Question 1 1 Point • What two properties of DNA result in...

Question 1 1 Point • What two properties of DNA result in the requirement that some DNA is replicated using Okazaki fragments? This is a multiple answer question (not a multiple choice). More than one answer should be chosen. (A) The DNA contains a phosphate-suger backbone. (B) The DNA double helix is antiparallel. (C) The DNA contains bases that always pair A to T and G to C. (D) Both strands of DNA are replicated simultaneously by a multiprotein enzyme complex.

Transcript

00:01 In order to answer this question, let's talk about base pairing.

00:03 According to base pairing in dna, you're going to have that adenine is going to pair with timing and cytosine with one.

00:10 This question number one says for the dna sequence that we have here three prime, this is three, okay? you have g, c, c, c, t, and 5, right? this is one in dna strand, okay? the sequence found is in the complementary dna strand must be, and well, we have to use base pairing in order to construct the complementary base dna strand.

00:36 So here we're also going to remember that the dna and the polystyne molecule is antiparral.

00:41 It means here you're going to have the 5 end and here you're going to have the 3 end.

00:44 And here you're going to have c, g, g, a, t, a, and that's going to be your dna strand, your complementary dna strand.

00:52 So you really have to look for the hoveett answer here and you're going to see that the answer for this question is going to be option a that says 5n c.

01:02 G g, a t .a.

01:04 3n.

01:05 Then we have the next question that says leading and lagging dna strand exists at a replication form because, well, remember that if this is your dna, and this is the like where dna replication is happening, this is going to be the 3 -end, and this is the 5 -end, and this is the 5 -end, and this is a 3 -end.

01:22 Remember that, well, let's suppose here that the helic cases are opening the stand in this direction.

01:27 And also remember that your dna polymerase is the enzyme that is going to polymerize a new strand, and it does its work in a 5 -3 direction.

01:38 So in this case, you have 3 -end and 5 -n.

01:41 So as we have talked here, remember that both strands are going to be ant -parallel.

01:44 So the newly synthesized strand had to go from 5 to 3.

01:47 So your dna polymerized is going to polymerase in this direction, from 5 to 3.

01:54 So it is polymerizing in the same direction as the helicase.

01:57 Are opening that two strands.

01:59 So as the early cases keep opening the strands, this dna polymerase is going to continue working.

02:04 So, practically nothing is going to happen.

02:06 And what about here? or well, this strand is called the leading strand.

02:10 And what about this strand that is called the landing strand? well, in this strand, it goes from 5 to 3.

02:16 So your dna polymer is going to synthesize in this direction from 5 to 3.

02:21 So as you can see here, well, let's make it like smaller, okay? like this.

02:27 5 to 3.

02:29 So as it is synthesizing in an encrifice, opposite direction to the helicases because remember that this part of the dna is going to be like that, it's going to be like this.

02:39 So as you can see, the it is going or the dna polymerity synthesizing in like an opposite direction to the helicase job.

02:49 So once dna polymerase ends here, it's going to come back here and it is going to polymerize again in this direction.

02:56 And the same here and so long as the helicases keep opening this strand.

02:59 Okay.

03:00 So this is called the lagging strand.

03:02 And as you can see here, it is a discontinuous process in contrast to this.

03:06 And these fragments are called ocasaki fragments...

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