1. What type of replicating DNA is positive heteropyknosis?: Late replicating
DNA
2. What are some characteristics of positive heteropyknosis?: dark G and Q bands, light R bands, C bands, late replicating, positive heteropyknosis, hete- rochromatin, inactive, A-T rich
3. What type of replicating DNA is negative heteropyknosis?: early replicating
DNA
ASCP CG Certification Practice Exam Questions And Answers
4. What are some characteristics of negative heteropyknosis?: light G and
Q bands, dark R bands, early replicating, negative heteropyknosis, euchromatin, active, C-G rich
5. What is the chromosome banding code?: first letter=type of banding, second letter=general technique used, third/last letter=stain used
6. GTG: G banding by trypsin using Giemsa stain
7. QFQ: Q banding by fluorescence using quinicrine dihydrochloride or quinicrine mustard
8. RFA: R banding by fluorescence using acridine orange
9. RHG: R banding by heat using Giemsa stain
10. CBG: C banding by barium hydroxide using Giemsa stain
11. Who discovered G banding and in what year?: Seabright in 1971
12. Who discovered Q banding and in what year?: Caspersson in 1970
13. Who discovered R banding and in what year?: Dutrillaux and Lejeune in
1971
14. Who discovered C banding and in what year?: Arrighi and Hsu in 1971
15. Which enzyme is used for the G banding technique: trypsin
16. What factors determine treatment time for G banded slides?: age of the slide, concentration of trypsin, pH of trypsin
17. When do slides become resistant to trypsin?: the longer they sit at room temperature, the longer they are heat treated, and more they are treated with denaturing chemicals like hydrogen peroxide
18. What is the optimal concentration of a trypsin solution?: 0.01% trypsin diluted in Hanks w/o Ca or Mg ions
19. What is Giemsa stain?: a heterochromatic, purple, stain that is a mixture of eosin and methylene blue stains ASCP American Society for Clinical Pathology
20. What is the optimal Giemsa solution?: a 4% Giemsa stain w/phosphate buffer
21. The intensity of the Giemsa stain is a function of what?: time and concen- tration
22. What stain is used for Q banding: Quinicrine dihydrochloride or quinicrine mustard
23. What is the name of the buffer used for Q bandiing? What is its pH?: Mel- vaine’s buffer; pH of 5.5-6.0
24. Why is a thin layer of buffer necessary between the slide and coverslip when Q banding?: to swell the chromosomes, increase contrast, allow flourescent light to travel to the objectives
25. What regions does Quinicrine preferentially bind to?: A-T regions
26. Which regions is Q banding useful?: Y chromosome, centromeres of chro- mosomes 3 and 4, satellites of D and G groups
27. What is C banding?: A technique which stains the constitutive heterochro- matin located around the centromeres of chromosomes
28. Which chromosomes generally have the largest C band region?: 1,9,16,Y
29. What are the two types of heterochromatin?: constitutive and facultative
30. What is constitutive heterochromatin?: the inactive heterochromatin locat- ed around the centromeres of chromosomes and the distal long arm of the Y chromosome
31. What is facultative heterochromatin? Give an example: euchromatic DNA that has been rendered inactive by cellular processes. An example would be the inactive “X” in females
32. How are C band polymorphisms useful?: to distinguish fetal cells from maternal cells, donor cells from host cells, to identify markers, and to identify paracentric/pericentric inversions
33. What does silver staining do?: Stains the NORs of metaphase chromo- somes and the nucleolus of interphase cells
34. What does NOR stand for?: nuclear organizing regions
35. What are NOR’s (nuclear organizing regions): the satellite regions on chro- mosomes 13,14,15,21,and 22
36. What does the acronym FISH stand for?: Fluorescent in situ Hybridization
37. What is FISH or fluorescent in situ hybridization?: A cytogenetic technique that uses fluorescent probes that bind to or hybridize to specific DNA sequences.
38. What are the three types of probes used in FISH?: unique sequence probes, satellite probes, painting probes
39. What are repetitive sequence probes?: probes that hybridize to specific areas of repetitive DNA. (typically alpha, beta, and classical satellite sequences)… Examples are centromere probes, Y specific probes
40. What are painting probes, and what are some examples?: probes that hy- bridize to large areas of specific DNA. Examples are: whole chromosome probes, partial chromosome probe, total genomic probes
41. What are unique sequence probes?: probes that hybridize to a locus specific site in the human genome
42. What are the three main step in the FISH technique/procedure?: denatu- ration, hybridization, post hybridization wash
43. Explain what is involved in the denaturation process?: double stranded
DNA becomes single stranded DNA that hybridizes with target DNA
44. How is DNA treated during the process of denaturation?: in 2xSSC and
70% formamide at 70 degrees celsius
45. What is formamide?: an organic solvent that lowers the melting point of DNA
46. What is involved in the hybridization step of the FISH procedure?: The
DNA probe is hybridized to the target dna on specimen slides at 37 degrees celsius
47. What is involved in the post hybridization wash: A 2xSSC or another buffered salt wash is used to remove free or unwanted probe
48. What is stringency?: The extent of removal of unwanted probe?
49. What are the usual fluorochromes used in FISH?: FITC (green), rhodamine
(red), Texas Red (deep red)
50. Why is a counterstain used in FISH?: To view either the interphase nucleus or metaphase chromosomes
51. What counterstain is preferred for rhodamine or texas red?: DAPI (blue)
52. What counterstain is preferred for FITC green?: propidium iodide
53. What is LISH: Light in situ hybridization uses nonfluorescent probes to detect target dna
54. nonisotopic LISH technique: uses enzymatic reactions to visualize sub- strates
55. isotopic LISH technique: uses radioactive probes to expose film
56. What is the appropriate width and refractive index of FISH coverslips?: –
width=0.17mm and refractive index=1.515
57. What should be the refractive index of the mounting media?: 1.515
58. What are three ways slides can be destained?: Carnoy’s fixative, methanol,
70% ethanol
59. What substances will remove oil completely from the slide?: Xylene or
Hemo-D
60. How is hydration or rehydration of a slide accomplished?: by exposing the slide to various dilutions of ethanol moving from low to high
61. How is dehydration of a slide accomplished?: by exposing the slide to various mixtures of ethanol from high to low
62. How long are slides required to be stored in New York before disposal?: 6 years
63. What should be done to prevent destruction of stored slides due to humidity and airborne dust?: they should be stored in an airtight container in a humidity and temperature controlled environment
64. Name some ways slides can be aged before G-banding.: storage at room temperature from 3 days to six weeks, heated overnight at 60 degrees celsius, heated for 2 hrs. at 75 degrees celsius, heated for 20 minutes at 901 degrees celsius, treated with 15% hydrogen peroxide
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