Brainscape's Knowledge GenomeTM

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


See full index

Peadiatrics > Genetic Disordes > Flashcards

Genetic Disordes Flashcards

1
Q

3 triosmies

A

Downs - 21 - 1:700
Edwards - 18 - 1:8000
Pataus - 13 - 1:15000

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

Facial features of downs

A

Round, epicanthic folds, flat nasal bridge, small ears, protruding tongue, brushfield spots on iris (pigmented)

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

Non facial dysmorphic features downs

A

Wide sandal gap, incurring little fingers, single palmar crease

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

Structural defects downs

A

Cardiac in 50%

Duodenal atresia

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

Neurological feature downs

A

Hypotonia, developmental delay , decreased IQ (~50)

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

Late medical complications of downs

A

Increased risk of leukaemia (CML); Alzheimer’s; hypothyroidism; atlantoaxial instability

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

What is atlantoaxial instability

A

Excessive movement of atlas and axis on neck -> can cause nerve root compression

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

The 3 cytogenetic causes of downs (with%)?

A

Non dysjunction (94%)
Translocation (4%)
Mosaicism 1%

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

What happens in non-dysjunction

A

The two chromosomes 21 fail to separate so one gamete has 2 copies -> fertilisation of this gamete give a trisomy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Are non dysjunctions usually maternal or paternal? What increases risk? What’s the recurrence risk?

A

90% maternal.
Increasing age (over 35)
1 in 200 (if

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

What happens in translocation

A

The extra chromosome 21 is joined onto another chromosome (usually 14) giving rise to an unbalanced robertsonian translocation
The affected child has 46 chromosomes but still 3 copies of 21 material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Recurrence risk in translocation

A

10-15% if mother
2-3% if from father
If the parent carried 21:21 translocation 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens in mosaicism ? How severe ?

A

Non dysjunction occurs during mitosis after fertilisation
Some cells have tri-21 and some don’t
Often has a milder phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Genotype in tuner syndrome ? How common? How often does this result in miscarriage ?

A

45X
1:2500 live born female
95% miss carry

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

What’s seen on antenatal USS of turners

A

Oedema of the neck, hands, feet or a cystic hygroma

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

What are the cytogenetics of turners (physiology)?

A

50% have 1 X chromosome

50% have deletion in the short arm of 1 X chromosome (isochromosome - 2 long arms) or other structural defects

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

Dysmorphic features of turners

A 
Lymphoedema of hands and feet at birth 
Neck webbing
Short stature 
Shield chest (wide spaced nipples) 
Wide carrying angle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Structural / functional defects in turners

A

Gonadal dysgenesis (primary amenorrhoea) - streak ovaries
CHD - esp coarctation of aorta
Renal anomalies

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

Management of turners ? Explain rational of each?

A

Growth hormone to improve final height

Oestrogen therapy at 11 years -> allows development of secondary sexual characteristics

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

Klinefelter’s syndrome genetics? How common? Features? What mat be required?

A

47xxy
1:1000 live born males
Infertility, hypogonadism, gynaecomastia in adolescence ,tall stature
pubertal development usually normal but may need supplemental testosterone

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

Egs of some deletion syndromes ? Where are the deletions

A

Cri du chat syndrome - tip of chromosome 5
Dr’ George’s syndrome - in chromosome 22
William’s syndrome - long arm of chromosome 7

22
Q

Features of cri du chat

A

High pitched cry in infancy “cri du chat’

23
Q

How is analysis of dr George syndrome done? Features?

A

Cytogenetics analysis using FISH
Developmental delay, learning difficulty, ritualistic behaviour & obsessions, conductive hearing loss, T cell deficiency , hypocalcaemia

24
Q

Why do dr George syndrome get conductive hearing loss? T cell deficiency?

A

Recurrent otitis media

Absent thymus

25
Q

Features of Williams syndrome

A

Short stature, mild learning difficulty, CHD, transient neonatal Hypercalcaemia (sometimes), faces

26
Q

What facial features in Williamsons ? What CHD?

A

Low nasal bridge, ‘elf-line’

Supra valvular aortic stenosis

27
Q

AD single parent affected chance of passing on ?

A

50%

28
Q

Eg of AD inheritance with variable expression

A

Tuberous sclerosis

29
Q

What is non penetrance ? Eg?

A

Lack of signs and symtoms in individual who has the abnormal gene
Otosclerosis

30
Q

What can cause no FHx of AD disorder

A

New mutation in gametes
Mosaicism
Non-paternity

31
Q

Egs of AD diseases

A

Neurofibromatosis
Huntington’s
Achrondroplasia
Familial hypercholesterolaemia

32
Q

Risk of AR disease if both parents are carriers? What can increase risk?

A

25%

Consanguinity

33
Q

Egs of AR diseases

A

Cystic fibrosis, thalassaemia, sickle cell, congenital adrenal hyperplasia, inborn errors of metabolism

34
Q

What happens in X linked disorders ? Who is affected?

A

Carrier female on 1 X chromosome (other is normal)

only males affected but females can be mildly

35
Q

X linked disorder father ? Effect on children

A

All daughters are carriers

No sons are carriers

36
Q

Egs of X linked disorders

A

Haemophilia , duchenne muscular dystrophy, fragile X syndrome, red/green colourblindness

37
Q

How common is fragile X? What is it due to?

A

1:1000 males, 1:2000 females

Trinucleotide repeat of expansion of triplet repeat CGG in the FRAXA gene FMR1

38
Q

Features of fragile X

A 
Moderate-severe learning disability
Macrocephaly
Macro-orchidism (post pubertal) 
(Mitral valve prolapse, joint laxity, scoliosis, autism, hyperactivity) 
Faces
39
Q

Facial features of fragile X

A

*Broad forehead
Large everted ears
Prominent mandible *

40
Q

What are the two most common genetic causes of learning difficulties

A

Downs

Fragile X

41
Q

How are mitochondrial disorders inherited ? Egs?

A

Maternally
*MELAS (to remember) *
Mitochondrial encephalopathy, lactic acidosis, stroke like episodes

42
Q

What is genomic imprinting

A

Only one copy of the gene (from mother or father is expressed)
Maternal allele imprinted - only express paternal allele
Paternal allele imprinted - only express maternal

43
Q

2 ways for a child to fail to inherit active gene?

A
  • De novo deletion* - parental chromosomes normal with a new mutation
  • uniparental disomy* - when a child inherits 2 copies of a chromosome from 1 parent and none from the other
44
Q

Eg of imprinting? Where is defect ?

A

Paternal deletion - Prader-Willi syndrome
Maternal deletion - Angleman’s syndrome

Can get due to disomy too!!! Not just deletion

Both have defective gene at *15qII-B *

45
Q

Features of prayer-Willi

A

Learning difficulty, obesity, hypotonia

46
Q

Features of Angleman’s

A

“Happy puppet” - severe learning difficulty, ataxia, epilepsy, characteristic face

47
Q

Basic elements of genetic counciling

A

Establishing a diagnosis
Estimation of risk
Communication

48
Q

How do you establish a diagnosis?

A

Physical exam

Special investigations - DNA, cytogenetics, biochemical analysis

49
Q

What risk do you have to calculate after a diagnosis

A

Chance of future offspring being affected

50
Q

How do you communicate genetic disorders

A

Conveyed in an unbiased and non-directive way with all the possible options being discussed

Peadiatrics (14 decks)

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