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Human genetics > G6- Chromosomal abnormalities and syndromes > Flashcards

G6- Chromosomal abnormalities and syndromes Flashcards

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Biology 101 flashcards
1
Q

How common are chromosomal diseases?

A

Mostly rare. No clear pattern of inheritance. Usually low risk to relatives

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2
Q

why is staining used on genes?

A

used to obtain complex banding patterns that allow precise identification of each chromosome and recognition of small additions or deletions

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3
Q

what is the short arm of a chromosome?

A

p

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4
Q

what is the long arm of the chromosome?

A

q

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5
Q

what chromosomes are abnormalities found on?

A
  • trisomies 13,18,21

- extra sex chromosomes

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6
Q

what are the types of chromosomal abnormalities?

A

Structural: translocations, deletions and duplications

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7
Q

How does age affect the number of incidences?

A

incidences increase with maternal age

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8
Q

what syndrome is trisomy 21?

A

Downs sydrome (1 in 800)

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9
Q

what are phenotypes of downs syndrome?

A
  • Upslanting palpebral fissures
  • Middle third hypoplasia
  • Flat nasal bridge
  • Open mouth posture
  • Protruding fissured tongue
  • Low set ears
  • Short stature
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10
Q

what syndrome is trisomy 13?

A

Patau syndrome (1 in 5000)

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11
Q

what are phenotypes of patau syndrome?

A

convergence of left and right side of the brain

  • small eyes or Cyclops
  • cleft lip/palate
  • simian crease (hand)
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12
Q

what syndrome is trisomy 18?

A

Edwards syndrome (1 in 3000)

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13
Q

what are phenotypes of Edwards syndrome?

A 
Narrowpelvis
• Small jaw
• Clenched hands with overlapping digits
• Congenital heart defects
• Cleft palate
- Many die before the age of 1
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14
Q

Why is there only trisomies in 13,18,21?

A

trisomies in other chromosomes result in spontaneous abortions

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15
Q

what is a syndrome of a single X chromosome?

A

Turner syndrome (1 in 5000)

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16
Q

what is the phenotype of turners syndrome?

A
  • Normal external vaginal organs
  • Uterus and fallopian tubes present
  • Neither ovaries (nor testes)
  • Growth retardation / Webbed neck
  • Bone and heart problems
  • infertility
17
Q

what is SRY?

A

-Some species (including humans) have a gene SRYon the Y chromosome that determines maleness (produces TDF)
• Human sex is determined by containing SRY or not
• When SRY is activated, cells create testosterone to turn the genderless sex organs into male
• SRY-reliant species can have conditions such as XXY and still viable (but may display features of both sexes)
• SRY and sex determination e.g. was once used in Olympic games

18
Q

Name a syndrome that affects sex of humans.

A

Kleinfelters (XXY) (<2 per 1000)

19
Q

name a syndrome as a result of chromosomal deletion.

A

Velocardiofacial syndrome

20
Q

what are problems with Velocardiofacial syndrome?

A

Developmental delays Speech problems
Cardiac problems
Cleft palate
Mental Health

21
Q

what are general clinical features that commonly occur in patients with chromosomal abnormalities?

A
  • Developmental delay (physical / mental)
  • Short stature
  • IQ / cognition / speech
  • Congenital heart problems
  • Cleft palate
22
Q

name congenital abnormalities.

A
  • Malformations
  • Disruptions
  • Deformations
  • Syndromes
23
Q

what is malformation?

A

primary structural defect occurring during development of an organ or tissue e.g. CP, CL(P)

24
Q

what is aetiology?

A

single gene, multifactorial, environmental, teratogen or unknown

25
Q

what is a syndrome?

A

The presence of multiple anomalies simultaneously in the same individual giving a pattern of malformation
- Implies a common cause for all the anomalies

26
Q

Describe disruption : hemifacial microsomia.

A

Destruction of part of a foetus that had initially developed normally
(Foetus is genetically normal and risk of recurrence is low)

27
Q

What are examples of Disruption: Hemifacial microsomia?

A

-atypical facial clefts, digit or limb
amputations caused by amniotic bands.
-Hemifacial microsomia caused by
-haemorrhage/haematoma at the stapedial artery

28
Q

what is deformation due to?

A

Due to abnormal intra-uterine moulding in either a healthy or malformed foetus

29
Q

what are the 2 categories of mental retardation in down syndrome?

A

(a) Profound - institutionalised (b) Mild - community dwelling

30
Q

what can down’s syndrome result in?

A
  • Cardiac abnormalities (50%)
  • Resistance to infection
  • Leukaemia (more prevalent)
31
Q

what are dental problems of downs syndrome?

A

-Dental caries - resistant
• Periodontal disease - susceptible
• Malocclusion - common
• Dental anomalies - hypodontia, microdontia, delayed eruption

32
Q

How does downs syndrome affect dental management?

A 
-Communication problems
• Anxiety/Restlessness
/Stubborness
• Access/macroglossia/Salivation
• Cross infection - ? Hep B
• Susceptibility to infection
• Antibiotic cover
• Poor G.A. risk

Human genetics (5 decks)

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