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Flashcards in hodgson Deck (122)
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1

what is the g banding protocol

1. cells cultured to generate mitotic cells
2. arrest cell cycle in metaphase
3. swell nuclei with hypotonic solution
4. kill cells using fixative
5. drop fixed sample onto glass slide
6. trypsin digest
7. leishmans stain
8. image analysis

2

why do bands appear dark and light

dark bands are AT rich - open chromatin
pale bands are GC rich - closed chromatin

3

what does fixative do

block chromosome condensation, kill everything in sample eg removes infectious disease

4

what can the centromere be referred to as

p10 or q10

5

which type of fish is not used clinically in the UK

indirect label FISH

6

what does trisomy 18 lead to

edwards syndrom

7

wha does trisomy 13 lead to

pateu syndrome

8

what does a small deletion of 5p lead to

cri du chat

9

what does banding resolution depend on

1. cell cycle stage
2. tissue sample
3. experimental (slide aging, staining time, chromosome spread)

10

what are the steps to direct labelling FISH

1. take microscope slide with DNA
2. make target DNA single stranded by heating sample to 75-78 degrees
3. Anneal probe at 37-40 degrees
4. series of washes to remove unbound probes
5. DAPI used as a counter stain

11

what are the 3 main types of FISH probe

1. chromsome enumeration probes for common aneuploidies
2. microdeletion probes
3. whole chromosome pait

12

when would you use whole chromosome paint

when youre unsure of origin of a chromsome

13

At high concentrations what inhibits ribinucleotide reductase which converts CDP to dCDP meaning the concs of dCTP become rate limiting and the lymphocytes remain in S phase

dTTP

14

how can we cause S phase synchronisation

high levels of dTTP

15

how is the thymidine block released

washing (centrifugation)
- addition of dCTP

16

which is the preferred way of releasing the thymidine block

addition of CTP to bypass the need for ribonucleotide reductase (what excess dTTP is limiting)

17

why is addition of CTP the preferred method of overcoming the thymidine block

health and safety risk to centrifugation - can fracture a tube and a sample may be contaminated with infectious disease

18

what is another way of synchronising cells in S phase

addition of Fdu

19

how does addition of Fdu cause cells to be synchronised in S phase

excess Fdu blocks the synthesis of dTMP which is a precursor of dTTP so reduces its availability for DNA synthesis

20

how can the Fdu block be released

addition of excess dTTP but addition of too much can block the cycle again by inhibiting ribonucleotide reductase

21

what is colcemid

microtubule inhibitor that arrests cells in metaphase

22

how does colcemid inhibit microtubules

binds to soluble tubulin, colcemid-tubulin complex may still polarise but with significantly reduced efficiency
microtubule stability is reduced, preventing spindle formation

23

what are the 4 main sections of quality

accuracy, precision, specificity and sensitivity

24

what do we mean by accuracy

a test is accurate when the true abnormality is identified

25

what do we mean by precision

a test is precise when repeated analyses yield the same result over and over again

26

when is a test specific

when false positive rate is low

27

when is a test sensitive

when false negative rate is low

28

what QA is used in fertility services

QA4

29

what is much more susceptible to structural arrangements

spermatogenesis - oogenesis is much more robust

30

rDNA encoded on p arm of acrocentric chromosomes 13,14,15,21,22. Repetitive DNA can be lost or gained with no abnormal clinical phenotype T/F

T