Pre-natal genetic diagnosis

Question 1

2 methods of chromosome analysis

Answer 1

Karyotyping+ FISH

Question 2

Karyotyping use what cells?

Answer 2

Proliferating cells cultured with Colchicine

Question 3

karyotyping method

Answer 3

1) Arrest cells in metaphase =condensed chromatin
2)cells in hypotonic solution = cells swell
3) fix in methanol or acetic acid
4) cells burst and Chromosomes stick on slide= metaphase spread
5) Brief digestion with Trypsin
6) Staining ( Giemsa/ Leishman’s) = Bands

Question 4

Why arrest cells in metaphase?

Answer 4

Chromatin condensed + chromosomes visible

Question 5

2 types or bands

Answer 5

Major measured from centromere
Minor bands within major

Question 6

Karyotyping + FISH example diagnosis

Answer 6

Di George Syndrome (deletion) loss of red, retention of green

Question 7

What FISH use

Answer 7

fluorescent labelled DNA probes bind + highlight specific chromosomes

Question 8

FISH: cell in what cycle

Answer 8

metaphase spread or Inter phase

Question 9

FISH highlights?

Answer 9

whole chromosome or localized region

Question 10

Counterstain

Answer 10

DAPl= blue to visualise total chromatin

Question 11

Metaphase v interphase FISH cells

Answer 11

M= cultured cells
I= fresh or archival material

Question 12

FISH method

Answer 12

1) chromosomes denatured = SSDNA
2) DNA probe labelled with fluorescent molecule e.g nucleotide
3) probes denatured
4) Probes hybridized
5) wash off excess
6) counterstain with DAPI

Question 13

M- FISH/ Spectral Karyotyping difference

Answer 13

chromosomes have diff colours

Question 14

Fluorochrome labels are

Answer 14

chemically bound to nucleotides

Question 15

stokes Shift

Answer 15

shift in peak excitation to emission

Question 16

Fluorochrome label examples

Answer 16

Texas Red
FITC (green)

Question 17

cut off filter

Answer 17

only see emitted light

Question 18

chorionic Villus Biopsy (CVB)

Answer 18

Removal of foetal tissue from chorionic Villus 11-15 weeks

Question 19

Why use CVB

Answer 19

Detect unknown or expected abnormalities

Question 20

Amniocentesis

Answer 20

foetal Keratinocytes shed in to Amnionic fluid test fluid

Question 21

Pre-natal testing must

Answer 21

Be only foetal cells

Question 22

How Pre implantation diagnosis works

Answer 22

Removal of single cells from fertilized egg + screen for mutations then implant by IVF

Question 23

Pre -natal + pre implantation differences

Answer 23

PGD= rests Blastomeres
PND = Tests on foetus in utero

Question 24

Pre implantation method

Answer 24

1) ovarian simulation
2) fertilization
3)1 cell from Blastomere removed
4) Genetic analysis
3) unaffected embryo transferred

Question 25

material used in Pre implantation (x3)

Answer 25

Polar body, Blastomere Biopsy, Blastocyst Biopsy ( later)

Question 26

Risks Of Pre- Implantation

Answer 26

Embryo damage, IVF risks (no pregnancy), Misdiagnosis, expensive+ labour intensive