Edexcel A2 Biology SNAB 6BI04 ~ 6BIO5 June 2016

Original post by LyreBirds

Yeah in the syllabus it comes under Topic 6:
4. Explain how one gene can give rise to more than one protein through post-transcriptional changes to messenger RNA.

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

Reply 762

Original post by Fuego1

What were the two substrate molecules for 1 mark? I guessed Rubp and co2 but surely co2 isn't a substrate since it's a gas??

thats exactly what i wrote and still think :biggrin:

Reply 763

IoMc

3

Original post by cmolloy12

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

ooh i kinda put that, haven't seen anyone say that. Thats kinda reassuring....

Reply 764

rory58824

2

Original post by cmolloy12

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

Really? The IAL January 2014 paper had a similar question if I remember.

Reply 765

setarcos

8

Original post by cmolloy12

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

Question wasn't specifically asking why they would be of different lengths, it was asking more abt how different proteins could made from a single gene so it is perfectly appropriate to discuss post transcriptional modifications. That will be one of the main points for definite. Also, genes were not different lengths, the proteins were, the gene coding for the different proteins was exactly the same.

(edited 7 years ago)

Reply 766

Original post by hopefuldentist10

Whoopsie, I didn't revise exons/introns. I spliced my score by 6 marks there.

Dropped maybe 20-25 marks in that paper, I have no idea. Just little marks here and there, eg. saying "cellulose is beta" instead of "beta glucose".

Considering many people thought it was an awful then the grade boundaries will get me on an A* hopefully. Hooray for dumbed down education.

you may be in luck for the 6 mark cos a key part of the question said the genes were different lengths which would lead to different primary sequences and therefore different proteins

Reply 767

Original post by cmolloy12

thats what i got for the % but i can't remember the other question what was it

It was the difference in the body temperature, which I calculated to be 1.23

Reply 768

Original post by greenorange

I did trophic level 3 divided by trophic level 2, after I subtracted total energy in from energy out.

yea it was 70/800 x 100 the method for this equation is in the revision guide

Reply 769

MrSheeple

I remember it saying different protein lengths, but not different gene lengths? Wouldn't be the first brain fart I made on that paper if so lol

Reply 770

Ladymusiclover

20

Original post by sssssshh

It was the difference in the body temperature, which I calculated to be 1.23

How many marks was that worth?

Reply 771

Original post by greenorange

I measured from the highest point to the lowest, maybe 1.75-I honestly can't remember.

yea thats what i did i think loads of people were caught out and measured greatest increase and not change

Reply 772

setarcos

8

Original post by MrSheeple

I remember it saying different protein lengths, but not different gene lengths? Wouldn't be the first brain fart I made on that paper if so lol

Nah you are right, his explanation was wrong, it wasn't genes of different lengths, it was proteins of different lengths, the explanation talking about post transcriptional modifications is correct.

Reply 773

Nemo9000

3

Original post by cmolloy12

yea it was 70/800 x 100 the method for this equation is in the revision guide

Im sure it asked about percentage availibe to level 4 from level 2 so it would be 70(energy available from level 3)/2300(energy in at level 2) x100 which is where we are getting 3% from.

Reply 774

Original post by Ladymusiclover

How many marks was that worth?

Not too sure, but I think it was 3

Reply 775

Ladymusiclover

20

Original post by sssssshh

Not too sure, but I think it was 3

I think the trophic level question was 3 marks but I thought the other calculation was max. 2 marks.

Reply 776

A.Francis

7

Original post by cmolloy12

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

I disagree with your point. I think post transcriptional changes would have been credited.

Reply 777

Original post by Ladymusiclover

I think the trophic level question was 3 marks but I thought the other calculation was max. 2 marks.

Yeah I think you're right.

Reply 778

Original post by cmolloy12

a lot of people fell into this trap and got dragged into talking about splicing but the key point was that the genes were different lengths and would therefore have different amino acids primary sequences, giving rise to different proteins

How do you propose different lengths of proteins are made aside from due to splicing and post transcriptional changes, if the same gene is used? I'm pretty sure they said the proteins were coded for by the same gene. Can't be entirely sure tho.

Reply 779

Moleyeyes