00:01
Okay, so let's start with question number 11 here.
00:05
And it's asking where the nucleus is intact during all of which phase.
00:14
Well, it's going to be that pro phase where your main function of this phase is for chromosomes to condense.
00:33
That's the main function of that phase.
00:38
And that's why the nucleus is still intact, because once you move on to metaphase or even pro -metaphase, the nucleus disappears.
01:07
So let's look at number 12.
01:08
12 is a little bit harder.
01:09
You counted a thousand cells.
01:13
Two one of those cells are in mitosis.
01:16
Okay, so 200 in mitosis.
01:22
So you can assume that 20 % of their time is spent in mitosis.
01:35
Now, of the remaining, we have 400 that have unreplicated dna, it's just x.
01:56
We have 250 of 2x.
02:00
I'm not going to write it down, and we have 150 of between x and 2x.
02:05
This unreplicated dna, that's going to be the g1 phase.
02:09
Right because if you have x to 2x you're going to be s phase and if you're going to have 2x you're going to equal g2 right so this is going to be g1 phase notice that 400 is double 200 just notice that real quick now we're told that mitosis of the cell cycle lasts two hours right so so if we know that mitosis is two hours and g1, that's not a g1, g1 is two times mitosis, we know that g1 must be four hours.
03:18
And that is your answer right there.
03:23
Awesome.
03:23
So now let's look to 13.
03:26
We're asked about prophase of myphs.
03:33
Mitosis.
03:36
And we're asked how many chromosomes are present? and we're given 2n equals 12...