Flashcards in Genomic imprinting and epigenetics Deck (38):
development dependent on father
development dependent on mother.
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.
are hydrotidiform mole androgenic or pathogenic`
what is the composition of a Hydatidiform mole
Proliferation of abnormal trophoblast tissue.
Can develop into malignant trophoblastic tumour
which structure hyperprolifearates in hydatidiform mole
what teratoma is caused by parthenogenesis
what are benign ovarian teratomas derived from
oocytes which have completed first or both meiotic divisions
why do pathogenic embryos dies
failure of development of extra embryonic structures
trophoblast and yolk sac.
what structures are present in patharthogenic tumours and what structures are not.
– Predominantly epithelial
– No skeletal muscle
– No membranes/placenta
at what month do androgenetic embryos typically die
-- 6 month stage
what does uniparental conceptions fail
maternal and paternal genes have different structures.
gene dosage is not normal
karyotyping is not normal.
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.
where is genomic imprinting encoded because it is not in the DNA nucleotides
what factor does genomic imprinting rely on
modifications in gametogenesis
spermatogenesis and oogenesis.
what are the common clinical signs of angelman syndrome
facial dysmorphism- proganthisms, wide mouth and drooling.
Mental handicap- microcephaly and absent speech.
Ataxic jerky movements
Hand jerks up and down.
what are the common clinical signs of Prader- will syndrome
Infantile hypotonia-Feeding problems, Gross motor delay.
Low muscle tone- floppy
Small hands and feet
In which chromosome do abnormalities in angel man and order willis arise due to
lack of maternal DNA on chromosome 15 causes which condition.
lack of paternal DNA on chromosome 15 causes which condition.
At what bases dinucleotide does demythylation occur
what enzyme carries out DNA methylation
which areas are spared of DNA methylation
promoter regions spared: CG “islands”
what effect does methylating a CpG island have.
inactivate the promoter region gene and hence the translocation as well.
what is the function of DNA methylation
example of a condition caused by imprinting problems
Beck with wiedenmann syndrome
what is the pathogenesis behind beck with- wiedmann syndrome
hyper methylation causing increased insulin like growth factor 2 which is a major growth promoter
clinical symptoms of beck with- wiedmann syndrome.
what is the pathogenesis behind Russell-Silver syndrome
hypomethylation causing decreased insulin like growth factor 2 which is a major growth promoter
what are the clinical symptoms of russell silver syndrome
• Growth retardation
– Fetal (IUGR)
– Persistent postnatal growth failure
• Triangular face
– Brain size more preserved
• Sporadic occurrence
when does imprinting take place
X chromosome is larger than the Y so do males of females have a larger amount of DNA content.
when must genetic imprinting be remembered and when must it be forgotten
remember in somatic cell division
forget in gametogenesis.
what process takes place to silence a full X chromosome in females
X inactivation or lyonisation.
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
what test is used for the Hypohidrotic ectodermal dysplasia.
– Starch/iodine test
– Patches of skin with or without sweat glands
what is Hypohidrotic ectodermal dysplasia and what inheritance is it.
sweat glands have a abnormal distribution.