Page 17 - Biology - XII

Q2. Mention the need for using frozen material for isolation of DNA.
Ans. Keeping the material frozen prevents the disintegration of the DNA before extraction.

Q3. What do you understand by isolation of DNA?
Ans. Isolation of DNA means separation of DNA from the cell/cellular contents.

Q4. Mention the temperature at which the plant mixture must be incubated.
Ans. 60°C
Q5. What is CTAB-extract solution? Why is it used?
Ans. It is an extract solution and is buff er in nature. It disables the nucleases that breaks down the DNA.
It also combines with proteins, polysaccharides, and chemically alters them.

Q6. Mention the reasons for complexity in isolation of DNA from plant tissue.
Ans. (i) Presence of cell walls in plant tissue which needs to be broken.
(ii) Presence of special cell inclusions in the cell sap/cytoplasm which needs to be seperated.

Q7. What is the use of centrifuge?
Ans. Centrifuge is a device used to separate materials based on their size and density at diff erent speeds
by centrifugal force.
Q8. What do you know about gel electrophoresis?
Ans. It is a technique used for seperation of DNA fragments based on their electronegativity which is
relative to their molecular size.
Q9. Where is DNA located in a plant cell?
Ans. (i) Nucleus (ii) Chloroplast

Q10. Which gel is used in the electrophoresis?
Ans. Agarose gel

Q11. What do you understand by spooling?
Ans. Spooling is the method of removal or separating/isolating DNA from the solution using a glass rod
or wooden spool. (Analogy: Removal of egg albumin from broken egg using a spoon.)
Q12. Mention any two uses of isolated DNA.
Ans. (i) Finger printing (ii) Ligation

COMPETENCY BASED QUESTIONS

Multiple Choice Questions

Q1. Plant density is expected to be more in which season?
(a) Winter (b) Rainy (c) Summer (d) Spring

Q2. According to Raunkiaer (1934) there are
(a) two classes of frequency % (b) three classes of frequency %
(c) four classes of frequency % (d) fi ve classes of frequency %

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