biology help on a questionWatch
can someone please help me with this question please not sure what to write.
You sure know how to stimulate my nerdy brain haha!
OK mitosis just involves splitting of the nucleus into two daughter nuclei, then the cell divides into two. It has four main stages: prophase (first stage: MEMORY AID: pro = first as in prototype e.g. the first trial model of a car - if you have a bro, ask him (we boys are mad about cars!)); metaphase; anaphase and last telophase (Greek tel = far OR end AS IN telephone [talking to someone far away OR telescope [looking far away]). Look up some diagrams by googling OR a good website is mrothery.co.uk.
So after fertilization (fusion of male sperm and female ovum) to make a zygote, MITOSIS is what creates 2, then 4, then 8, then 16, then 32, then 64, then 128 cells to gradually make the zygote grow into a small collection of cells and eventually a baby.
NOW LET US TAKE MEIOSIS: Ok you know that a normal human cell has 23 pairs of chromosomes so total 46, of which two are the sex chromosomes (XX in females and XY in males).
What would happen if the male and female sex cells each had the 46 chromosomes and then they fused? Yes, well done the zygote would have 92 chromosomes, and instead of a baby, an alien from outer space would be born (kinda! ).
So to keep the NORMAL 46 chromosomes per cell in the baby, we need to make 23 each in the sex cells so that when they unite, you have the normal 46, still with me? YES YOU GOT IT! That is the purpose of meiosis. It consists of:
prophase I, metaphase I; anaphase I and then telophase I followed by:
prophase II, metaphase II; anaphase II and last telophase II.
HAPPY SO FAR? Good! If still crying, go and listen to "Happy" by Phil Pherell; see you in 2.5 minutes!
In the first division of MEIOSIS, the individual halves (chromatids) of the chromosomes DO NOT SEPARATE - RATHER WHOLE chromosomes move to each pole [half each], so each daughter cell has 23 now instead of 46 - THEN, in the 2nd division, it is exactly the same as in mitosis. How clever is that? I am an atheist, but Jesus was not stupid for those who believe in him. ().
Also google "independent assortment of homologous chromosomes"
"crossing over"; these two processes, in addition to random fertilization and mutation, are the basis of variation, which explains Darwin's theory of evolution through natural selection.
Finally go through my attached Powerpoint file to make all this stick in your mind.
PS I need to make some sausages, burgers, eggs and bacon now [it is not only cars we guys like] - so goodbye!