Replicating structures in DNA can be observed using electron...

Replicating structures in DNA can be observed using electron microscopes. Regions being replicated appear as bubbles as shown in the diagram below: Assuming bidirectional replication, how many origins of replication are active in this DNA molecule? __________ How many replication forks are present? __________ Assuming all replication forks move at the same speed, which the origin of replication was activated last? ____ DNA replication in this organism occurs once every 30 minutes. The genome contains 3.2 x 10^8 base pairs. Eukaryotic DNA polymerases synthesize DNA at a rate of 75 nucleotides per second. Approximately how many origins of replication are required for this rate of replication?

Transcript

0:00 Hello students.

00:01 Now in this question they have given that there are many replication bubbles that are represented here.

00:08 If you see e, this is the replication bubble that you are seeing.

00:12 This whole thing that you see, there are two strands of dna that you see, right? so that is the replication bubble that you're observing.

00:20 It is starting at this particular point you're observing.

00:24 Carefully if you observe this particular region is the one that will be the replication bubble.

00:30 And if you observe carefully b is the one wherein you're observing it is so long right so you're observing that this is how it is right so now all we need to understand is that here basically we need to find the number of origin of replication if it is a bi -directional replication now if you observe carefully there are five replication bubbles right in this diagram they have given that there are five replication bubbles so origin of replication will be two right two in one replication bubble you will find so we can multiply five by two to get the value of ten so there are ten origin of replication in this particular instance right coming to the next question how many replication fork do you observe what is a replication fork is nothing but the replication bubble.

01:31 So we are observing five replication forks in this particular diagram.

01:37 Now the next question is that if we observe a replication fork which runs at the same speed, which origin of replication is activated the last.

01:48 To understand which is activated the last, all we need to do is identify the one that is the smallest replication bubble.

01:57 Right.

01:57 If we observe the b1, right, it is.

02:00 Is not a small replication bubble, it's so huge, right? c is a little bit small, but e is very long and d is also longer than c.

02:08 But if we observe a, a is the one that is the smallest.

02:12 So which is the one that is activated last? it is a that is activated last, right? so that is what we can mark our answer as.

02:22 Coming to the next question, here they are giving that dna replication takes 30 minutes, right? and they have given that the genome of eukaryotic dna is 3 .2 into 10 power 8 base pairs...

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