SNAB AS driving me mad! Please help!

Ok I'm having to learn my AS text book by myself pretty much as I wasn't taught in classes. Teachers = fail.
Anyway, I was just wondering if people could explain these processes to me in their own words since the text book is just driving me insane.

Transcription
How are individual genes switched on and off?
Protein trafficking
Mitosis stages

I'll probably find more, I'm just working my way through the specification.
Thanks in advance, any help is really appreciated.

Reply 1

baidoobjhcl

gene switched on by RNA polymerase and transcription factors binding on the promoter region....this means transcription can now be carried out

protein trafficking...proteins synthesised on ribosomes on RER...proteins send to golgi where there are packaged and put into vesicles...out the cell by exocytosis to where protein is required

mitosis...4 stages, prophase,metaphase,anaphase,telophase

Reply 2

*Rachie*

baidoobjhcl

Thanks; I finally managed to decipher the text book and googled a few things as well :biggrin:

Reply 3

Olibert

*Rachie*

Transcription - DNA strands unwind in the nucleus acting like a template. Free RNA nucleotides line up along side complimentary bases to form an mRNA molecule which eventually leaves the nucleus and works with translation in the ribosomes

Gene Switching - Genes are usually turned on or off when they are in certain mediums. E.g:

Ecoli produces Beta - Galactosidase which breaks down lactose into the monosaccharides. If the cell is in the presence of lactose, a molecule of lactose binds to a repressor molecule preventing it from binding to the DNA.

If there is no lactose in/around the cell, the repressor molecule binds to the DNA preventing transcription from taking place.

There is a good diagram on page 123 of the SNAB book.

Protein Trafficking -

1. Protein mRNA molecule is made in the nucleus
2. mRNA moves out of the nucleus and onto the ribosomes where the protein is made (Translation)
3. Protein moves through the rough endoplastic reticulum folding into a 3D shape.
4. Vesicles pinch of the RER containing the protein.
5. These vesicles fuse with the Golgi Apparatus
6. Proteins are modified in the GA
7. Proteins pinched off the GA in secretory vesicles.
8. Vesicles fuse with the cell surface membrane releasing the protein.

Mitosis - I remember it this way

There are two main parts -

1. Interphase
2. Mitosis

During interphase new cell organelles are made, mitochondrion etc.

During mitosis you get a whole load of other crap going on:

Straight after interphase:

1. Prophase - Chromosomes condense, centrioles move to opposite ends of the cell to form spindles

2. Metaphae - Break down of the nuclear envelope

3. Anaphase - Centromeres split, spindles shorten pulling the chromatids to the poles

4. Telophase - The newly formed chromosomes unravel and the nuclear envelope reforms

Cytoplasmic division now happens making two cells.

Interphase starts again

Reply 4

style

I know this is kind of thread hijacking but whats DNA polymerase?

Reply 5

gyrase

style

I know this is kind of thread hijacking but whats DNA polymerase?

Its the type of stick that polar bears chew on

Reply 6

*Rachie*

Lol - RNA polymerase is an enzyme which must combine with transcription factors onto the promoter region to make the transcription initiation complex, which switches on a gene and enables transcription to begin.
It also joins the RNA nucleotides to form the mRNA during transcription.

Edit - Just realised you asked for DNA nor RNA... am not sure about DNA polymerase :s-smilie: