The diagram below shows a segment of DNA with a total length of 4,900 base pairs.The arrows indicate reaction?

Question

sites for restriction enzymes

DNA Segment Lengths

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400 X 500 Y 1,200 X 1300 Y 1500

Enzyme (the letters)

(A) Explain how the principles of gel electrophoresis allow for the separation of DNA fragments.
(B) Describe the results you would expect from electrophoretic separation of fragments from the following treatments of the DNA segment above. Assume that the digestion occurred under appropriate conditions and went to completion.
I. DNA digested with only enzyme X
II. DNA digested with only enzyme Y
III.DNA digested with enzyme X and enzyme Y combined
IV. Undigested DNA

(C) Explain both of the following:
(1). The mechanism of action of restriction enzymes
(2). The different results you would expect if a mutation occurred at the recognition site for enzyme Y.
Please help

its for myself. i just want to understand it, i want to check my answers.

Answer 1

(A) the gel acts as a molecular sieve --> large molecules pass through the pores in the gel slower that smaller ones since all DNA have same charge/mass ratio and would move at the same rate without many molecular sieve.

(B)
I) 400, 800, 300 base pairs --> 3 bands
II) 500, 800, 200 base pairs --> 3 bands
III) 400, 100, 700, 100, 200 base pairs --> 5 bands
IV) one intense band of 1500 base pairs

(C)
(1) restriction enzymes (referring to restriction endonuclease II) recognize specfic palindromic sequences and cleave the DNA within the recognition sequence.

(2) enzyme Y would not recognize the site and their would be not cleavage of DNA at that site

Answer 2

Trying to get us to d your homework eh? Think of it this way, If you put a whole bunch of marbles of all different sizes in a big jar and then shake it. The big ones will fall to the bottom and the marbles wil sort themselves by size. That is the principle fo gel electrophoresis (much simplified). So you expect pieces of the DNA to separate by size.
Think of each restriction enzyme as a pair of scissors, cutting at the prescribed length. So if you only digested with X you would have two pieces (bands on the gel) one that is 400 base pairs long and one that is the rest of the molecule (4500bp). Restriction enzymes "cut" at specific places not necessarily at specific lengths so you wont end up with a DNA strand cut into 12 pieces of 400 bp each.
I have given you images, ways of thinking of the DNA and enzymes but you need to read your text to specifically describe the enzyme action and determine the answers. If you get hung up, email me, there is not enough room to help you more here.

Answer 3

Maybe we're looking for the wrong thing. And as far as why that Universal Presence (am going to stop referring to it as "God" and "Him"....doesn't really fit with my concept, and have only ever used those as terms of convenience anyhow...well maybe might let a "God" slip in every once in a while, again for convenience) is so hard to find now, that would be our fault. We've turned our backs on it, *not* the other way around. The human population lives primarily in the physical now. We've lost our connection to spirit. We don't connect to the forces around us the way we used to. We don't have to. And we're encouraged not to. In fact, it's frowned upon to do so to a certain extent. And that which we tout as "spiritual" is really nothing more than theatre and ritual. Going through the motions without true meaning. We've been miseducated IMO as to the true nature and intent of this presence, and so we are looking for the wrong thing, in the wrong places. Of course we're not going to find our way back that way.