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3. THE GENE POOL UNDERSTAND THE CONCEPT OF A GENE POOL THE GENE POOL KEYWORDS • Population: A group of interbreeding individuals of one species in a certain area. • Gene Pool: All the genes, including all the different alleles for each gene, that are present in a population at any one time. • Locus: The location of a gene or specific gene sequence on a chromosome. EXAMPLE OF A GENE POOL EXPRESSING ALLELE FREQUENCY • We can quantify gene pools by calculating the frequency of an allele: • Eg: population of 20 individuals = 40 alleles at a particular locus. • 8 homozygous dominant, 6 homozygous recessive, 6 heterozygous • How many of each individual allele exist? • B = 8 x 2 + 6 =22 b = 6 x 2 +6 = 18 • f(B) = 22/40 = 0.55 f(b)= 18/40 = 0.45 A LARGE GENE POOL (RANGE OF ALLELES) • Is a good thing as it provides a source of variation for any changes that may occur in the environment. • It is also big enough to resist changes from death, random events and disease. • Populations which can interbreed with neighbouring populations are more likely to survive changes as their total gene pool is the sum of the two populations. PUREBREEDING REDUCES THE GENE POOL • Purebreds or purebreeds, are cultivated varieties of an animal species, achieved through the process of selective breeding. If the lineage of a purebred animal is recorded, then that animal is said to be pedigreed. Because pure-breeding creates a limited gene pool, purebred animal breeds are also susceptible to a wide range of congenital health problems. • Breeding from too small a gene pool, especially direct inbreeding, can lead to the passing on of undesirable characteristics or even a collapse of a breed population due to inbreeding depression.