Upcoming Edexcel AS Biology: Unit 2 exam on 26 May 2011

7.7 for the average question anyone?

Reply 181

TheChief

Original post by 888jamie888

7.7 for the average question anyone?

Yes, that's what i put :smile:

Reply 182

Charlesworth

Original post by Hanz_a93

It was the last question...stuff about anti microbal properties and why some cellotape or something was needed to shut the lid..

Oh, I thought it was okay apart from the first part asking about how the bacteria is added or something. Honestly didn't have a clue!

(edited 12 years ago)

Reply 183

Charlesworth

Original post by 888jamie888

7.7 for the average question anyone?

yeah, pretty sure that is what I got :biggrin:

Reply 184

OP

Original post by Biology Freak

Noooooooooo your answer is correct it is 11000!! see all of them were switched off, and the question was asking which one of them is totipotent and it was 11000 because totipotent cells respond to most of the stimulus and since 11000 is the smallest number of unspecialised cells then this mean that it is totipotent GOT ME?!
So guys it is 11000

Original post by Biology Freak

Sorry to disappoint you guys but it was cell wall, and it wasn't already

Erm, firstly, totipotent stem cells have all their genes switched on, ready to make any type of cell, this is GCSE knowledge. If one single gene is deactivated, that means mrna can't be transcribed from it, a protein can't be made, and so the cell will not be modified in a specific way, and that's one less differentiated cell.

All genes must be switched on ready to make any type of cell. If you read the revision guide, active gene does NOT equal transcription, under the correct stimulus transcription will occur.

Secondly, LOL that wasn't a cell wall, click on this link and this link, and read out to me what it says for the final outside layer. Thanks. I don't know what disapointment you're talking about.

Reply 185

In the revision guide it says in stem cells, not all genes are expressed because not all of them are active. I was taught that when put under the right stimulus ( a chemical or whatever) more genes would be switched on which would code for proteins that would change the structure of the cell.

Reply 186

Great

thats good i mean for the question about the breed thing did you talk about natural selection and saying there can be a mutation in genes which could make them survive longer something like that? i wasnt sure on the bacteria where they labelled the capsule thing i put glycoprotein haha not sure

Reply 187

OP

Original post by 888jamie888

In the revision guide it says in stem cells, not all genes are expressed because not all of them are active. I was taught that when put under the right stimulus ( a chemical or whatever) more genes would be switched on which would code for proteins that would change the structure of the cell.

That revision guide has cost you marks. It should have quoted this as in my GCSE biology revision notes:

'Cells become specialised because the genes that are not required become switched off. Only the genes needed to make a particular type of cell work are left switched on.'

Reply 188

Great

so IS THE ANSWER 23000??

Reply 189

OP

Original post by Great

so IS THE ANSWER 23000??

1100000000000000000000%

Did anyone actually do GCSE Biology? :|

Think of it as a rainbow, you start off with all the colours, all the active genes, and then to end up with the colour you want, the type of cell you want, others are blacked out, i.e. switched off.

You have to start off with the whole spectrum of colours, you can't just get orange and blue materialize out of nowhere from black.

(edited 12 years ago)

Reply 190

OP

Original post by Great

But darling this is not gcse its a level and in our revision book it says 23000

I'm well aware this is a level, thanks, but if anyone really liked the subject they should have remembered such a fact from last year.

If the revision book says 23,000, great? Lol, this is old news.

Reply 191

Great

the last question did for the reliable one i put it is not reliable as they have only tested it with one bacterium ! i put they should have tried it with more bacteria which will make the results more accurate and reliable

Reply 192

croag

12

The only one I messed up was the egg blastocyst one. All the others were easy.

Reply 193

Well this came out of the CGP official Edexcel book and it's what our college has been taught. I'm going to trust an A-level book over a GCSE book especially when this is an A-level exam.
If all the genes were originally on then everything would be coded for and the cell would have all kinds of crazy structures.
Honestly turn to page 55 of the CGP book.

Reply 194

OP

Original post by 888jamie888

Well this came out of the CGP official Edexcel book and it's what our college has been taught. I'm going to trust an A-level book over a GCSE book especially when this is an A-level exam.
If all the genes were originally on then everything would be coded for and the cell would have all kinds of crazy structures.
Honestly turn to page 55 of the CGP book.

That wouldn't happen because the active genes are only transcribed by mRNA under the correct stimulus.

When genes switch off, they switch off forever, and cannot return to their active state, it is for this reason that cells become 'permanently' modified into e.g. a hair cell.

If genes could just magically switch on from dormancy, we would be able turn adult stem cells into embryonic stem cells. This is not the case, the process is irreversible in eukaryotes.

Reply 195

Again I'm going to trust the A-level book over your GCSE revision notes.
We'll have to agree to disagree.

Reply 196

JosephHoneywood

I put 23,000

Main reason is, if any of the genes were switched off, then they would never turn back on again thus making them not totipotent obviously.

When a gene is switched off, it is permanently switched off, so a totipotent has to have all of its genes switched on.

There is a difference from having the genes switched on, to having them actively expressed.

Nothing is being expressed, it is only until they start turning off that they begin to express.

So I am pretty damn sure it is 23,000.

Sneaky question by edexcel though...

Reply 197