00:01
Hello students.
00:03
So today's first question is that during metaphase 1 and there is a blank.
00:07
So these are the different options where you have to tell what happens during the metaphase 1.
00:12
So tetrad form and crossing over occur.
00:15
No, this is incorrect option because crossing over occurred during the peccatin stage.
00:21
Crossing over occurred during the peccatin stage and this peccatine stage itself occurred during the pro phase.
00:28
To be specific pro phase one so this is not true now next is the sister chromatids separate and moves to the opposite pole when they start moving to the opposite pole then that is the anap phase stage that is the anaphase stage not the metaphase so this is also incorrect now nuclear envelop breaks up so this help happens in the during the initiation of pro phase initiation of pro phase so the remaining option that is d is our correct answer d is our correct answer which is a tetrad line up in the middle of the cell so what is it so during that phase what happens during meta phase suppose this is our cell, this is our cell and the chromosomes they line up like this.
01:27
They line up like this in the middle.
01:31
In the middle, this is the meta phase plate.
01:35
This is the metaphase plate where they line up during the meta phase one.
01:40
So, d is the correct answer.
01:43
Now moving on to the next question, which is how many chromosomes you expect in a cell if non -disjunction occurred during miosis.
01:52
So these are the different options and what is the non -disjunction? so non -disjunction is actually something that happens when the homologous chromosomes or sister chromatid.
02:06
Either it can be homologous chromosome or we can say they are sister chromatid and they fail to separate.
02:15
And they fail to separate.
02:19
They fail to separate at meta phase.
02:22
So what happened? it result in the abnormal chromosome number.
02:28
Result in abnormal number.
02:31
We can say abnormal chromosome number or abnormal number.
02:35
So what happens? so what happened during this phase is that if this is our cell, if this is our cell, and suppose this is the cell.
02:45
And it already has this much chromosomes that already have duplicated in during the s2 phase.
02:52
Now it is in the metaphase plate.
02:54
Now what will happen during the meosis one? during meiosis one when they arrange themselves like this.
03:04
They will arrange themselves like this at the anaphyze stage.
03:09
At the anaphyze stage when they have to separate at the poles, separate at the poles, separate at the poles.
03:16
So rest of these two chromosomes, rest of these two chromosome, they will stay at one side only.
03:24
They will stay at one side only.
03:26
So the meosis one anaphase and they are at the poles.
03:31
But during meiosis two, what will happen? now we are talking about the meiosis too.
03:37
Now during meiosis two, we know that the sister chromatids separate here...