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Flashcards in Genetic Lab Diagnostics Deck (15)
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1

Chromosome Analysis Prep Process (4)

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

2

5 Common Sources of Chromosomes

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

3

2 G Bands

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

4

Band Numbering

From centromere to telomere along each p and q arm

5

3 Things to Give Chromosome Location of a Gene

Regions
Bands
Sub-bands

6

4 Indications to Request a G-Band Chrom Analysis

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

7

Basic Form of Karyotype Nomenclature

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

8

Pericentric Inversions (3)

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

9

FISH Benefits (2)

Can see smaller microdeletions than G-band
Can rapidly diagnose aneuploidys

10

Microarray Benefit

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

11

Oligoarray vs. SNP array

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

12

6 Things Microarray Doesn't Test for

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

13

Copy Number Variant (CNV)

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

14

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

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

15

6 General Indications for Requesting a Microarray

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