Congenital genetic abnormalites

Question 1

What are the 4 Single congenital abnormalities?

Answer 1

Malformation
Disruption
Deformation
Dysplasia

Question 2

What are the 3 multiple congenital abnormalities?

Answer 2

Sequence
Synndrome
Association

Question 3

What is malformation?

Answer 3

Primary structural defect.
Usually involves single organ with multi-factoral inheritance
(e.g. genetic & environmental)

Question 4

What is Disruption?

Answer 4

Secondary structural abnormality.
Caused by ischaemia, infection or trauma
Genetically predisposed

Question 5

What is Deformation?

Answer 5

Mechanical forces causing abnormal form, shape or position.

Occurs late in pregnancy, good prognosis as underlying structure is normal.

Question 6

What is Dysplasia?

Answer 6

Abnormal organisation of genes into tissues.

Caused by single gene defect

Question 7

What is a Sequence abnormality?

Answer 7

Pattern of multiple associated abnormalities from single factor

Question 8

What are Syndrome abnormalities?

Answer 8

Consistent pattern of abnormalities that are pathogenetically related

Question 9

What are association abnormalities?

Answer 9

Non-random occurence of abnormalities with unknown cause and not explained by syndrome

Question 10

Give two examples of Malformations:

Answer 10

Atrial Septal Defect

Cleft Lip

Question 11

Give two examples of deformations:

Answer 11

Club foot

Hip dislocation

Question 12

Give an example of a Sequence abnormality:

Answer 12

Potter Sequence

Oligohydroamnios - reduced amniotic fluid

Question 13

Give an example of a congenital syndrome:

Answer 13

Downs Syndrome - trisomy 21

Question 14

What are the three categories of Chromosome abnormalities?

Answer 14

Structural
Numerical
Mosaicism

Question 15

What are structural chromosome abnormalities?

Answer 15

Translocations
Deletions
Insertions
Inversions
Duplications
Rings

Question 16

What is a numerical chromosomal abnormality?

Answer 16

Aneuploidy

Question 17

What is aneuploidy?

Answer 17

Loss or gain of chromosomes

Question 18

What are the two arms of a chromosome called?

Answer 18

q arm - long arm
p arm (petite) - short arm

Question 19

What are the three centromere locations called?

Answer 19

Metacentric - central centromere
Submetacentric - centromere more towards one side
Acrocentric - No short arms, satellites instead.

Question 20

What is the shorthand for giving a location on a chromosome?

Answer 20

Chromosome number
p or q arm
Band number

e.g. 6q21

Question 21

Which aneuploidys can be tolerated?

Answer 21

Trisomy
Tetrasomy

Monosomy - nearly always fatal

Question 22

When can a Robertsonian translocation occur?

Answer 22

On acrocentric chromosomes

13,14,15,21,22

Question 23

What is a balanced carrier?

Answer 23

Carry a translocation, but have Disomy, so are unaffected

Question 24

Which trisomys can be viable?

Answer 24

+13, +18, +21

Question 25

What is trisomy 13?

Answer 25

Patau syndrome

Mental retardation and heart defects

Question 26

What is Trisomy 18?

Answer 26

Edwards syndrome

Mental retardation and heart defects

Question 27

What is Trisomy 21?

Answer 27

Down's syndrome
Robertsonian t(21:21)

Question 28

What is dosage compensation?

Answer 28

Ensures equivalent gene expression in both sexes via random inactivation of a single X chromosome in a mosaic pattern; Barr bodies are formed by Xist inactivation - no matter how many x chromosomes you have only one stays active