Question

It's just a little hard for me to understand the ((Random Drift)) in genetic :(
the book really confused me with difficult explain!

Answer 1

we are in the genetic mechanics of poopulations. there are two ways to change genes when it comes to populations:

the first one is evolution. you got good genes -> you can reproduce more. the daughter generation will be greatly influenced by your genes.

the second one is genetic drift. as you said yourself, this is RANDOM. genes that are passed on to the next generation may be incomplete representation of the gene pool they come from (say, in generation F0, 50% carry the good gene, heterozygous. but statistics make possible, that this good gene may only be passed on to 25% of F1 generation, without evolution influencing this). the gene pool will be changed, at random.

as you acn imagine, genetic drift is stronger if the population is smaller. probability has greater influence on smaller numbers (say, 10 individuals mate -> its easy to pass on "weak" genes, and then comes interbreeding...). NOTE: good genes are not by definition dominant!

further questions? hope I didn't confuse you :-) both mechanisms are always active. in great populations, you won't observe genetic drift because it's compensated by the large number of individuals. but in founder populations, you will strongly observe it. theory is, that the human population was once 50-60 individuals that underwent massive genetic drift.

Answer 2

Just adding another definition from a previous question :) if your still confused..

The wiki definition is "Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling."

So basically the genetics of a population change (not just through natural selection - this isn't through natural selection) through random events. Some animals will die and not be able to reproduce, not as a result of fitness but just through random events (eg. rockfalls, being stepped on). That organism will then not be able to reproduce and the alleles it holds will be lost.

If you have a population with a small number of offspring the effects of random evens will be more dramatic. Say you have a population where the probability of an allele of occurring is 50% (so you have two alleles each of equal change of occuring). Then one unlucky animal becomes victim to a meteor falling out of the sky (okay i'm using silly examples here). Say there were only four animals in this generation (so 2 with allele A and 2 with allele a). The organism that died had the a allele so now in the next generation the probability of receiving an a allele is reduced. Slowly as the probability is reduced initially the allele cannot be returned or is "killed out".

Anyway, take a look at these sites as they give good descriptions: http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation45.html http://www.biology.arizona.edu/evolution/act/drift/about.html

Answer 3

thank U :) so0o0o0 muchchchchchchch

Answer 4

lol, not a problem (I cheated, I wrote that answer up for someone else ages ago :P)