[kimmey]

can anyone explain to me why the cross for the bread wheat cross thing results in a sterile hybrid. what does sterile mean in this context ?

[The Illuminati]

(Original post by kimmey)
can anyone explain to me why the cross for the bread wheat cross thing results in a sterile hybrid. what does sterile mean in this context ?

sterile means won't be able to reproduce. this is usually due to polyploidy so bivalents won't be able to be formed at meiosis and with no gametes you won't get babies (sexually anyways)

[tamitm]

It might sound stupid, but do we have to say the exact words that are on the mark schemes (unless underlined), or it can be difficult!
I seem to be loosing marks just because i don't use the right words, but the context is correct!

[otrivine]

guys how would you describe the breeding of wheat is it all the numbers diploid we have to remember /?

[DoctorVertigo]

(Original post by otrivine)
guys how would you describe the breeding of wheat is it all the numbers diploid we have to remember /?

Don't think we need to know it in detail. It produces sterile offspring, due to odd number of chromosomes, homologous pairs don't form a bivalent, meiosis fails.

[DoctorVertigo]

(Original post by tamitm)
It might sound stupid, but do we have to say the exact words that are on the mark schemes (unless underlined), or it can be difficult!
I seem to be loosing marks just because i don't use the right words, but the context is correct!

I should hope not! I think you just have to make the same points

[otrivine]

which paper was the hardest ? was it the Jan 2011 paper

[hash007]

Can someone explain genetic drift?

[racheatworld]

Guys, in automated gene sequencing/interrupted PCR - do you use electrophoresis before you sequence the BAC gene or after? I don't understand why you'd need to use electrophoresis at all, because the laser and computer will arrange the fragments in order using the fluorescent colour information and which ones overlap?

[dks.]

what main topics does everyone think will come up?

[zmzm]

(Original post by racheatworld)
Guys, in automated gene sequencing/interrupted PCR - do you use electrophoresis before you sequence the BAC gene or after? I don't understand why you'd need to use electrophoresis at all, because the laser and computer will arrange the fragments in order using the fluorescent colour information and which ones overlap?

You need electrophoresis to work out what order the fluorescent fragments go in. I don't think there is any way of the computer just knowing what colours and sizes each fragment are. You need to use electrophoresis to put them in size order, THEN a computer will work out the sequence based on the sequence of colours.
At least this is my understanding of it, anyone correct me if I'm wrong?

[zmzm]

(Original post by sumsum123)
Adrenocorticoid is a hormone that causes corticosteroid hormones to be released from the adrenal cortex .

Danke!
rep when I have some

[whc23]

(Original post by hash007)
Can someone explain genetic drift?

Genetic drift is the change in the frequency of an allele in a population caused by the random transmission of alleles to the next generation. By chance, some of the time, one allele may be transmitted at a higher rate to the next generation. In the generation after that, there will be a greater chance of that allele being transmitted again since it is at a higher frequency in the parent population. After several generations, one allele can become fixed in a population and another allele completely lost.

http://cambridgeacademic.blogspot.co.uk/

[Fitter]

I've been wondering as i revised cloning then looked at the Galapagos islands - Is it possible, to use Nuclear transfer to clone Lonesome George? Using a body cell from him and putting it into an enluceated embryo? Or does this method only work with same species?

Ta

[racheatworld]

(Original post by zmzm)
You need electrophoresis to work out what order the fluorescent fragments go in. I don't think there is any way of the computer just knowing what colours and sizes each fragment are. You need to use electrophoresis to put them in size order, THEN a computer will work out the sequence based on the sequence of colours.
At least this is my understanding of it, anyone correct me if I'm wrong?

So do you use electrophoresis once you've cut up the BAC gene with restriction enzymes, then do interrupted PCR on all of the different sized fragments, then the computer will work out the sequence using fluorescent colours of terminator bases?

[zmzm]

(Original post by Fitter)
I've been wondering as i revised cloning then looked at the Galapagos islands - Is it possible, to use Nuclear transfer to clone Lonesome George? Using a body cell from him and putting it into an enluceated embryo? Or does this method only work with same species?

Ta

Lmao I think you need an enucleated egg cell from the same species. But even if they did make it work you would end up with a whole load of male tortoises... not very useful :P

[Fitter]

(Original post by zmzm)
Lmao I think you need an enucleated egg cell from the same species. But even if they did make it work you would end up with a whole load of male tortoises... not very useful :P

Poor George

[racheatworld]

(Original post by zmzm)
Lmao I think you need an enucleated egg cell from the same species. But even if they did make it work you would end up with a whole load of male tortoises... not very useful :P

You don't actually need an enucleated egg from the same species, in my notes nuclear transfer is done using a donor egg from one species of sheep and an enucleated egg from a different species of sheep. Lonesome George is a Pinta tortoise (from Pinta island), so you could use an enucleated egg from the female tortoises that are being conserved on other islands of the Galapagos - such as Isabela or Santa Cruz.

[zmzm]

(Original post by racheatworld)
So do you use electrophoresis once you've cut up the BAC gene with restriction enzymes, then do interrupted PCR on all of the different sized fragments, then the computer will work out the sequence using fluorescent colours of terminator bases?

Oh I didn't know restriction enzyme was involved I thought it was:
-single stranded DNA in solution with primers and nucleotides (some of which are fluorescent
-interrupted PCR takes place so you have diffferent lengths of double stranded DNA, each with their own coloured marker at the end which causes DNA polymerase to be 'thrown off' and stop addind nucleotides.
-Strands are separated by electrophoresis then
-run through a machine which reads them in size order (now they have been separated) and diplays the sequence of colours and therefore bases.

[zmzm]

(Original post by racheatworld)
You don't actually need an enucleated egg from the same species, in my notes nuclear transfer is done using a donor egg from one species of sheep and an enucleated egg from a different species of sheep. Lonesome George is a Pinta tortoise (from Pinta island), so you could use an enucleated egg from the female tortoises that are being conserved on other islands of the Galapagos - such as Isabela or Santa Cruz.

Oh good point. But won't they be too different from LG for it to work? What with the islands being separate so speciation occurs...