9. (a) (i) How are the two strands of a DNA molecule joined together?
(ii) What is ‘junk’ DNA?
(b) Answer the following questions by referring to the procedures that you used to isolate DNA from a plant tissue - Leaving Cert Biology - Question 9 - 2011
Question 9
9.
(a) (i) How are the two strands of a DNA molecule joined together?
(ii) What is ‘junk’ DNA?
(b) Answer the following questions by referring to the procedur... show full transcript
Worked Solution & Example Answer:9. (a) (i) How are the two strands of a DNA molecule joined together?
(ii) What is ‘junk’ DNA?
(b) Answer the following questions by referring to the procedures that you used to isolate DNA from a plant tissue - Leaving Cert Biology - Question 9 - 2011
Step 1
How are the two strands of a DNA molecule joined together?
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Answer
The two strands of a DNA molecule are joined together by hydrogen bonds.
Step 2
What is ‘junk’ DNA?
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Answer
'Junk' DNA refers to non-coding regions of DNA that do not code for proteins.
Step 3
What was the first procedure that you followed?
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Answer
The first procedure followed was to chop the plant tissue into smaller pieces.
Step 4
What was the reason for that procedure?
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Answer
Chopping the tissue helps to disrupt its structure and increase the surface area for further processing.
Step 5
Washing-up liquid is then used in the isolation. Give a reason for its use.
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Washing-up liquid is used to disrupt cell membranes, allowing the DNA to be released.
Step 6
Salt (sodium chloride) is also used in the isolation. Give a reason for its use.
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Salt is used to clump the DNA together and to protect it from other positive ions during the isolation process.
Step 7
What is a protease?
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A protease is an enzyme that digests proteins.
Step 8
Why is a protease necessary when isolating DNA?
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A protease is necessary when isolating DNA because DNA is often bound to proteins that need to be broken down.
Step 9
Describe how freezer-cold ethanol is used.
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Freezer-cold ethanol is added slowly or down the side of the test tube to help the DNA precipitate out of solution.
Step 10
For what purpose is it used?
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Freezer-cold ethanol is used to bring the DNA out of solution so that it can be collected.
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