Human Biology (Year 12)
What is a gene pool?
It is important to note that a population is a group of organisms of the same species living together in a particular place at a particular time.
When studying populations, geneticists consider the characteristics of the population as a whole, as opposed to all of the separate individuals that make up the population. It is more convenient to pool the genotypes of all the individuals capable of reproducing and refer to this as the gene pool.
The gene pool is the sum of all alleles in a given population.
Geneticists are particularly interested in how often each allele of a gene occurs in the gene pool for that population, called allele frequencies.
What are mutations?
Offspring may show variations that do not resemble either parent, and have never occurred before in the history of the family. Therefore, they are due not to an allele being passed down from the parents, but to a new allele being formed – this can happen when the DNA is changed by a mutation, resulting in a different variation of the trait.
An organism with a characteristic resulting for a mutation is called a mutant. The two main types of mutations are gene mutations, which are changes in a single gene so that the traits normally produced by that gene are changed or destroyed, and chromosomal mutations, in which all or part of a chromosome is affected.
If a mistake occurs spontaneously when the DNA molecule is copied during mitosis or meiosis, or when the chromosomes are separated during meiosis, the change may have significant effects on the functioning of the cell.
Many mutations are however repaired, and therefore don’t cause a problem – if they do remain, when the cell divides, the mutated DNA will be copied and passed on to daughter cells. If the daughter cells are gametes, the mutation may be passed on from generation to generation
There are relatively few mutations in human populations relative to the millions of cell divisions that occur, and those that do occur sometimes result in traits better suited to a particular environment, and so may contribute to human survival.
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