Human Genetics

DaSilva

I'll start off saying that I have never studied Biology past junior cert level. With the abundance of pop/junk science these days it's hard to know what I read has any credibility. So my question is about Genetics, not Nature v Nurture, but rather Environment v Genetics.

I recently started thinking about inherited traits and their affect. I read a lot "new gene found too influences X" and I think wow that's pretty amazing, how do they find that out? "...Dr.Biology looked at the various forms of the gene coding in YYY number of people...and found that ZZ% of cases...". Uh oh, wait a minute you are establishing cause of (behaviour / physical attribute) by a single gene in a sample size of YYY (often a few hundred). First off, what about all the other factors at play? Have all the sample subjects had any sort of similar lives? What about plain old statistical variance, very possible in a small sample size?

What I'm getting at is, carry out the same test to find the same result on the same sample of people, but instead of linking it to a specific gene, link it to something else, like the social/economic status of the subject or even their tendencies towards porridge or corn flakes for breakfast.

I'm trying to establish a rough idea on genetics impact on people and whether it is negligible. Compare a child with an inactive lifestyle but with excellent genes, and an average genetic child with an intensive training regime, and after a few years see who is faster / stronger etc.

Ok, so that's an extremely exaggerated example, but what do good genetics grant? A greater capacity to improve? I'm just finding it hard to gauge genetics impact in certain areas such as sport or intelligence.

Red Hand

Many such articles are speculative and use lots of "may" in them.:) I would assume that the few hundred people and the proposed genetic link to some disease/genetic advantage is only the first step, sort of like a clinical trial involving testing a new drug?

The usual set up in testing a new drug goes:

Step one: Test on animals to see if harmful

Step two: Test on small group (around 20-80 volunteers)

Step three: If not harmful, then test drug on an appropriate group ie someone that suffers from a condition that drug will hopefully treat, around 500 people.

Step four: Again, if it looks promising, then go to larger scale-usually to 4500-6000 people for full clinical trial over a period of maybe 4 years, involving double blind placebo. Then use statitics to see if there a link between patient improvement/deterioration and the new drug.

I'm sure there would be something similiar for matching specific genes and gene sequences. A major part, as you say, would involve the sample size of the population and the statistical models involved. Plus, scientists usually try and find a mirror in the animal kingdom (fruit flies often) and compare it to a human equivalent.

For example fruit flies breed quickly so you can see whether there is a difference between control populations and test populations if you do something fancy like inhibit a gene or gene sequence. Plus they are kept in standard controlable conditions allowing you to keep environmental influences to a minimum.

Dfens

DaSilva wrote: »

Ok, so that's an extremely exaggerated example, but what do good genetics grant? A greater capacity to improve? I'm just finding it hard to gauge genetics impact in certain areas such as sport or intelligence.

I saw an interesting programme last weekend on Varya Akulova 'Strongest girl in the world'.
In the programme they did an ultrasound of her muscles & found that they were constructed a bit differently than most peoples, to allow more fibres to be packed into the muscle. Some researchers had found that a lot of exceptionally strong people had a particular gene for muscle different to the population at large but I don't think the girl's parents would allow her be tested for it.
I guess in this case, the genetic element would give you a better advantage over some others but it would also need to be coupled with a lot of environmental and personal factors also (diet, training, determination etc.).