I'm a bit confused about genes

I'm just wondering: if a protein has a quaternary structure, are all the polypeptide chains that it consists of coded for by a single gene? All of my AS bio textbooks define a gene as the code for a polypeptide. However, a protein such as haemoglobin consists of more than one polypeptide chain. Would I be wrong to say in an exam that a gene codes for a protein rather than a single polypeptide?

Thank you :smile:

Reply 1

smd4std

http://en.wikipedia.org/wiki/Gene

curtsy of Wikipedia

Reply 2

SnakehipsTTC

Technically yes, but I'm not sure if they would penalise it. 2 genes code for haemoglobin, and are both adjacent to each other on DNA.

(edited 11 years ago)

Reply 3

The Illuminati

Original post by Ggdf

At A level you can get away with saying either....I think

Reply 4

thegodofgod

Original post by The Illuminati

At A level you can get away with saying either....I think

I asked my teacher (who's also the head of biology at my school) about this exact question, and she e-mailed AQA for clarification - the reply was, that if you define a gene as 'A length of DNA that codes for a polypeptide', you'll get the mark, however, if you define a gene as 'A length of DNA that codes for one polypeptide', you won't get the mark. :lolwut:

Personally, I would interpret 'a' and 'one' as one and the same thing, but AQA apparently don't... :wtf:

Reply 5

Cirsium

Original post by thegodofgod

Personally, I would interpret 'a' and 'one' as one and the same thing, but AQA apparently don't... :wtf:

AQA are talking rubbish... obviously their opinion matters, since they're the ones writing the mark scheme, but that doesn't make any sense, and would be wrong even if it were... (Besides which, a gene can code for several polypeptides on the basis of alternative splicing!)

Reply 6

The Illuminati

Original post by thegodofgod

Personally, I would interpret 'a' and 'one' as one and the same thing, but AQA apparently don't... :wtf:

WTF, last time I checked a and one were practically interchangeable, that's ridiculous. I guess it's a good thing that I never say one and always say a....it's even better that I don't do AQA :tongue:

(unless OCR are that cruel too, which tbh they probably are)

(edited 11 years ago)

Levi's are the best.

Original post by Blackburn_Allen

Levi's are the best.

hahaha.

Reply 9

thegodofgod

Original post by Cirsium

AQA are ~~talking~~ rubbish...

Original post by The Illuminati

WTF, last time I checked a and one were practically interchangeable, that's ridiculous. I guess it's a good think that I never say one and always say a....it's even better that I don't do AQA :tongue:

(unless OCR are that cruel too, which tbh they probably are)

Don't worry - no exam board is as bad as AQA... :moon:

Original post by Blackburn_Allen

Levi's are the best.

Shame that DNA helicase / polymerase don't work on them - can't replicate the genes and make a fortune :ahee:

(edited 11 years ago)

Reply 10

qiaoyu.he

Original post by dmccririck

Technically yes, but I'm not sure if they would penalise it. 4 genes code for haemoglobin, and are all adjacent to each other on DNA.

Really? I thought that haemoglobin had 2 identical alpha subunits and 2 identical beta subunits? Is it not a waste of coding region to have 4 genes next to each other?

Reply 11

SnakehipsTTC

Original post by qiaoyu.he

Really? I thought that haemoglobin had 2 identical alpha subunits and 2 identical beta subunits? Is it not a waste of coding region to have 4 genes next to each other?