00:01
We have a sample of dna.
00:02
15 % of the bases are thymine.
00:06
So thymine, 15%.
00:07
We want to know what percent is cytosine.
00:11
So let's write out the other bases.
00:13
There are four bases in dna, thymine, adenine, cytosine, and juanine.
00:18
How can we work out these other percentages from just thymine? well, first of all, these are all of the bases.
00:25
So if we add up their frequencies, like this, we will get 100%, because every base is one of these four.
00:35
So that's one equation.
00:38
Next, let's look at the structure of dna.
00:41
Dna is double -stranded.
00:43
So if i have a thymine and acytazine on this strand, i know i'm going to get an adenine and a guanine on this strand.
00:53
Because of base pairing rules, you always find them together.
00:57
So these are the strands, and they are bound to each other...