Need help with Genes/DNA;

[Z0rr0]

I'm stuck on three questions. I've written an answer for each but I don't know if they are correct.

Q3. b) Describe the structure and function of a gene.

A gene is a section of a DNA strand which carries instructions for a specific function. Genes hold information to build and maintain cells. Genes also pass genetic traits to offspring.

(Is this a suitable answer? I'm afraid I haven't really covered the structure part of the question. I'm having trouble with it.)

Q6. Why is it that some of the information on a DNA molecule must be “translated into proteins” in order to direct the activities of the cell?

They must be translated into proteins to make mRNA and amino acids.

(Is this too vague, or is it alright for an answer? If I need to expand on it, what should I expand on it with?)

Q7. Explain why the genetic code must be made up of codons that are at least three bases long.

The bases must be three bases long so the Ribosome can attach itself to the genetic code and produce an amino acid.

(Is this right? I'm pretty sure it is but I'm just checking.)

[Harvey23]

Hi,

Q3 seems fine. Although just to nitpick, a gene carries the information required to manufacture a single protein (in eukaryotes). This will not neccessarily function unless other proteins are also manufactured. In the case of enxymes, co-factors etc.

Your answer to Q6 is a tad wrong. Proteins are polymers of amino acids and dont make mRNA themselves. Im not really sure what the question is trying to get at, but ultimately DNA is translated into proteins BECAUSE they direct the acitivites of the cell. Why this happens is just a product of evolution...

For Q7, codons are three bases long because it makes available many different possibled codes. If genes were made up of a sigle nucleotide, only 4 amino acids could be polymerised at the ribosome. On the other hand there aren't enough amino acids to warrent genes made of 3+ nucleotides. Its a balance that has been conserved through evolution.

Hope this helps a bit

[canalon]

Q6: DNA is copied to mRNA which will be translated to protein by the ribosomes. so your answer is wrong. I thik what the question wants you to think about is how the essential chemicals reactions are carried out in the cell (hint: not by the DNA) and in a way to emphasize the difference between a plan to build a mchine and the machine itself, to use a metaphor.

Q7: see above, remember ther are 20 amono acid plus a need for at least one stop signal. The number of possible combinations for a codon of size n is 4^n.