Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Human reproduction and fertility > Alvey > Flashcards

Alvey Flashcards

1
Q

What was shown in experiments in mice in 1984?

A

Both paternal and maternal genes are essential for embryo development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are Gynogenetic diploids?

A

Injection of two female (haploid) pronuclei into a mouse egg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are Androgenetic diploids?

A

Injection of two male (haploid) pronuclei into a mouse egg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what happened to the gynogenetic and androgenetic diploids?

A

a normal embryo did not develop in either case

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why did the authors conclude this was not due to the sex chromosomes?

A

even the XX individuals did not survive

It was down to genomic imprinting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the IGF-II signal controlled?

A

From paternal side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is the IGF-II receptor controlled?

A

from the maternal side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does Targeted disruption of the insulin-like growth factor II gene result in?

A

growth-deficient (small) mice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Female WT x Male heterozygote:

A
  • Some healthy males and females
  • Some small males and females (heterozygotes)
  • Phenotype depends on the paternal allele they got
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Male WT x female heterozygote:

A
  • All offspring are phenotypically normal

* Heterozygotes of both sexes are not affected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What were the conclusions from the IGF-II imprinting paper?

A
  • Transmission of the IGF-II mutation through the male germline results in heterozygous progeny that are growth deficient.
  • The difference in growth phenotypes depends on the type of gamete contributing the mutated allele.
  • Homozyous mutants are indistinguishable in appearance from growth-deficient heterozygous siblings
  • Only the paternal allele is expressed in embryos, while the maternal allele is silent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is maternal imprinting?

A
  • Allele of a particular gene inherited from the mother is transcriptionally silent (not expressed!)
  • Direct observation of the phenotype governed by the paternal allele
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is paternal imprinting?

A
  • Allele of a particular gene inherited from the father is transcriptionally silent (not expressed)
  • Direct observation of the phenotype governed by the maternal allele
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What usually happens if there is a defective copy of a gene inherited?

A

there is a second (functioning) copy from the other parent that can compensate for this loss
not true of imprinted genes and results in disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is OMIM?

A

Online Mendelian Inheritance in man
It is a database for genetic diseases in humans
It is a respected source by the academic community
It is free and easy-to-understand.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the clinical phenotype of Beckwith-Wiedemann

Syndrome?

A

Large birth size,

Pre-disposition to tumours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is Beckwith-Wiedemann

Syndrome caused?

A

11p15.5 (paternal)
(contains IGF-II homologue)
Hypomethylation ICR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the clinical phenotype of Prader-Willi Syndrome?

A

Obesity, behaviour and cognitive problems, deficiencies in sexual development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How is Prader-Willi Syndrome caused?

A

15q11-q13 (paternal)
PW region deletion (70% cases)
Maternal uniparental disomy (25% cases)
Mutations in the imprinting control region (ICR)
Translocation that separates the ICR from the Prader Willi region

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the clinical phenotype of Angelman Syndrome?

A

Developmental deficiencies, sleep disorders, seizures, happy disposition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How is Angelman Syndrome caused?

A

15q11-q13 (maternal)
Deletion of PW region(70% cases)
Mutation of UBE3a (10%)
Paternal uniparental disomy (3%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the clinical phenotype of Silver russell syndrome?

A 
Growth retardation -small
triangular face
growth assymettry
immature bone development
excessive sweating
cardiac defects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is Silver russell syndrome caused?

A 
Chromosomes 7, 8, 15, 17, 18
maternal UPD
Maternal duplication of 11p15
hypomethylation of 11p15
defects in 7p11.2 and p13
encodes the GRB10 gene required for growth and development
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What maintains and active chromatin state?

A

Histone acetyltransferase (HAT) targets H3 tail.
H3K14ac is a docking site for Bromo-domain
proteins;
stimulates nucleosome accessibility
Reversed by histone de-acetylases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What maintains a repressed chromatin state?

A

Histone lysine methyltransferases (KMT) methylates H3 tail.
H3K9me3 provides docking site for heterochomatin protein 1 (HP1)
Impairs nucleosome accessibility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What methylation state at CpG islands maintains an active state?

A

demethylation

27
Q

What methylation state at CpG islands maintains a repressed state?

A

methylated

28
Q

How often does epigenetic reprogramming occur in development and when?

A
  1. During gamete formation

2. Post-fertilisation

29
Q

What is reprogramming?

A

erasing and adding the epigenetic marks

30
Q

What happens to imprinted genes during development?

A
  • Imprinted genes always exhibit the methylation pattern of the parent in sperm or eggs regardless of whether they came from the maternal or paternal genome
  • Imprinted genes bypass epigenetic reprogramming in the early embryo – not known how
31
Q

What epigenetic marks would an egg have?

A

egg has no paternal marks only maternal

32
Q

Stages of the mammalian Life Cycle

A
  • Primordial germline cells (PGCs) are specified during early embryonic development
  • PGCs migrate to the (developing) gonads
  • Meiosis
  • Gamete differentiation
  • Fertilization of oocyte by sperm
  • Totipotent zygote formation
  • Primordial germline cells are specified
33
Q

What is the purpose of genome wide epigenetic reprogramming in gamete fromation?

A
  1. Re-sets imprinted genes for the sex of the embryo
  2. Erases parental of acquired epigenetic memories (e.g. environmental)
  3. Facilitates gametogenesis
  4. Maintain the silencing of transposable elements
  5. Reduces the mutation rate in the germline
34
Q

What is the purpose of genome wide epigenetic reprogramming in the pre-implantation embyo?

A
  1. Re-sets zygotic epigenetic genome for naïve pluripotency

2. Some evidence of maternal vs paternal genome wars

35
Q

How is epigenetic memory erased?

A

Somatic epigenetic memories are erased by:

  1. Global DNA demethylation
  2. Genomic imprint erasure
  3. X-chromosome reactivation
  4. Reorganisation of chromosome
36
Q

What is the DNA methylation profile in the germline?

A

Migratory primordial germ cells (PGCs) become demethylated in early development.

Remethylation begins in spermatogonial stem cells (SSCs) in males

Remethylation begins after birth in growing oocytes

37
Q

How does genome wide DNA demethylation occur?

A
  • DNA is hypermethylated (70%) and the PGCs are primed for differentiation.
  • At the onset of migration, PMCs undergo genome-wide demethylation (to 4%)
  • Almost all genomic features (including imprint control elements) become hypomethylated (little methylation)
  • This is thought to act mostly via a passive mechanism
38
Q

When is methylation re-established in male mice?

A

after E13.5 in males

39
Q

When is methylation re-established in females mice?

A

after birth in females

40
Q

What percentage of genoic loci remain methylated in PGCs after demethylation?

A

4%

41
Q

What are the majority of ascapees associated with

A

retrotransposable elements

42
Q

How do loci escape demethylation?

A
  • The mechanism is not known

* The current assumption is that it is due to incomplete repression of DNA methylation pathway – but that’s a best guess

43
Q

How is DNA demethylation essential for imprint erasure?

A

Allele-specific methylation at imprinting control regions (ICRs) are erased in PGCs

Re-established in a sex-specific manner later in development.

44
Q

What’s happening in male gametes to the (imprinted) IGFR2 locus?

A

In male ES cells both copies of Igf2r are unmethylated

45
Q

What is occuring in the pre-implantation embryos in epigenetic resetting?

A

Immediately following fertilization the paternal genome is demethylated by an active mechanism
The female genome is demethylated by a passive mechanism that requires DNA replication

46
Q

how do methylated imprinted genes remain that way?

A

Methylated imprinted genes to not become demethylated

47
Q

how do demethylated imprinted genes remain that way?

A

Unmethylated imprinted genes to not become re- methylated

48
Q

What are the waves of demethylation and re-methylation in the early embryo essential for ?

A

normal development and establishing totipotency

49
Q

post-fertilisation, how are paternal and maternal imprints maintained in the developing zygote?

A
  • When the male pronucleus enters the oocyte (nearly) all methylation is actively removed from the paternal genome.
  • The mechanism by which some genes bypass the reprogramming is not known, but long non-coding RNAs are a candidate mechanism
  • Whatever the mechanism, parent-of-origin specific DNA methylation is transmitted at imprinted loci. Imprints must be maintained during global DNA methylation in the pre-implantation embryo and persist in somatic cells
50
Q

What are the Implications for treating imprinting disorders?

A
  • Imprinting genes are silenced using normal epigenetic machinery of the cell
  • This machinery is restricted to just one allele in the developing gamete
  • Is this ‘mechanism of restriction’ is understood, it may be possible to develop therapies for imprinting disorders (e.g. PWS)
  • Reactivate the expression of silent parental alleles to reduce symptoms.
51
Q

Describe a mechanism that has been suggested to protect imprinted genes the waves of genomic reprogramming in the developing embryo?

A

Both cis and trans acting factors are involved
DNA binding factors recognise ICRs and prevent active demethylation
e.g. MBD3 likely as part of a complex
e.g. ZFP57 by recruiting a corepressor

52
Q

Name an enzyme responsible for establishing imprinting marks

A

DNA methyltransferase

DNMT3L stimulatory protein

53
Q

What are imprinted loci a barrier to?

A
  • Cloning Mammals
  • Generation of oocytes in vitro
  • The production of bimaternal and bipaternal mammals
  • The generation of artificial gametes from somatic tissue
54
Q

How was dolly made?

A

somatic cell nuclear transfer

55
Q

Was dolly a normal sheep?

A
  • She was fertile

* She died young (lung cancer)

56
Q

Why was dolly not a normal sheep?

A

• There was no re-setting of epigenetic marks – had a mature diploid oocyte with all the epigenetic marks of a differentiated cell

57
Q

Why is it an issue if the epigenetic state has not been reset?

A
  1. Cell is not pluripotent
    • Assumed that it became demethylated in a gradual, delayed and nonspecific manner
  2. The epigenetic marks had been copied many times by and error prone manner (1 in 25)
    • Cell used already had many epigenetic mutations from its lifetime
58
Q

how could Artificial Gametes be used 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 partner’s egg or sperm
  6. Develop into embryo
  7. Implant into mother
59
Q

What are man made mature oocytes made from?

A
  1. Embryonic stem cells
  2. Induced stem cells
    o Embryonic fibroblasts
    o Adult tail tip fibroblasts
60
Q

How were eggs made from PGCs and was this effective?

A

primordial germ-cell-like cells are co-cultured with female gonadal somatic cells, and hormones, inhibitors and other factors are administered at key stages to stimulate the development of a follicular environment and to coordinate stages of the egg cell’s maturation
3.5% made pups
Imprints are sufficiently maintained to generate fertile mice (both male and female)

61
Q

How have bimaternal mice been generated?

A

• Started with an active ooycyte
• Isolated haploid ESCs and cultured
• Counted how many passages to remove methylation (20 – 24)
o Non-specific – can lead to errors
o Continued until 4%
• Used CRISPR to delete imprinted regions (not gene deletions)
• Deletion of different regions gave different phenotypes
• With three deletions got an almost normal mouse
o These are the barriers to bi-maternal reproduction

62
Q

How have bipaternal mice been generated?

A
  • Had to culture for 40 passages to lose methylation pattern
  • Systematically deleted maternally imprinted regions
  • Deletions of up to 6 regions cause death
  • Deletion of seventh gene allowed pups to survive for 48 hours – not fertile
  • Injected with a sperm into an enucleated oocyte
  • Think there are hundreds of imprinted regions so would have to knockout many more regions to have a phenotypically normal mouse
63
Q

What is the impact of bimaternal and paternal mice on imprinting disorders?

A
  • Could be used to model the 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 imprinted genes might offer an approach to treat imprinting disorders
64
Q

In Vitro differentiation of iPSCs

A

iPSC = induced pluripotent stem cell
• no ethical issues
• no immune rejection
• abundant source
• can be obtained from azoospermia patients
iPSCs were differentiated into PGCLCs in culture (in vitro)
Grafted under the bursa
Formed mature artificial oocytes under in vivo like conditions
As PGCs were formed in vitro the methylation status is likely abnormal

Human reproduction and fertility (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions