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 procedures... 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 encode for proteins.
Step 3
Having obtained a plant tissue e.g. onion, What was the first procedure that you followed?
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Answer
The first procedure that I followed was to chop the onion.
Step 4
What was the reason for that procedure?
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The reason for chopping the onion was to disrupt its structure and to increase the surface area.
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 membranes.
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 and to protect it from other positive ions.
Step 7
What is a protease?
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A protease is an enzyme that digests protein.
Step 8
Why is a protease necessary when isolating DNA?
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A protease is necessary when isolating DNA because DNA is combined with proteins.
Step 9
Describe how freezer-cold ethanol is used.
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Freezer-cold ethanol is added down the side of the test tube or added slowly.
Step 10
For what purpose is freezer-cold ethanol used?
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The purpose of using freezer-cold ethanol is to bring the DNA out of solution.
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