  • Offspring from same sex parents
  • Explore the feasibility of altering the regulation of imprinting genes might offer an approach to treat imprinting disorders

human reproduction and fertility (3 decks)

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