cytogenteics

Question 1

Reasons for cytogenetic screening (Prenatal analysis)

Answer 1

Abnormal NIPS
Advanced maternal age
Abnormal US
Family history of chromosome abnormality
Maternal anxiety

Question 2

Reasons for cytogenetic screening postnatal

Answer 2

Family history
Multiple miscarriages
Birth defects
Development delay
Confirm prenatal diagnosis

Question 3

Steps for g banding

Answer 3

Culture
Colcemid- arrest in metaphase
Hypotonic solution
Stain
Analyze

Question 4

G banding advantages

Answer 4

Rapid and robust

Detection of numerical abnormalities, structural rearrangements, large deletions/duplications

Question 5

Disadvantages G banding

Answer 5

Lots of training
Minimal detection size is 5-10 Mb
Low level/tissue specific mosaicism missed
Epigenetic changes not seen
Cancer- no dividing cells- no chromosomes to analyze

Question 6

Fish advantages

Answer 6

Doesn’t require dividing cells
Quick screening of many cells
Rapid results
Excellent for confirming G banding analysis results
Detect tissue-specific mosaicism
Expanded list/improved detection chromosome alterations

Question 7

Disadvantages of FISH

Answer 7

Requires physician to suspect diagnosis
Size of detected imbalance is depended on probe size
Each probe is costly
Doesn’t detect epigenetics

Question 8

DNA microarray analyzes

Answer 8

Copy number variations

Question 9

Microarray advantages

Answer 9

Can detect up to 5 Kb
Small amount of DNA needed
Comprehensive evaluation of genetic imbalances
Mapping of deletion/duplication to specific chromosome
Prior knowledge of nature of genetic aberration not needed

Question 10

Microarray disadvantages

Answer 10

Wont detect balanced chromosome rearrangements
Wont detect imbalances in regions not included
Challenge in interpretation of DNA CNVs
Sensitivity for low level mosaicism reduced by normal cell contamination or tumor heterogeneity