DNA from strawberry

Question 1

What are the 5 general steps to extracting DNA?

Answer 1

-break plant cell walls open by frictional force
-break cells and disrupt nuclear membranes
-use enzymes to remove proteins
-add salt to make DNA less soluble
–once insoluble in water, precipitate the DNA using organic solvent

Question 2

What is step 1 of DNA extraction from a strawberry?

Answer 2

-crush strawberry with 20cm3 DNA extraction buffer in ziploc bag, with pestle and mortar

Question 3

How does step 1 help?

Answer 3

-extraction buffer contains detergent (disrupts phospholipid bilayer) and salt (neutralises charge of phosphate groups in backbone so DNA is less soluble in water)
-crushing breaks cell walls
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Question 4

What is step 2 of DNA extraction from a strawberry?

Answer 4

Strain this into beaker using tea strainer and muslin

Question 5

How does step 2 help?

Answer 5

removes cell debris and membrane fragments so that filtrate contains only DNA and histones

Question 6

What is step 3 of DNA extraction from a strawberry?

Answer 6

-add 1cm3 of protease enzyme to filtrate

Question 7

How does step 3 help?

Answer 7

-protease enzymes digest histones, leaving just DNA (eg pepsin or papain)

Question 8

What is step 4 of DNA extraction from a strawberry?

Answer 8

pour filtrate into boiling tube

Question 9

What is step 5 of DNA extraction from a strawberry?

Answer 9

-add 1cm3 ice cold ethanol to filtrate
-tib boiling tube to 45 degrees and slowly roll ethanol down inside wall of tube so it forms layer on top of filtrate

Question 10

How does step 5 help?

Answer 10

-nucleic acids are insoluble in ice cold ethanol
-salt in buffer makes DNA less soluble in water based filtrate so it forms a precipitate

Question 11

What is step 6 (final) of DNA extraction from a strawberry?

Answer 11

-Let it stand for 5 minutes
-Scoop out white precipitate with inoculating loop