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Can't do this question! Gel electrophoresis, A2

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Can't do question 3!

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Reply 1
clue: the shortest fragment travels the furthest in the gel and longest the slowest (least amount of distance)
the fragments are at the negative electrode and move towards the positive electrode- they are negative due to the phosphoryll group and are attracted to the positive electrode :smile:
Reply 2
Original post by MedMed12
clue: the shortest fragment travels the furthest in the gel and longest the slowest (least amount of distance)
the fragments are at the negative electrode and move towards the positive electrode- they are negative due to the phosphoryll group and are attracted to the positive electrode :smile:


I understand that but I still dont understand the answers to 3.

My initial answer to 3a was four, but the answer is two??
My initial answer to 3b was Thymine??

:confused::confused::confused:
Reply 3
Original post by Seatbelt
I understand that but I still dont understand the answers to 3.

My initial answer to 3a was four, but the answer is two??
My initial answer to 3b was Thymine??

:confused::confused::confused:



What are the original answers to 3?


In 3a, you must count the no of adenine bases. That is represented by bands on the diagram. The bands are clearly two in number.

In 3b, the sequence of DNA is worked from bottom to top, antiparallel to the direction of electrophoresis. You can now work out the position of the nucleotide.
My initial answer to 3a was four, but the answer is two??

- unless they mean how many A bases in the gel? Otherwise 4 Adenine would be the right answer.

My initial answer to 3b was Thymine??

3b should be cytosine - it is the first complementary base that is added, so gives the smallest fragment.

:confused::confused::confused:
As flowerscat says, a) is badly worded. There are four adenine bases in the strand being sequenced, and two in its complementary strand.

b) Cytosine is the answer. Shorter strands move further through the gel, and the strand nearest the bottom is in the cytosine lane.

c)

Spoiler

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