Genetic Lab Diagnostics

Question 1

Chromosome Analysis Prep Process (4)

Answer 1

Culture cells on mitosis stimulating medium, arrest in metaphase w/ colcemid, then treat w/ KCl and centrifuge out chroms

Question 2

5 Common Sources of Chromosomes

Answer 2

Lymphocytes (blood)
Fibroblasts (skin)
Amniocytes
Bone marrow
Placental tissue

Question 3

2 G Bands

Answer 3

Dark bands (G+) are AT rich and gene poor
Light bands (G-) are GC rich and gene rich

Question 4

Band Numbering

Answer 4

From centromere to telomere along each p and q arm

Question 5

3 Things to Give Chromosome Location of a Gene

Answer 5

Regions
Bands
Sub-bands

Question 6

4 Indications to Request a G-Band Chrom Analysis

Answer 6

Recurring miscarriages/stillbirths
Infertility (before invasive fertilization techniques)
Immediately when Down/Turner/Klinefelter syndrome or autosomal trisomy suspected
Characterization of malignant tumors

Question 7

Basic Form of Karyotype Nomenclature

Answer 7

[Total # of Chromsomes], [sex chromosomes], variation acronym,([arm][region][band].[sub-band])

Question 8

Pericentric Inversions (3)

Answer 8

Creates a loop
Has 5-10% risk of unbalanced inversion for progeny (depending on size of inversion)
Partial duplication/deletions in the 2 imbalanced chromosomes

Question 9

FISH Benefits (2)

Answer 9

Can see smaller microdeletions than G-band

Can rapidly diagnose aneuploidys

Question 10

Microarray Benefit

Answer 10

Can detect nearly any unbalanced structural abnormality so often first genetic test done

Question 11

Oligoarray vs. SNP array

Answer 11

Oligo tests all loci for all well-known micro del/duplication syndromes
SNP even better, detects uniparental disomy and regions of homozygosity (consanguinity)

Question 12

6 Things Microarray Doesn’t Test for

Answer 12

Low-level mosaicism
*Balanced rearrangements (karyotype for that)
Small dels
Small dups
Point muts
Triplet repeat extensions

Question 13

Copy Number Variant (CNV)

Answer 13

Del or dup of whole gene too small to be detected on karyotype

Question 14

How to tell if CNV Causative of a Gene or just familial?

Answer 14

Test parents and see if they have it too/have the phenotype

Question 15

6 General Indications for Requesting a Microarray

Answer 15

Multiple malformations or unknown dysmorphism syndrome
Unexplained fetal demise(s) or stillbirth
Psychomotor developmental delays
Growth disturbances
Increased risk for fetal chromosomal disorder (like advanced maternal age or previously affected child)
Positive family history for chromsomal abnormality