Meiosis - aqa biology as level

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woah chill your beans, enough of the superiority complex, if you get THAT annoyed about someone asking then go to another thread!
However, you were quite helpful in an aggressive arrogant way.

Reply 21

MGIL

GonazGirl

woah chill your beans, enough of the superiority complex, if you get THAT annoyed about someone asking then go to another thread!
However, you were quite helpful in an aggressive arrogant way.

Sorry it's just like an infectious case of ''I don't get meiosis'' everyone's had it :yep:

Reply 22

GonazGirl

MGIL

Sorry it's just like an infectious case of ''I don't get meiosis'' everyone's had it :yep:

all been there! I got it the first time round when taught it as well, grr, why did i have to forget it! :mad:

Reply 23

Ejit

MGIL

why so harsh?

I don't like pharmacologists.

It seems a fair statement to me, I'm not saying she can't do it or anything; sure she's very capable, but it's a topic I would have expected an applicant to be familiar with.

:p:

Reply 24

MGIL

Ejit

how about pharmacists? :sad:

Reply 25

Zoology_Student_x

Meiosis.

in meiosis 1, dna has been replicated - interphase - '4n' chromosones.
undergoes PMAT and produces 2 cells with '2n' chromosones.
the homologous chromosones are now in separate cells
(remember independant segregation!!)

meiosis 2, there is no interphase process so the homologous chromosones do not replicate.
undergoes PMAT again, produces 4 cells with a chromatid in each.
ie, 'n' chromosones.

:biggrin:

Reply 26

chocoholic786

Im still confused LOL sorry can't help it i've been trying for ages now to grasp it but it aint working
so basically interphase happens the parent cell with 46 chromosomes replicates, is this now 92 chromosomes?
Then the pairs line up in the middle and are pulled apart so they have 46 in each?
then the chromatids are separated so this makes it 23 in each of the 4 daughter cells?

Reply 27

calender1994

do aqa just use past paper questions? or does anione have a teacher who is an examiner for aqa biology :P

Reply 28

Bevin

Original post by MGIL

Argh so many people don't get it!

Ok for the gazillionath time

| is a chromosome

| replicates to X during Interphase/s phase.

You now have 46 of X instead of what you originally had which was 46 of these |

What you originally had -46 of these |-were also called chromosomes despite only having one little |
And also after replication you STILL HAVE 46 CHROMOSOMES-X-called the same thing!

With the X type of chromosomes you call both the two sticks in the X a chromatid-so the X consists of two chromatids.

OK what next-mitosis or meiosis?

Talk about meiosis

After the first meiotic division you get 23 of X in each cell
so two cells with 23 X in each

After the second meitoic division you get the chromatids in X separating to give 4 cells of | with 23 of | in each
Again although you have | it is still called a chromosome
Thus after both meiotic division the cells are haploid
However the examiners wants you to understand that it is after the first meitotic division that the cells become haploid.

Does that make sense?!?!!!

Nope I still don't understand Meiosis at all

Reply 29

Bhavika22

Original post by Bevin

Nope I still don't understand Meiosis at all

Maybe i can helps, mieosis is where the homologous chromosomes are replicated so that there are 2 sister chromatids and in mieosis one the homologous chromosomes arrange themselves at the equator randomly and then the cell divides so that the two cells have an equal number of chromosomes one from each homologous pair. Hence after meosis one we have two daughter cells. Meiosis 2 will enable the centromeres to replicate so that the sister chromatids split up into two and the cell divides with a sister chromatid in each. Thus, we are left with 4 daughter cells 😊 i hope this helps!

Reply 30

hum1

Im gonna sum all the points we need for meiosis in the simplest way as we are just getting far too confused and are overcomplicating it
Ok so Meiosis is the process where 4 daughter nuclei form each with half the number of chromosones of the parent cells.
Main purpouse of meosis is for genetic variation otherwise we would all be the same, and to form haploid cells. This is to ensure during fertilisation when the gametes fuse the diploid number of chromosones is restored.
Two causes of varitaion in meiosis, Crossing Over by recombination and Independent Segregation of Homologous Chromosos

In crossing over, different equilation portions of chromatids exchanged, therefore different alleles exchanges to form a new variation ...
Independent segregation
Homologous chrmosones allign randomlu, results in genetic variation, maternal and paternal gammetes that mix during fertiliastionis random so therefore genetic variation, KEY WORD RANDOM , PAIRING IS RANDOM, GOING INTO TO PRODUCE OFFSPRING IS RANDOM

Now finally stages of meisosis
SONT OVER COMPLICATE IT

Homologous chromosones pair up, chromatids wrap around each other , this creates tensios, echanging of chromatids via crossing over

Second Stage - chromatids move apart 4 cells produced, half the number of chromosones of parent cells, basically gammeted

Key Words- Locus- position of a gene on chromosone or DNA molecule
Allele- A different form of the same gene
Gene- Section of DNA codes for dorming polypeptides

AS YOU CAN SEE THIS IS ENOUGH INFORMARION FOR MEIOSIS DON'T OVER COMPLCATE IT ANY MORE PLEASE LEARN THIS AND THAT'S IT...