Download 3. The Gene Pool - NCEA Level 2 Biology

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.