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Sep. 13th, 2015 11:40 amNormal cells are diploid.
One chromosome from each parent.
Germ cells are diploid.
Gametes are haploid.
Germ cells go through meiosis to become gametes.
Germ cells start out with 2 chromosomes.
Then they replicate.
Sister chromatids pair up.
Now tetraploid.
Non-sister chromatids can cross over (chiasmata/recombination)
Sister chromatids can also cross over, but no genetic significance.
Meiosis has 2 cytokinesis events.
Go from 2 chromosomes to 4.
The 4 fissions.
The two diploid cells fission again.
Then 4 gametes with different chromosomes.
When the haploid gametes meet up, then you get diploid offspring. With one chromosome from each parent.
Suppose mother has AB and ab.
Suppose father has AB and ab.
If on different chromosomes, would expect
One mother cell has 2 chromosomes. A and a (1) and B and b (2).
They replicate, then AA aa and BB bb.
They have different ways of fissioning: AA BB, AA bb, aa BB, aa bb.
Then they fission into haploid gametes.
Independent assortment says you're just as likely to end up with
AB, Ab, aB, and ab.
One mother cell has 2 chromosomes: AB and ab (1).
They replicate, then AABB and aabb in the same cell .
They're going to fission into AABB and aabb in different cells.
Then they're going to fission into AB AB ab and ab, without recombination.
Recombination would say you start out with ABAB and abab.
These non sister homologues would then cross over and you might get ABab and abaB in the same cell.
Then they would fission into two cells, one with AABb and one with aabB.
Then those cells could fission into AB, Ab, ab, and aB.
Meiosis I: a germ cell divides into 2 diploid cells.
Meiosis II: 2 diploid cells divide into 4 total gametes.
In both, cytokinesis occurs in telophase.
The chromosomes duplicate in meiosis I, giving rise to 2 sets of sister chromatids.
Each pair of sister chromatids is joined by a centromere.
During the first meiosis, sister chromatids travel together, and the centromeres remains joined.
During the second meiosis, the centromeres are separated so that the individual sister chromatids can go into individual daughter cells.
One chromosome from each parent.
Germ cells are diploid.
Gametes are haploid.
Germ cells go through meiosis to become gametes.
Germ cells start out with 2 chromosomes.
Then they replicate.
Sister chromatids pair up.
Now tetraploid.
Non-sister chromatids can cross over (chiasmata/recombination)
Sister chromatids can also cross over, but no genetic significance.
Meiosis has 2 cytokinesis events.
Go from 2 chromosomes to 4.
The 4 fissions.
The two diploid cells fission again.
Then 4 gametes with different chromosomes.
When the haploid gametes meet up, then you get diploid offspring. With one chromosome from each parent.
Suppose mother has AB and ab.
Suppose father has AB and ab.
If on different chromosomes, would expect
One mother cell has 2 chromosomes. A and a (1) and B and b (2).
They replicate, then AA aa and BB bb.
They have different ways of fissioning: AA BB, AA bb, aa BB, aa bb.
Then they fission into haploid gametes.
Independent assortment says you're just as likely to end up with
AB, Ab, aB, and ab.
One mother cell has 2 chromosomes: AB and ab (1).
They replicate, then AABB and aabb in the same cell .
They're going to fission into AABB and aabb in different cells.
Then they're going to fission into AB AB ab and ab, without recombination.
Recombination would say you start out with ABAB and abab.
These non sister homologues would then cross over and you might get ABab and abaB in the same cell.
Then they would fission into two cells, one with AABb and one with aabB.
Then those cells could fission into AB, Ab, ab, and aB.
Meiosis I: a germ cell divides into 2 diploid cells.
Meiosis II: 2 diploid cells divide into 4 total gametes.
In both, cytokinesis occurs in telophase.
The chromosomes duplicate in meiosis I, giving rise to 2 sets of sister chromatids.
Each pair of sister chromatids is joined by a centromere.
During the first meiosis, sister chromatids travel together, and the centromeres remains joined.
During the second meiosis, the centromeres are separated so that the individual sister chromatids can go into individual daughter cells.
