View Full Version : What is a gene?

20th October 2002, 09:59 AM
This is the title that I have been given for my disertation. Its a little vague to say the least. And it has to be in the first week after the christmas break! It's only 5000 words so its not to bad.

What I want to do is share some of my thought/extracts from the work I am doing in this forum and see what you guys think.

I thought that I would start with a look at the history of genes, Watson and Crick, Mendal, and the trouble Darwin had trying to fit his ideas about evolution into a coherent whole when he had no idea about genes (he thought that the genetic messages was 'blended' from the two parents, he did not realise that genes were passed on by discrete units). Then I will go into a more scientific approach i.e. GATC, trinucliotides(codons), introns and exons.

So to Start. At the most basic level a gene is evolutions ways of passing information down thorugh the geneartions (run faster/throw better etc). To look at genes in more detail it is best to study model species, things like rats, mice, yeast and arabidopsis. This is because they are easy to munipulate and reproduce. In a VERY simplified form each gene encodes one protein (not always true as some genes can produce multiple proteins through a process known as splicing). It was originaly thought that proteins must be what carried the information about how to build the body because no other set of molecules had enough varitiy to all the infomation needed. In modern times with computers running amazingly complex caluculations just using 0 and 1 it is much easier to see how just four neucleotides can be lifes code. In fact much of the genome is 'junk'and not used by the cell (triplet repeats, transposons and other parasite DNA), in fact up 97% is now considered to be junk. The other amazing thing about the genome is how consereved it is and how little changes can make a huge differnce, a few examples: we share 98% of our DNA with chimps, about 50% with bannans and many of the most essential genes are shared with yeast:confused: !

This has been a (very) breif introduction and more will hopefully follow. PLease reply with any questions/comments.

20th October 2002, 10:44 AM
Reminds me of my days at uni! :D

Cant wait to

I think your approach is pretty good, starting with the history and then going into functional details.

If you have questions down the road on specific parts, dont hesitate to ask, some ppl might know!


20th October 2002, 02:29 PM
Sounds like a good approach. I would love to read it when you are done.

21st October 2002, 11:39 AM
Part 2

The idea of the gene was first postulated by the Italian (or might have been austrian, will have to look that up) monk Gregor Mendal (circa 1900's). Through breeding experiments using mostly changes in the phisology of peas (smooth vs wrinkly, spotted vs plain) Mendal found that he was able to predict what the offspring would look like. In experiments lasting years and involving a large number of individual plants and characteristics Mendal finaly proposed a mathmatical formula that inabled him to predict the idea of genes as single units. This was a revolutionary idea as previosly it was believed that the code of the parents blended and so the offspring would be exactly a mix of the two parents. However this would mean that all children would be twins and distictive characters would be lost in relativly few generatios. Mendal saw another possibility that each character was a separate unit and these could be inheritid individualy. He also discovered the rules about how how each offspring only gets half the genteic information of each parent, i.e each parent is 2n, each sperm or egg is n therefore each new offspring is n+n=2n. Mendal also proposed the idea the genes have dominant and reccesive charateristics. So if a child has a brown hair allele (the gene is hair colour, but an allele is which colour that gene encodes) and a blonde hair allele then that child will have brown hair (ignoring the possibility of recombination and mutation which I will get into later, oh and dyeing is cheating). The child must inherit two blonde alleles for them to have blonde hair. Unfortunatly Mendals work was lost, the head of his order asked him to look a a particular plant (can't remember its name). The preoblem being that this plant reproduced asexually but needed pollen to start the reproductive cycle. Mendal could not work out how this plant reproduced and became disencahnted with his work until he gave up, his work on peas virtualy unknown. It was not for many years and after the publication of Charles Darwins book the origin of the species that Mendals ground breaking work was rediscovered. Imagine how much more accurate Darwin could have been if he new exactly how the code was pasted on. Dispite these set back (and the fact that Mendal had died before the full implications of his work was discovered) Mendals work remains one of the most amazing insights into the way in which genes work and what he discovered is still used in a practical way around the worl to this day.

Next time a bit of basic biochemistry,

wow I bet your realy looking forward to that one.

21st October 2002, 12:16 PM
Originally posted by fragallrocks

postulated by the Italian (or might have been austrian

I think he was austrian, yeah. Born in Heizendorf (Czech republic today).

Gregor Mendal

I believe its Mendel, not Mendal.

The child must inherit two blonde alleles for them to have blonde hair.

You start talking about alleles without actually telling anyone what it is. The fact is true but it maybe be good if you'd put a very short definition of an allele before this somehow :)

Next time a bit of basic biochemistry,

wow I bet your realy looking forward to that one.

Indeed :D

I'm not trying to pull your work apart, just trying to offer to help spot any "errors" I think might spoil the article!


21st October 2002, 12:21 PM
Did a bit of edits at Ragnarog (positive)surgestion. Can't be bothered to change every Mendal to Mendel but I think Ragnarog is right about the spelling.