AQA Biology Genetic Diversity- Unit 2

It is just my notes from the textbook, but it is A LOT shorter.
It is from the Nelson Thorne book.
Hope it helps :)

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  • Created on: 04-05-12 10:20
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Chapter 9 Genetic Diversity
9.1 Genetic Diversity
Similarities and differences in DNA result in genetic diversity. Organisms are varied, 1.8 million species have
been identified and but there many more.
Between every member of species there are lots of differences, (humans there are about 6.5 billion in 2008
yet we are all different to be seen by one another).
Genetic Diversity
Proteins make organisms different and the DNA determines which protein that will be made for us. So the
similarities and differences between organisms can be described as variation in DNA, therefore it is DNA
which creates genetic diversity.
DNA which codes for one or more polypeptides is called a gene. EG, humans have a gene for blood group
and snapdragons have a gene for petal colour. We all have two alleles, but it depends on which one is used,
so organisms differ in their alleles but not their genes. It is the combination of the alleles that's makes them
different to each other.
The greater the number of alleles that they have the greater chance of genetic diversity. The greater genetic
diversity the more likely the species is able to adapt to environmental changes, as there will be a wider
range of alleles (characteristics). So a greater probability of an organism of getting the characteristics they
need for the certain environment. So the genetic diversity is reduced if they do not have as many alleles.
Selective Breeding
Also known as artificial Selection, it involves identifying the desire characteristics and using them for the
next generation. So the offspring who do not have the characteristics are killed or prevented from breeding.
So unwanted alleles are breed out of the population. The variety of alleles is restricted to being small. So
over many generations this leads to population which has all the desired characteristics but not a lot of
genetic diversity.
It is used mainly for high yielding breeds and domestic animals. EG, plants like wheat are selected so they
have large grains and short stems to reduce disease.
The Founder Effect
When a few individuals found a new region and colonise it. These individuals will only carry some number of
alleles compared to the whole population. These will then develop and the new population will have less
genetic diversity than the population that they come from.
The founder effect is like when a volcano made the whole island (Hawaii) a population moved there and
colonised it, then they are genetically distinct to each other. Over time these will develop in to new species
as they have fewer alleles they will be less able to adapt to new environments.
Genetic Bottlenecks
The population may see a sudden drop in numbers, which may be due to man or nature. The survivors will
have a much smaller variety of alleles, and there genetic diversity will be less. As the population will breed
there alleles will become restricted.
An example would be the elephant seals, by the 1900 there were only 20 left in Mexico. There population
had increased but compared to the California seals they had less genetic diversity and them fewer alleles
making them less likely to be able to adapt to environmental changes.
Application and How science works

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Chapter 9 Genetic Diversity
Ethics of selective breeding in domesticated animals
All scientific behaviours are done by benefits and risked,
Scientific research needs funding, who funds it and how my it differ from farming, producer, supermarket or
animal welfare fund the group.
Ethical implications
Selective breeding has produced livestock and greater yields but it can raise some ethical issues.…read more


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