AQA A2 BIOL5 22nd June 2012

Quick questions, i dont know if im phrasing this question properly, but what is the advantage of sticky ends, when cutting dna and a plasmid using same restriction enzyme?

I would say the sticky ends have complementary bases, in that the sticky ends on DNA will be complementary to the sticky ends on a vector (plasmid)

I know it seems an easy question, but i just want to get the principle right, and also to word it correctly. Thanks

Yeah thats correct, hence the unpaired bases at ends(hate saying sticky ends lol) of isolated gene and vector/plasmid, will hybridise. We then use DNA ligase to reform the sugar-phosphate backbone, to form our recombinant DNA :biggrin:

Reply 981

swiftylol

18

Original post by EffKayy

Energy transfers, uses of inorganic ions, ATP - could come up as the essay.
Any other ones most likely to come up?! Need to practice..

I just did one on proteins, think that's likely aswell.

Reply 982

NinjaRikki

5

Original post by Bright.Inspiration.

off topic but... 810 in AR in the ukcat?! Bloody hell well done!

Don't ask me how I got it :smile:

I just practised looooads :smile:

Reply 983

NinjaRikki

5

Original post by JJMick

You retook unit 2 after getting an A?! Bloody hell.
I got 100 in unit 2 last time, was disappointed. I feel after my resit though it went really well - last question was a strange question though.

It's weird how you need exactly the same as me in unit 5 :tongue:

Doing medicine? Nice one I was going to do that but I will prefer being a scientist - less stress :smile:

Some could argue that being a Biomedical scientist is more stressful than being a doctor :wink:

Reply 984

umair.khan

Original post by NinjaRikki

Yeah thats correct, hence the unpaired bases at ends(hate saying sticky ends lol) of isolated gene and vector/plasmid, will hybridise. We then use DNA ligase to reform the sugar-phosphate backbone, to form our recombinant DNA :biggrin:

Thanks for the reply, hmm your ending just puts the icing on the cake lol :smile:

(edited 11 years ago)

Reply 985

ecokid

1

How are people dealing with the cycles involved with respiration or photosynthesis for an ATP type question? It's tough to find the balance between having enough detail to show the complexities of the cycle VS paragraph becoming too detailed and bloated as it sounds like regurgitation of info? Is it best to just focus on the requirements and the main ATP cycling areas? Cheers!

(edited 11 years ago)

Reply 986

JJMick

9

Original post by NinjaRikki

Some could argue that being a Biomedical scientist is more stressful than being a doctor :wink:

Nah

. I am hopefully going to go into research anyway :smile:

Reply 987

JJMick

9

Original post by EffKayy

Energy transfers, uses of inorganic ions, ATP - could come up as the essay.
Any other ones most likely to come up?! Need to practice..

Original post by swiftylol

I just did one on proteins, think that's likely aswell.

Yeah those seem likely; also how cells are adapted for their functions could be one.

Reply 988

I.LoveSyria.Aleppo

14

in how much detail do we need to know the nutrient cycles?
like if they ask describe nitrification ammonification etc, is it sufficient to just write the conversion of ammonium compounds into nitrogen compounds, that plants are able to take up?

help?

Reply 989

cutie_tootie

5

Hey!
Can anyone explain how oestrogen controls gene expression?
I keep finding different explanations and it is really confusing me :biggrin:

Thank you muchly!!!

Reply 990

R J

1

Original post by cutie_tootie

Hey!
Can anyone explain how oestrogen controls gene expression?
I keep finding different explanations and it is really confusing me :biggrin:

Thank you muchly!!!

1. Oestrogen, like all steroids hormones, is a lipid, so crosses the cell membrane by lipid diffusion and
enters the cytoplasm.
2. Oestrogen binds to its receptor protein (called ERα) in the cytoplasm to form a hormone-receptor
complex. This complex is now a transcription factor.
3. The active transcription factor diffuses into the nucleus through a nuclear pore.
4. In the nucleus the transcription factor binds to a specific base sequence on a DNA promoter, upstream
of RNA polymerase.
5. This binding stimulates RNA polymerase to transcribe genes and so stimulates protein synthesis.

Reply 991

koslni

5

Does anyone know where i can get relevant past papers??? is there only the 2 on the aqa website?? or am i missing some treasure trove of them somewhere

Reply 992

tomkeys

2

Original post by BodybuildinPassion

Can someone tell me the marking points for transcription/translation?

I have some for translation from a paper from the old specification, if that helps:

1. mRNA leaves (nucleus) through nuclear pore;
2. To ribosome;
3. tRNA molecules bring amino acids (to ribosome);
4. Specific tRNA molecule for specific amino acid;
5. Anticodon of tRNA corresponds/complementary to codon on mRNA;
6. Peptide bonds form between amino acids
7. tRNA detaches and collects another amino acid;
8. Ribosome moves along mRNA;

I'll throw a few ideas out there for transcription, too:

(Assuming we are ignoring transcriptional factors)

1. RNA polymerase binds to promoter sequence
2. DNA helicase catalyses breaking of hydrogen bonds in DNA to expose template sequence
3. Free RNA nucleotides bind to exposed DNA base sequence through complementary base-pairing
4. RNA polymerase catalyses formation of phosphodiester bonds (not required, I think) between RNA nucleotides
5. RNA polymerase moves along template strand
6. RNA polymerase detaches once stop triplet reached
7. pre-mRNA released

Then you have splicing and so on.

(edited 11 years ago)

Reply 993

tomkeys

2

Original post by koslni

Does anyone know where i can get relevant past papers??? is there only the 2 on the aqa website?? or am i missing some treasure trove of them somewhere

One specimen paper and two past papers. You might want to try the old specification's past papers, there is much that is relevant on them (even though the style of the exams has changed quite a bit). You'll find essay questions on them, too.

Reply 994

cutie_tootie

5

Original post by R J

1. Oestrogen, like all steroids hormones, is a lipid, so crosses the cell membrane by lipid diffusion and
enters the cytoplasm.
2. Oestrogen binds to its receptor protein (called ERα) in the cytoplasm to form a hormone-receptor
complex. This complex is now a transcription factor.
3. The active transcription factor diffuses into the nucleus through a nuclear pore.
4. In the nucleus the transcription factor binds to a specific base sequence on a DNA promoter, upstream
of RNA polymerase.
5. This binding stimulates RNA polymerase to transcribe genes and so stimulates protein synthesis.

Ah hah! Makes sooo much more sense now! Why can't text books write things simply?! Thank you very much for your help! :biggrin:

Reply 995

Fazzting

Original post by James A

you need to leave your self 40 minutes for the essay + planning.....

The exam in total is 2 hours 15 minutes, so you must finish the questions from the paper, 1 hour 35 minutes into the exam to give yourself time for the essay :tongue:

thankyou!

Reply 996

JJMick

9

I am praying that the protein essay pops up! :P