Chromosomal Abnormalities and Syndromes

Question 1

What are the types of genetic disease?

Answer 1

1. Chromosomal: No pattern of inheritance
2. Single gene: Clear pattern of inheritance. High risk to relatives.
3. Multifactorial: No pattern of inheritance
4. Somatic mutation (Congenital Abnormalities)

Question 2

What are Down Syndrome more resistant to but also more susceptible to?

Answer 2

Down Dyndrome patients are resistant to caries but more susceptible to periodontal disease

Question 3

What is the structure of a G-banded chromosome?

Answer 3

Question 4

What are the 2 types of Chromosomal Abnormalities?

Answer 4

1. Numerical - trisomies 13, 18, 21. Extra sex chromosomes.
2. Structural: translocations, deletions and duplications.

Question 5

What are the chrosomal abnormality’s that cause Cleft lip/palate?

Answer 5

• Trisomy 13 - Patau’s
• Trisomy 18 – Edwards

Question 6

What is SRY?

Answer 6

• 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

Question 7

What are some problems of Velocardiofacial syndrome: 22q11 deletion?

Answer 7

• Speech problems
• Cleft palate

Question 8

What are the Congenital Abnormalities?

Answer 8

• Malformations
• Disruptions
• Deformations
• Syndromes

Question 9

What is Malformation?

Answer 9

A malformation is a primary structural defect occurring during development of an organ or tissue.

Note: Multiple malformations occurring simultaneously = syndrome.

Question 10

What is Disruption?

Answer 10

Destruction of part of a foetus that had initially developed normally.

Question 11

What is Deformation?

Answer 11

In a foetus with no abnormalities, breech presentation, multiple pregnancy or uterine abnormalities may cause deformation, e.g. Congenital dislocation of the hip.

Question 12

What is a Syndrome?

Answer 12

The presence of multiple anomalies simultaneously in the same individual giving a pattern of malformation.

Question 13

What are Down’s syndrome phenotypes?

Answer 13

• Upslanting palpebral fissures
• Middle third hypoplasia
• Flat nasal bridge
• Open mouth posture
• Protruding fissured tongue
• Low set ears
• Short stature
• Mental retardation - variable 2 categories:

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

• Cardiac abnormalities (50%)
• Resistance to infection
• Leukaemia

Question 14

What are dental problems with Down Syndrome?

Answer 14

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