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FRCPath Genomics > 10 - chromosomes > Flashcards

10 - chromosomes Flashcards

1
Q

List the clinical features of 1p36 del

A

Devdel, Hypotonia, delayed/absent speech, behavioural problems, eye defects (80% patients), distinctive facies

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2
Q

How can the 1q21 TAR syndrome micro deletion syndrome arise

A

The 1q21 region contains 4x large blocks of Low Copy Repeats (LCRs) which mediate NAHR

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3
Q

What are the features of TAR syndrome

A

TAR - thrombocytopenia Absent Radius Syndrome:
Absent Radii (bones in forearm) with presence of thumbs
Congenital / early onset thrombocytopenia
easy brushing and frequent nose bleeds

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4
Q

What micro deletion resides at 4p16

A

Wolf Hirchsorn

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5
Q

what are the clinical features of Wolf Hirchsorn Syndrome

A

1) typical facial appearance - greek warrior helmet
2) Growth delay
3) MR
4) Seizures

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6
Q

Cri-du-chat is caused by deletions where?

A

5p15.2

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7
Q

What are the clinical features of Cri-du-chat

A

1) High pitched monochromatic (cat-like) cry
2) microcephaly
3) MR
4) distinctive facial features

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8
Q

What is the likely inheritance of Cri-du-chat

A

80% de novo, 15-20% due to parental balanced structural rearrangment

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9
Q

what is the recurrence risk of 5p15.2 del

A

If arisen de novo, negligible.

If inherited, 8-18%

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10
Q

What micro deletion is associated with SOTOS

A

5q35

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11
Q

What are the causes of SOTOS syndrome

A

5q35 micro deletion encompassing the NSD1 gene most common, but SNVs in the NSD1 gene also a cause

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12
Q

What are the clinical features of SOTOS syndrome

A

Excessive Physical Growth in early years.
Leads to large body size
Macrocephaly
Characteristic facies with disproportionately large head
LD

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13
Q

7q11.23 deletion is associated with….

A

Williams Syndrome

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14
Q

what are the causes of Williams Syndrome

A

7q11.23 microdeletion

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15
Q

What is the causative gene in Williams Syndrome

A

ELN - encodes elastin

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16
Q

What are the clinical features of Williams syndrome

A

1) Cardiovascular disease
2) distinctive ‘elfin’ facies
3) connective tissue anomalies
4) mild LD
5) overly friendly, ‘cocktail party’ personality

17
Q

Name a micro deletion syndrome on 7q21

A

Split hand/foot malformation

18
Q

8p23.1 has both benign and pathogenic CNVs. What causes this

A

Due to unequal crossover between 2 olfactory receptor (OR) gene clusters flanking a 5mb region in 8p23.1

19
Q

What are the features of the 8p23.1 microdeletion syndrome?

A

1) Dev delay
2) behavioural problems
3) congenital heart disease - due to GATA4 deficiency
4) diaphragmatic hernia

20
Q

Name 4 conditions associated with Chromosome 11

A

1) Beckwith Wiedemann
2) Russell Silver
3) WAGR syndrome
4) Potock-Shaffer

21
Q

What are the characteristics of WAGR syndrome

A 
Caused by 11p13 deletion:
W - Wilm's Tumour - caused by WT1 gene
A - Aniridia - caused by PAX6 gene
G - Genitourinary anomalies
R - Retardation (mental)
22
Q

What are the characteristics of 15q13.3 microdeletion syndrome

A

1) Neuro developmental issues - due to HI of CHRNA7 gene
2) inc devdel and delayed speech
3) epilepsy
4) variable penetrance - 75% inherited

23
Q

The 16p13.3 micro deletion causes….

A

Rubinstein-Tayb syndrome

24
Q

What are the characteristics of Rubinstein-Tayb syndrome

A

1) short stature
2) moderate to severe ID
3) distinctive facies
4) eye abnormalities
5) heart & kidney defects

Note: deletions are more severe and inc:

a) FTT
b) Seizures

25
Q

What conditions are associated with Chromosome 17 microdeletions

A

1) Miller Dieker - 17p13.1
2) CMT / NHPP - 17p13.2
3) Smith Magenis - 17p11.2

26
Q

What are the characteristics of Miller Dieker syndrome. What is the causative gene

A
  • Lissencephaly
  • brain malformations
  • severe ID
  • seizures
  • microcephaly
  • LSI1 gene
27
Q

What are the characteristics of Smith Magenis syndrome. What is the causative gene

A 
> mild-mod ID
> delayed speech
> distinctive facies
> sleep disturbances
> behavioural issues inc temper tantrums and self harm
> RAI1 gene
28
Q

What are the features of Cat-eye syndrome.

A

1) Ocular coloboma
2) Preauricular skin tags
3) anal anomalies
4) cardiovascular defects

29
Q

What is the cause of Cat-eye syndrome

A

inv dup(22)pter-q11.2 (tetrasomy 22q11)

30
Q

What are the features of 22q11 deletion

A

> Variable phenotype, but can include

  • cardiac defects (tetralogy of fallout)
  • cleft palate
  • LD
  • Speech and language delay
31
Q

Define a marker chromosome

A

abnormal chromosome which cannot be distinguished by conventional cytogenetic investigations

32
Q

What are the most common chromosome origin found in marker chromosomes

A
  • 70% acrocentric
  • 70% of these are derived from chr15
  • of the 30% non-acrocentric, half are inv dups (e.g. i(12p) or i(18p)

FRCPath Genomics (12 decks)

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