Still struggle with meiosis

[ladysmanfelpz]

Only gone through it about 400 times, but man these Mcat questions on it can kill me. I have the general process down, but when they go through different species at different stages I get quite confused even though it's the same concept. I guess it's the whole chromosome, chromatin, chromatid thing that gets me. I remember asking countless questions about this in undergrad and still never quite grasped it to useable knowledge. Crossover and stopping points along the process gets me as well. Sorry not the most thorough post, but I've been busy with the holidays and haven't been studying much lately. Anybody have a simple breakdown, memorization techniques, or other resources to help solidify this concept to not miss those guaranteed 2-3 questions on the topic?

Thanks everyone

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[Imperius]

Khan Academy helped me through life, here's a good watch on meiosis. Hopefully it helps:

 

[vivatix]

Only gone through it about 400 times, but man these Mcat questions on it can kill me. I have the general process down, but when they go through different species at different stages I get quite confused even though it's the same concept. I guess it's the whole chromosome, chromatin, chromatid thing that gets me. I remember asking countless questions about this in undergrad and still never quite grasped it to useable knowledge. Crossover and stopping points along the process gets me as well. Sorry not the most thorough post, but I've been busy with the holidays and haven't been studying much lately. Anybody have a simple breakdown, memorization techniques, or other resources to help solidify this concept to not miss those guaranteed 2-3 questions on the topic?

Thanks everyone

Post some specific questions that you had trouble with

 

[3member]

I totally get you, hopefully I can help out some. So a chromosome can be either a "I" or "X" if you get my drift.

But the difference btw the X and the I is pretty much replication.

I I --(replication)--> X X
Both I I and X X are a pair of homologous (homologues) chromosomes. That's why you have 46 chromosomes before replication and 46 chromosomes after replication. Aka humans have 23 homologous pairs.

Okay, now moving on to the chromatids spiel... so the other difference between I and X is obviously their shape! Though they are both chromosomes, the sister chromatids of the X are connected via the centromere. I guess the best way to illustrate the chromatids are )(
Each ) and ( is a chromatid. They form "X"

There's a chart I have that helps me out a lot (hopefully it'll help you too):

Replication
Start: Diploid (46 "I" Chromosomes)
End: Diploid with sisters (46 "X" Chromosomes)

Mitosis
Start: Diploid w/sisters (46 X, aka 96 Chromatids)
End: Diploid (46 I, since they divided)

Meiosis I
Start: Diploid w/ sisters (46 X)
End: Haploid w/sisters (23 X chromosomes, 46 chromatids--the Xes have divided)

Meiosis II
Start: Haploid w/sisters (23 X Chromosomes, 46 chromatids)
End: Haploid (23 Chromosomes, the ) ( chromatids have divided at the end of meiosis II)

Hope this helps somewhat and lemme know if you have any Qs! I'm embarassed to say it took me prolly 10 years after freshman year biology to really understand cell/gamete division haha...

 

[Necr0sis713]

Just remember this, and as long as you know mitosis you'll be way better off.

Meiosis I: splitting of homologous chromosomes; After this the cells are haploid (reductive division)
Meiosis II: splitting of sister chromatids; This is considered to be the same as mitosis

In all honesty, knowing your mitosis checkpoints will help TREMENDOUSLY. The wording can be tricky for these kinds of questions. For instance, if they ask "At what check point will the cell arrest if DNA is damaged?" you might see the word DNA and think "Ok, since there is the word DNA, the S phase is involved" and you might say S phase or G2...But, its in fact G1 because the cell does NOT want to replicate damaged DNA.