00:01
In this question, we are looking at the growth of two cell lines, and specifically one that contains a loss of function mutation in the enzyme telomerase.
00:12
So in this question, we're just focusing on telomerase and what exactly its function is.
00:18
Also, this is on the basis of eukaryotic chromosomes, so just remember that.
00:26
So down below, i have our complementary base pairs of vicariotic chromosomes.
00:30
Dna strands comprising our double helix.
00:34
And in the process of dna replication, we know that we have something known as a leading strand and a lagging strand.
00:44
And on the lagging strand, we have rna primers at multiple different sites forming our okazaki fragments, which those are then eventually removed, and the rna primers are filled in with dna polymerase to fill in our nucleotides.
01:01
However, that rna primer that is left on the very end, due to the fact of dna's anti -parallel structure and the fact that nucleotides can only add to the free 3 prime end, there you're going to have a segment of dna, which i have drawn out down below here, this kind of segment here on your lagging strand, that is not able to complementary base pair with anything on the leading strand.
01:28
So essentially it's kind of extra nucleotides that are kind of left to hang.
01:34
And it's specifically actually called the 3 prime overhang for this reason.
01:40
And the ends of the chromosomes are known as your telomeres.
01:48
And telomeres are important because they serve as kind of caps on your dna.
01:54
So that through more rounds of replication and modification than processing afterwards, with each round of dna replication, essentially a little, bit of dna off the ends of your chromosomes is lost.
02:09
So to prevent this from being detrimental, because obviously we don't want important genes and gene sequences to be dissolved, we kind of have to add a little bit extra padding on the ends of our chromosomes.
02:24
And that is where telomeres come into play.
02:27
So telomeres are kind of extra nucleotides that add in that kind of protective cap on the ends of our chromosomes.
02:34
Chromosomes.
02:36
And they are formed with this three prime overhang with the help of the enzyme telomerase.
02:46
And pretty much what telomerase is or what it does is it itself is also an rna primer.
02:53
And it includes nucleotides that are going to complementary base pair with that three prime overhang.
03:00
And in most organisms, mammals, humans, that three prime overhang is going to be ttaggg.
03:08
Just kind of a, what's the word i'm looking for, kind of unanimous throughout the species.
03:16
So it can be easily recognized by the enzyme...