genetics Flashcards

1
Q

how do you do a DNA test on baby in utero?

A

take tissue from-
placenta = chorionic villus biopsy
skin/urine ells = amniocentesis
also fetal DNA from maternal serum

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2
Q

describe confined placental mosaicism

A

placenta has abnormal number of chromosomes but foetus does not e.g. can have trisomy 21 but baby doesn’t

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3
Q

what can you look for in invasive foetal testing?

A

chromosome abnormalities using micorarray
single gene changes using PCR/sequencing, NGS

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4
Q

what are the pros and cons of chromosome microarray?

A

pros- high resolution, technically easier, quick
cons- finds polymorphisms, can make incidental findings

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5
Q

when do you use chromosome microarray?

A

high risk of chromosomal trisomy
foetal abnormality on screening
parent has balanced chromosomal rearrangement

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6
Q

what are the differential diagnoses of a floppy baby?

A

Central(most common)
Hypoxic ischaemic encephalopathy
Intracranial haemorrhage
Cerebral malformations
Chromosomal abnormalities (e.g.Trisomy 21, Prader-Willi syndrome)
Congenital infections (TORCH)
Acquired infections
Peroxisomal disorders
Drug effects (e.g. benzodiazepines)

also abnormalities in Spinal cord, anterior horn cell, neuromuscular junction, muscle, peripheral nerves or metabolic myopathies

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7
Q

what are the next steps when you have a floppy baby?

A

do bloods (genetic, metabolic, infection, CK), imaging (cranial USS & MRI), neurology review, neurology review, early intervention & regular review

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8
Q

what things do you test floppy babies for rapidly?

A

myotonic dystrophy, PWS, spinal muscular atrophy

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9
Q

what is hypochondroplasia?

A

form of skeletal dysplasia less severe than achondroplasia
caused by specific activating mutations in FGFR3 gene
causes short stature and can cause temporal lobe epilepsy

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10
Q

what is is russell silver syndrome?

A

growth disorder characterised by slow growth before and after birth
can cause ‘elfin features’
poor weight gain

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11
Q

what causes russell silver syndrome?

A

abnormality of gene methylation

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12
Q

what is the treatment for russell silver syndrome?

A

growth hormone

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13
Q

when is growth hormone recommended?

A

small for gestational age without catch up growth by the age of 4
(growth hormone deficiency, turners syndrome, russell silver etc. also PWS)

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14
Q

why would you give growth hormone in PWS?

A

to help with muscle tone and encourage exercise to prevent T2DM

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15
Q

what happens when x chromosome forms a ring?

A

produces similar symptoms to turner’s syndrome- treat as such
investigations: IGF1, TFTs, coeliac screen, bone age x-ray
treatment: growth hormone, puberty induction, renal & cardiac follow up, bp monitoring, annual bloods, thyroid and coeliac screening

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16
Q

what is bardet biedl syndrome?

A

extremely rare genetic condition causing visual impairment, renal abnormalities, polydactyly, learning difficulties, hypogonadism, hyperphagia and obesity