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Flashcards in genetics and syndromes Deck (47):
1

genetics downs

trisomy 21

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features downs

hypotonic, flat occiput, single palmar crease, uncurved fifth finger, wide sandal gap between big and second gap

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what % have congenital heart disease in downs

30%

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what % downs patients live to >50

50%

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typical facial appearances downs

round face, flat nasal bridge, upslanted palpebral fissures, epicanthic folds, brushfield spots in iris, small mouth and protruding tongue, small ears, flat occiput and 3rd fontanelle

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other anomalied Downs

short neck, duodenal atresia, hirschsprung disease, delayed motor milestones, LD, small stature, incr susceptibility to infection, hearing, visual, incr leukaemia and tumours, incr atlanto axial instability, incr risk hypothyroid and coeliac, epilepsy, alzheimers

7

what can the extra chromosome 21 be due to

meiotic non disjunction, translocation, mosaicism

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what is a miotic non disjunction

most- error at meiosis. related to maternal age. can occur in spermatogenesis. pair of chromosome 21s fail to separate so one gamete has 2 lots of chromosome 21

9

if had one child with trisomy 21 due to non disjunction what is the risk of recurrence

1 in 200 if

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what translocation occurs in trisomy 21

robertsonian translocation.

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risk of recurrence downs if translocation

10-15% if mother is the carrier, 2.5% if father. if neither carries- risk of recurrence

12

what % people carrying turners miscarry

>95% end in early miscarriage

13

features turners

lymphoedema of hands and feet in neonate, spoon shaped nails, short stature, neck webbing, wide carrying angle, widely spaced nipples, congenital heart defects, delayed puberty, ovarian dysgenesis, hypothyroid, renal anomallies, pigmented moles, recurrent otitis media

14

treat turners

GH, oestrogen replacement

15

what is mosaicism

non disjunction occurs during mitosis after zygote formation. some cells are normal and some arent

16

does the risk of turners increase with increasing maternal age

no

17

what is turners

female partly or completely missing an X chromosome

18

what is PKU

phenylketonia. deficiency of the enzyme phenylalanine hydroxylase so get hyperphenylalanaemia

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features PKU

6-12m. infantile spasms, developmental delay, demyelination, decr IQ, fair heir, eczema, fits, musty urine. detected by Guthrie screening

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inheritance PKU

autosomal recessive

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effects of maternal PKU on the baby

facial dysmorphism, microcephaly, growth retardation, decr IQ

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treatment PKU

dietary restriction- on dietary phenyalanine.

23

inheritance neurofibromatosis

autosomal dominant. up to 50% new mutations

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features neurofibromatosis

6+ cafe au lait spots, axillary freckling, firm nodular neurofibrommata palpable on peripheral nerves, Lisch nodules, bony lesions

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inheritance achondroplasia

autosomal dominant. 80% new mutations

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features achondroplasia

short stature from marked shortening of limbs, frontal bossing and large head, gross motor skills develop later. bow legs, incr lumbar lordosis

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complications achondroplasia

hydrocephalus, tibial bowing, joint hypermobility, foramen magnum compression, otitis media

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what happens in noonan

point mutation. autosomal dominant. males and females affected

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features noonan

wide spaced eyes, web neck, short stature, pulmonary stenosis, hypertrophic cardiomyopathy, VSD/ASD, bruising, down slanting eyes, IQ decr

30

what is neurofibromatosis type 1

von recklinghausen, with cafe au lait etc

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what is neurofibromatosis type 2

bilateral acoustic neuroma and other CNS tumours

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inheritance tuberous sclerosis

autosomal dominant.

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features tuberous sclerosis

adenoma sebaceum on face, infantile spasms, LD, ashen leaf patches which fluoresce in UV light

34

genetics of digeorge

22q11.2

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features DiGeorge

absent thymus, anaemia, decr GH, cleft palate, heart defects, cognitive defects

36

what happens in Prader willi

loss of paternal - chromosome 15.

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features prader willi

blue eyes, blond hair, hypersomnolence. passive, autistic, introverted, unstable moods

38

genetics edwards syndrome

trisomy 18

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features edwards syndrome

rockerbottom feet, rigidity with limb flexion, odd low set ears, receding chin, proptosis, cleft lip/palate, microcephaly and micrognathia

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genetics pataus syndrome

trisomy 13

41

genetics klinefelters

one or more extra X chromosome. 47 XXY.

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features klinefelters

tall stature and long legs, small testes, gynaecomastia, LD. treat: testosterone

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features pataus

growth retardastion, micropthalmia, cleft lip and palate, cutis aplasia, polydactyly

44

how is karyotyping done

FISH- fluorescent in situ hybridisation. if the piece of DNA is there (what looking for) then the probe will stick to it and flash

45

what is microarray or CGH array

reference genomic DNA- green. test sample genomic DNA red. if same will go yellow, if patient has only one copy will be more green (losses) if patient has extra part of chromosome will be more red (gains)

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advantages microarray

higher pick up rate, faster, cheaper, reduces need for severl FISH tests which need to know what suspicions have to do it

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problems of microarray

variants of unknown significance. unexpected findings