Unit 1: Genomic DNA from plant - Practice Quiz

1 What does the abbreviation CTAB stand for?

2 The CTAB method is primarily used to extract which type of biomolecule?

3 What is the chemical nature of CTAB detergent?

4 Why is the CTAB method especially preferred for plant tissues?

5 Which technique is commonly used to break down the rigid plant cell wall before adding CTAB buffer?

6 What is the typical role of -mercaptoethanol in the CTAB extraction buffer?

7 What is the main function of EDTA in the CTAB extraction buffer?

8 The organic solvent mixture chloroform:isoamyl alcohol is used mainly to:

9 In the chloroform:isoamyl alcohol mixture, what is the usual ratio used?

10 After centrifugation of the aqueous phase, which reagent is commonly added to precipitate the DNA?

11 During DNA precipitation, why is the sample often kept at low temperature?

12 Which alcohol concentration is generally used to wash the DNA pellet to remove salts?

13 What is the purpose of incubating the ground tissue with CTAB buffer at around ?

14 Which enzyme is often added to the extracted DNA to remove RNA contamination?

15 In the CTAB protocol, what is commonly used to finally dissolve and store the purified DNA?

16 Which technique is commonly used to check the quality and integrity of extracted genomic DNA?

17 The purity of extracted DNA is commonly assessed using the absorbance ratio at:

18 A high concentration of NaCl in the CTAB buffer mainly helps to:

19 At what wavelength does DNA show maximum absorbance, used for quantification?

20 During phase separation, in which layer is the genomic DNA found?

21 In the CTAB method of plant DNA extraction, what is the primary function of the detergent CTAB (cetyltrimethylammonium bromide)?

22 Why is a high salt concentration (typically NaCl) maintained in the CTAB extraction buffer?

23 What is the role of -mercaptoethanol when added to the CTAB extraction buffer?

24 During CTAB extraction, a chloroform:isoamyl alcohol (24:1) mixture is used. What is the purpose of the isoamyl alcohol component?

25 Why is plant tissue typically ground in liquid nitrogen before adding CTAB buffer?

26 After the chloroform extraction step, in which phase is the genomic DNA found?

27 Isopropanol (or chilled ethanol) is added to the recovered aqueous phase in the CTAB protocol. What does this step accomplish?

28 Why is a ethanol wash performed on the DNA pellet after precipitation?

29 A student's extracted DNA has an ratio of . What does this most likely indicate?

30 Why is the CTAB method particularly preferred over standard SDS-based methods for many plant tissues?

31 Polyvinylpyrrolidone (PVP) is often added to the CTAB buffer for plants rich in phenolics. What is its function?

32 The CTAB extraction buffer is commonly incubated at –. What is the main reason for this incubation?

33 EDTA is a common component of CTAB extraction buffers. Why is it included?

34 Tris-HCl (usually at pH ) is a component of the CTAB buffer. What role does it play?

35 To obtain RNA-free genomic DNA using the CTAB method, what treatment is typically applied?

36 A student sees a bright band of intact high molecular weight DNA but also a strong smear at the bottom of an agarose gel. What does the smear most likely indicate?

37 During DNA precipitation, the sample is often incubated at . What is the benefit of this step?

38 Why should vigorous vortexing be avoided during the CTAB extraction of genomic DNA?

39 The purified DNA pellet is finally dissolved in TE buffer rather than distilled water. Why is TE buffer preferred for storage?

40 If a plant DNA sample shows an ratio well below (e.g., ), what contamination is most likely present?

41 In the CTAB extraction buffer, CTAB (cetyltrimethylammonium bromide) is a cationic detergent. At the working temperature of , what is its primary mechanism for enabling DNA purification from plant tissue?

42 A student's CTAB buffer contains M NaCl. If the salt concentration accidentally drops to M during extraction, what is the most likely consequence?

43 -mercaptoethanol (typically ) is added to CTAB buffer. In plant tissues rich in phenolics, what is its specific protective role?

44 During chloroform:isoamyl alcohol () extraction, what is the specific function of the isoamyl alcohol component?

45 After isopropanol precipitation, a student observes a ratio of . What does this most likely indicate?

46 A DNA preparation shows of but of . What is the most probable interpretation?

47 Why is isopropanol often preferred over ethanol for precipitating genomic DNA in the CTAB protocol?

48 The final DNA pellet is washed with ethanol rather than ethanol. What is the rationale?

49 RNase A treatment is included in the CTAB protocol. At which stage is it most effective and why?

50 A researcher grinds fresh leaf tissue in liquid nitrogen before adding CTAB buffer. What is the primary purpose of this step?

51 For plant tissues extremely rich in polysaccharides (e.g., some fruits), increasing NaCl to M in CTAB buffer helps because:

52 EDTA is a standard component of CTAB buffer (typically mM). Its essential role in preserving DNA integrity is to:

53 Tris-HCl at pH is used in CTAB buffer. Why is a pH of approximately specifically chosen over acidic pH?

54 On an agarose gel, a CTAB-extracted genomic DNA sample shows a bright high-molecular-weight band plus a low-molecular-weight smear near the dye front. What is the most likely explanation?

55 If DNA extracted by CTAB fails to amplify in PCR despite good yield, and the ratio is very low, the most probable PCR inhibitor is:

56 A protocol recommends warming the CTAB buffer to before adding ground tissue and incubating min. Which combination of purposes does this heating serve?

57 During phase separation after chloroform extraction, in which layer is the genomic DNA found and why?

58 A student obtains a very low DNA yield and notices excessive foaming and an unclear interphase during chloroform extraction. Which procedural error most likely caused this?

59 PVP (polyvinylpyrrolidone) is sometimes added to CTAB buffer for plants like tea or grape. Its specific function is to:

60 Given for a diluted DNA sample (dsDNA factor per unit), what is the DNA concentration of the original undiluted stock?