1 all of the following are true of dna polymerase except...

All of the following are true of DNA polymerase except: Select one: a. It reads the DNA template from 3'→5' b. It is a significant cause of mutations c. It has proofreading ability d. It synthesizes DNA from 3'→5' e. It adds complementary nucleotides to the growing DNA strand 2. If there are 8 chromosomes in a somatic cell of a diploid female Drosophila melanogaster fruit fly, there would be (4,8,16,32) chromosomes and (4,8,16,32) chromatids in a cell in G1. (choose 1) 3. Certain cancer medications are S-phase specific. These types of medications would target enzymes involved in: Transcription Translation DNA replication Mitosis Select one: a. 3 only b. 1 and 2 c. 1 only d. 1, 2 and 3 e. 4 only

Transcript

00:01 Let's look at this question one by one.

00:03 The first one says all the following are true except.

00:07 So this topic is about dna replication.

00:09 Let's take a look at the dna replication itself.

00:12 The dna replication starts from the middle, which is the origin of replication.

00:16 So the dna in one itself, so the helix open and two strands of dna separate, and then they will be synthesized or replicated differently.

00:27 So as you can see, the origin is in the middle, and then there is a thing called lestration fula.

00:37 This is where dna twisted itself and unwind the helix structure that would open up the bubble in the middle for replication to happen.

00:48 You can see the replication fork actually move away from the original.

00:53 So let's take a look at how the two strands are synthesized.

00:58 Let's look at the leading strand first, which is the top one.

01:01 The top strand, a light blue one or aqua one, is a a template.

01:06 So the dna polymerase binds to the dna template right here, and it reads the sequence on the template from the three to five sections.

01:20 And the same time, it produced newly synthesized dna strand, this is a new one, in a five to three directions.

01:33 So you can see for the top strand, the leading strand, the new strand is being synthesized.

01:38 From the origin of the replication towards the same direction as the replication fork in a five to three direction manner, and also it's a continuous synthesized strand.

01:52 So this is the top strand.

01:54 The bottom one is a little different.

01:56 Again, it starts from the origin of replication.

01:59 This is the first piece right here.

02:01 We call it o 'kazaki fragment.

02:03 The reason for lagging strand or bottom strand to have discontinued.

02:08 New fragment is again because dna polymerase can only synthesize the new strand from five to three.

02:18 So it has to go backwards.

02:20 The first piece start from here.

02:26 So this is the dna polymerase.

02:29 Again, it reads the dna template from five to three directions.

02:35 At the same time, make new strength from five to three.

02:40 Redirect.

02:42 Okay.

02:43 When the first piece is finished, the second piece starts from here.

02:50 Again, dna polymerase is going to apply to the template again, and then synthesize the second piece in the same manner from five to three.

03:00 So, and then that's the third piece.

03:02 So you can see, it starts from the origin of the replication and then go backwards, and then again, move.

03:11 Towards the replication form.

03:14 And eventually, these separate okadaki fragments will be connected together by ligation.

03:21 All right, so you can tell that the two strands are slightly different, but there is something in common.

03:29 So let's look at the following options.

03:32 First of all, it says that dna polymerase reads dna template from 5 to 3 direction, which is true for both cases.

03:41 For both leading and lagging strand, dna polymerase binds to the dna template and read it in from 3 to 5 direction.

03:51 So this is a true statement.

03:53 B, it's a significant cause of mutation, which is also true because when dna replication happens, it's not very sick.

04:02 A lot of time, a dna replication will have mutations are mismatch.

04:07 So certain nucleotide was replaced or substitute with other, a different nucleotide.

04:16 So a lot of time, the mutation are introduced by the inner replication.

04:22 So the second statement is also true.

04:24 Third statement, it has proofreading ability.

04:27 And this is also true because dna polymerase does have a self -corrupting process of proofreading.

04:37 So whenever there is a mismatch, dna polymerase is able to find a way to fix the mismatch, cleave it out, and then put in the new correct nucleotide.

04:49 That's also a true statement.

04:52 For d, it synthesized dna from three to five directions.

04:58 And this statement is wrong because when we look at the two newly synthesized strand, bottom, and the top and bottom, they're the same way...

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