Chromosomal Abnormalities Flashcards Preview

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Flashcards in Chromosomal Abnormalities Deck (14)
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1
Q

Name 3 examples of trisomies.

A
  • Down syndrome (most common)
  • Edwards syndrome (2nd most common)
  • Patau syndrome (3rd most common)
2
Q

What causes Down syndrome?

A
  • Usually free standing trisomy 21.

- Can also result from unbalanced Robertsonian translocation.

3
Q

What are the symptoms of Down syndrome?

A
  1. Intellectual disability
  2. Hypotonia (lack muscle tone)
  3. Characteristic facial features
  4. Heart defects
4
Q

What are the health consequences of Down syndrome?

A
  • Increased prevalence of leukaemia

- Increased incidence of early Alzheimers’

5
Q

What are the causes of Edwards’ syndrome?

A
  • Usually free-standing trisomy 18

- Involves maternal meiosis II error

6
Q

What are the symptoms of Edwards syndrome?

A
  1. Antenatal growth deficiency
  2. Specific craniofacial features:
    - small lower jaw
    - low-set ears
  3. Major systems malformations
    - rocker bottom feet
    - overlapping fingers
  4. Cognitive developmental delay
7
Q

What is the modal lifespan in Edwards syndrome?

A

5-15 days

8
Q

In which gender is Edwards syndrome more prevalent?

A

Females

9
Q

What are the causes of Patau syndrome?

A
  • Usually free standing trisomy 13

- Can also result from unbalanced Robertsonian translocation

10
Q

What are the symptoms of Patau syndrome?

A

Multiple congenital abnormalities, e.g. Polydactyly and holoprosencephaly (brain doesn’t divide in 2 halves, can present with cleft lip)

11
Q

What is the lifespan in Patau syndrome?

A

Majority die in neonatal period

12
Q

Name an example of a monosomy.

A

Turner syndrome (45,X)

13
Q

What are the symptoms of Turner syndrome?

A
  1. Short stature (monosomic for SHOX gene)
  2. Mild learning difficulties
  3. Infertility
  4. Neck webbing
14
Q

Why is the loss of an X chromosome problematic?

A
  • X and Y chromosomes have short regions in common (PAR1 and PAR2 pseudo-autosomal regions) at the tips of the short and long arms, allowing for pairing during cell division.
  • Turner patients will be monosomic for genes in the PARs, e.g. SHOX gene associated with short stature.