WEEK 2 CHROMOSOME III: STRUCTURAL CHROMOSOME ABNORMALITIES

Question 1

define structural chromosome abnormality

Answer 1

a chromosome imbalance due to structural changes within the chromosomes

Question 2

common structural chromosomes

Answer 2

1. deletions
2. duplications
3. translocation
4. inversions
5. insertions
6. ring chromosomes
7. isochromosomes

Question 3

one chromosome can have

Answer 3

multiple structural abnormalities

Question 4

usually, the total number of chromosome is normal but

Answer 4

there is a change in their structure

1. missing
2. extra
3. switched-in a different place

Question 5

1. deletions

Answer 5

part of the chromosome is missing/deleted

1. it can be interstitial or terminal deletion

Question 6

some genetic material is missing in deletion

Answer 6

1. can cause syndromic features

2. depends on genes involved in the deletion

Question 7

deletion can be

Answer 7

sporadic or dorminant

if it is 50% dominant there can be a recurrence risk

Question 8

a test used for deletions

Answer 8

1. FISH
2. Array
3. MLPA
4. or Karyotype

Question 9

the genetic condition associated with deletions

Answer 9

1. Angelman syndrome= 15q11 deletion
2. Prader Willi syndrome= 15q11 deletion
3. 22q deletion syndrome= 22q11 deletion

Question 10

duplications

Answer 10

part of the chromosome is duplicated, it can be interstitial or terminal duplication
it can be direct9tandem) or inverted

Question 11

duplications result in extra genetic material

Answer 11

1. severity depends on the genes involved

2. it is less severe than deletions

Question 12

duplications can be sporadic

Answer 12

or inherited, if it is inherited there is a 50% recurrence risk

Question 13

the test used for duplications

Answer 13

1. FISH
2. Array
3. MLPA
4. OR karyotype

Question 14

genetic abnormality of duplication

Answer 14

1. 22q duplication syndrome= 22q11 duplication

Question 15

TRANSLOCATION: reciprocal

Answer 15

1. exchange of material between chromosomes

Question 16

TRANSLOCATION: reciprocal= balanced

Answer 16

1. no loss or gain of genetic material

2. the individual is phenotypically normal

Question 17

TRANSLOCATION: reciprocal= unbalanced

Answer 17

1. there will be gain or loss of genetic material- severity depends on the size
2. can be inherited from a balanced parent- recurrence is complicated.

Question 18

TRANSLOCATION: reciprocal= test

Answer 18

1. array if unbalanced

2. karyotype if balanced

Question 19

TRANSLOCATION: Robertsonian

Answer 19

exchange of material between two acrocentric chromosomes to form one large metacentric chromosome

Question 20

TRANSLOCATION: Robertsonian= example

Answer 20

45,XX,rob(13,13)(q10,q10)

Question 21

TRANSLOCATION: Robertsonian= test

Answer 21

karyotype

Question 22

inversion

Answer 22

1. portion of chromosome broke off, inverted,3. and reattached
2. can be pericentric= involves centromere

3, can be paracentric= does not involve centromere

4. if isolated the individual is often phenotypically normal which means they can be a normal variant

Question 23

inversion test

Answer 23

karyotype

Question 24

insertion

Answer 24

1. portion of a chromosome broke off and is inserted elsewhere
2. it can be interchromosomal or intrachromosomal
3. direct insertion or inverted insertion

Question 25

insertion test

Answer 25

karyotype

Question 26

ring chromosome

Answer 26

1. portion of chromosome broke off and formed a ring
2. can happen with or without loss of genetic material
3. very rare
4. often severe
5. usually sporadic

Question 27

ring chromosome test

Answer 27

karyotype

Question 28

isochromosome

Answer 28

formed by a mirror copy of a chromosome segment

result in a gain and loss of genetic material

Question 29

isochromosome test

Answer 29

1. FISH
2. Array
3. MLPA
4. or karyotype

Question 30

isochromosome disorder

Answer 30

1. Pallister Killian syndrome= isochromosome 12