Genetic Test

Question 1

Genetic test

Answer 1

Xp22.3
chromosome x
arm p
region 2
brand 2
subband 2

Question 2

Types of chromosomal aberrations

Answer 2

1. Numerical

2. Structural

Question 3

Types of structural variation

Answer 3

Insertions
Deletions
Duplications
Inversion	
Translocation

Question 4

Unbalanced translocation

Answer 4

Translocation where the exchange of chromosome material is unequal resulting in extra or missing genes

Question 5

Balanced translocation

Answer 5

Translocations can be balanced (in an even exchange of material with no genetic information extra or missing, and ideally full functionality)

Question 6

Which types of structural variants are balanced vs unbalanced?

Answer 6

Insertions, Deletions, Duplications are unbalanced
Inversion are balanced
Translocation can be both

Question 7

derivative chromosome

Answer 7

chromosome that has an intact centromere

Question 8

acrocentric chromosome

Answer 8

having the centromere situated so that one chromosomal arm is much shorter than the other — compare metacentric, telocentric entry 1

Question 9

Karyotype

Answer 9

Changes in the number of chromosomes
Deviations from normal banding patterns Large (>5-10Mb) insertions or deletions, translocations and inversions
from one cell

Question 10

Fluorescent in situ hybridization (FISH)

Answer 10

employs a fluorescently labeled probe to detect and localize the presence or absence of a specific DNA sequence

Collections of smaller probes, each of which binds to a different sequence along the length of a given chromosome. Using multiple probes labeled with a mixture of different fluorescent dyes, such that each chromosome has its own unique color. The resulting full-color map of the chromosome

Question 11

What does karyotype not detect?

Answer 11

Small structural abnormalities
Small sequence variants (INDELS and SNPs)
Copy neutral LOH (like uniparental disomy)

Question 12

Spectral Karyotyping (SKY)

Answer 12

• Detected with FISH
• Non-targeted approach
• Great to detect inter-chromosomal aberrations - complex chromosome rearrangements, translocations, large INDELS)

Question 13

What does FISH– Utility detect?

Answer 13

Changes in the number of chromosomes
Large (>500 Kb-2 Mb) insertions or deletions, and translocations
Useful to look at mosaicism

Question 14

What does FISH– Utility not detect?

Answer 14

Small structural abnormalities (< 500Kb)
(Inversion)
Small sequence variants (INDELS and SNPs)
Copy neutral LOH (like uniparental disomy)

Question 15

Microarray (oligo array)

Answer 15

From multiple cells

a ton of fish experiments at one

Question 16

resolution

Answer 16

on the number of probes used and their distribution through the genome – you only see regions represented in the array

Question 17

What does a “normal” array result mean?

Answer 17

No losses or gains of currently known clinical significance
Does not rule out mosaicism
Does not rule out areas of the genome not covered by the array design
Does not rule out variants that do not result in losses or gains of material (copy neutral LOH and balanced rearrangements, as well as small sequence variants like INDELS and SNPs)

Question 18

What will Oligo array- alpha GCH-utility detect?

Answer 18

Changes in the number of chromosomes
Relatively small (as small as 1Kb) insertions or deletions
(Unbalanced translocations

Question 19

What will Oligo array- alpha GCH-utility will not detect?

Answer 19

Balanced structural abnormalities
Inversion
Small sequence variants (INDELS and SNPs)
Copy neutral LOH (like uniparental disomy)

Question 20

What acan Single Nucleotide Polymorphisms and Oligo Array detect?

Answer 20

Changes in the number of chromosomes
Relatively small (as small as 1Kb) insertions or deletions
Copy neutral LOH (like uniparental disomy)
(Unbalanced translocations)

Question 21

What Single Nucleotide Polymorphisms and Oligo Array will not detect?

Answer 21

Balanced structural abnormalities
Inversion
Very small sequence variants (except the SNPs on the array!)

Question 22

What type of assays are good at detecting Chromosomal mosaicism

Answer 22

FISH (it’s fast and easy)
Karyotype (it’s possible but labor intensive)
Oligo + SNP arrays (header to detect unless you have a lot of cells with the missing chromosome because you combine cell samples)

Question 23

Chromosomal mosaicism

Answer 23

use FISH on a large number of cells (>200) in multiple tissues

Question 24

Microdeletions

Answer 24

FISH if possible

CMA (Chromosomal microarray) may not detect mosaicism less than 20-25

Question 25

Small sequence changes

Answer 25

use sequencing (Sanger or NGS on multiple tissues)