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Paediatrics > Genetics > Flashcards

Genetics Flashcards

1
Q

How common are genetic diseases?

A

4-5% of all live births
30% of admissions to paediatric wards - congenital abnormalities
10% adults have disease with genetic component
5% common cancers such as breast and colon cancer due to underlying genetic predisposition

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2
Q

What is the role of a clinical geneticist?

A

Involved in making diagnoses
Explain diagnosis to family
Discuss prognosis
Discuss options available - genetic testing, screening, prenatal diagnosis
Refer to appropriate specialist for management
Help people understand and adapt to medical, psychological, and familial implications of how genetic contributes to disease
Guide individuals/families in discussions about test result interpretation, prevention, medial management, and options for prenatal diagnosis
Not involved in diagnosis

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3
Q

What referrals do clinical geneticists get?

A 
Preconceptual - genetic testing
Antenatal - scans/tests
Paediatrics - not meeting milestones ect
Carrier testing
Adult onset conditions
Post mortem
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4
Q

What are the categories of genetic disorders?

A

Single gene disorders - mendelian inheritance
Chromosomal disorder - affects thousands of genes so multiple organ systems affected
Multifactorial - several genes acting with environmental influences, usually only affects one organ system
Spectrum of conditions

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5
Q

Name 3 types of genetic disease

A

Down’s syndrome
CF
Huntington’s disease
Haemophilia

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6
Q

Name 3 types of multifactorial disease

A

Spina bifida
Cleft lip/palate
Diabetes
Schizophrenia

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7
Q

Name 3 types of environmental disease

A

Poor diet
Infection
Accidents
Drugs

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8
Q

What are the different types of single gene disorders?

A

Autosomal dominant
Autosomal recessive
X-linked

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9
Q

What can cause chromosomal abnormalities?

A

Changes in number/structure

Entire chromosomes/individual chromosomes/alterations within individual chromosomes

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10
Q

What is polyploidy?

A

Increase in number

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11
Q

What is it called where you lose a chromosome?

A

Monsomy

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12
Q

What is it called where you gain a chromosome?

A

Trisomy

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13
Q

What is euploidy?

A

Normal number of chromosomes

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14
Q

What is aneuploidy?

A

Abnormal number of chromosomes

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15
Q

What is a common cause of aneuploidy?

A

Non-disjunction
Failure of chromosomes to separate at anaphase
Can occur in meiosis 1/2

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16
Q

Name 2 causes of chromosomal conditions

A

Unbalanced translocation

Non-disjunction

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17
Q

What should you do if a baby has chromosome translocation?

A

Test the parents

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18
Q

How common in aneuploidy?

A

35-70% of early embryonic deaths and spontaneous abortions caused by aneuploidy
1 in 170 live births

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19
Q

What are the possible clinical effects of cytogenetic abnormalities?

A

Congenital abnormalities
Delayed development - usually severe
Dysmorphic features
Small stature, microcephaly, failure to thrive
In adults - infertility, stillbirths, miscarriages

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20
Q

How might autosomal dominant inheritance present in a family?

A

Each child has 50% chance of inheriting mutation
Equally transmitted by men and women
Often affected individuals in multiple generations
Vertical transmission
Mutation transmitted from male to male
Sex can be limited
Only one copy of gene pair altered
May have variable penetrance and often variable expression
Possibility of new mutations
Gonadal mosaicism may occur

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21
Q

Name 3 causes of autosomal dominant inherited conditions

A 
Adult PKD
Familial hypercholesterolaemia
Marfan's
Huntington's disease
Familial breast and ovarian cancer
22
Q

What is gonadal mosaicism?

A

Condition in which the precursor cells to ova and spermatozoa are a mixture of 2 or more genetically different cell lines

23
Q

What is autosomal recessive inheritance?

A

2 germline mutations to develop disease

24
Q

How might autosomal recessive conditions present in families?

A

Equally transmitted by men and women
Unless consanguinity usually only one generation affected
Both parents heterozygous carriers
1 in 4 recurrence risk for siblings
2 in 3 carrier risk for unaffected siblings
Usually low risk for children of affected person or half-siblings - depends on population carrier frequency
Increased risk in consanguineous families

25
Q

Name 3 conditions that are autosomal recessively inherited

A 
CF
PKU
Haemochromatosis
SMA
Non-syndromic sensori-neural deafness
26
Q

How might x-linked inheritance present in families?

A

Genes carried on x chromosome
More males than females affected
Females carriers - 50% sons affected, 50% daughters carriers
All daughters of affected male are carriers
None of offspring of affected male have disorder
Possibility of new mutations
Gonadal mosaicism may occur
Influenced by x inactivation

27
Q

Name 2 causes of x-linked diseases

A

Duchenne and Becker muscular dystrophy
Fragile X
Retinitis pigmentosa
Ocular albinism

28
Q

Name 3 types of non-mendelian inheritance

A

Multifactorial
Imprinting
Mitochondrial inheritance
Mosaicism

29
Q

What causes neural tube defects?

A

Multifactorial

30
Q

What can decrease the chance of neural tube defects?

A

Taking folic acid in pregnancy can decrease risk by up to 70%

31
Q

What is the risk of neural tube defects if have an individual in family already affected?

A

1 sibling 2%
2 siblings 10%
Parent 4%

32
Q

What can increase risk of neural tube defects?

A

Maternal diabetes

33
Q

What causes mitochondrial disorders?

A

Exclusively maternally inherited deriving from those present in cytoplasm of ovum
Tends to affect those tissues that use the most energy

34
Q

What is in the mitochondria?

A

Contain own circular 16.5Kb chromosome

35
Q

What is heteroplasmy?

A

Mixed population of normal and abnormal mitochondria

36
Q

Name 3 types of mitochondrial disease

A

MELAS - mitochondrial encephalopathy lactic acidosis stroke like episodes
MERRF - myoclonic epilepsy, ragged red fibres
DIDMOAD - mitochondrially inherited DM and deafness
Leber’s hereditary optic atrophy

37
Q

What is genomic imprinting?

A

For most genes both copies are expressed

Some genes are maternally or paternally expressed - imprinting

38
Q

Name 2 conditions that involve genomic imprinting

A

Prader-Willi
Angelman’s
Caused by cytogenetic deletions of the same region of chromosome 15q or by uniparental disomy of chromosome 15 (both copes of 15 come from same parent)

39
Q

How does Prader-Willi syndrome present?

A

Neonatal hypotonia and poor feeding
Moderate mental retardation
Hyperphagia and obesity
Small genitalia

40
Q

What caused Prader-Willi syndrome?

A

Caused by deletion in paternally inherited chromosome 15 or maternal uniparental disomy

41
Q

How does Angelman’s syndrome present?

A 
Happy puppet unprovoked laughing/clapping
Microcephaly
Seizures
Ataxia
Broad based gait
42
Q

What causes Angelman’s syndrome?

A

Deletion in maternally inherited chromosome 15 or parental uniparental disomy

43
Q

How often are cancers referred to clinical geneticits?

A

Around 50% of all referrals

44
Q

What genes can cause breast and ovarian cancer?

A

BRCA1 and 2

45
Q

What genes can cause bowel cancer?

A

Lynch
(A)FAP
MYH
Other polyposis genes

46
Q

What is fragile x syndrome and how is it inherited?

A

Most common form of learning disability

X-linked

47
Q

How common is fragile x syndrome?

A

Females don’t always have clinical features - approx 30% have some learning disability
1 in 2000 males affected (approx 80% undiagnosed)
1 in 600 carriers (some of premutation)

48
Q

How does fragile x syndrome present?

A

IQ of young boys seems to steadily decline so as children may only be mild/moderately affected, adults males usually have an IQ under 50
Long narrow face
Prominent ears
Hyper-extensible joints
Emotional and behavioural problems common in both sexes if affected

49
Q

How does the genetics of unaffected individuals differ from those with fragile x syndrome?

A

Unaffected - 10-50 copies of triplet repeat CGG

Fragile X - 50-200 premutation unstable during cell division likely to expand to full mutation of more than 200 repeats

50
Q

When is the heel prick test done in children?

A

Day 5 of life

51
Q

What is tested for in the heel prick test?

A 
Sickle cell disease
CF
Inherited metabolic disorders
- Phenylketonuria
- Medium-chain acyl-CoA dehydrogenase deficiency
- Maple syrup urine disease
- Isovaleric acidaemia
- Glutaric aciduria type 1
- Homocystinuria

Paediatrics (21 decks)

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