Table of contents
- Meiosis - The Genetics of …
- Independent Assortment and Crossing Over
- Crossing Over and Genetic Diversity
- Dominance and Crossing Over
- Mendel's Law & Mendelian Genetics
- Chromosomes X and Y and …
- Chromosome Mutations
- Genetic Mutations
- Mutation Frequency and Polyploidy
- Theory of Natural Selection
- Darwin's Finches & Natural Selection
- Selective Breeding
- Genetic Engineering Advantages & Disadvantages
- The Gene Pool and Speciation
- Adaptive Radiation
Mutation Frequency and Polyploidy
- Genetics and Evolution
The previous two pages have investigated mutations, and this page continues with more information related to genetic mutations.
Humans are diploid creatures, meaning for every chromosome in our body, there is another one to match it. Read the following
- Haploid creatures have one of each chromosome
- Diploid creatures have two of each chromosome
- Triploid creatures have three of each chromosome
- Polyploid creatures have three or more of each chromosome
- They can be represented by n where n equals haploid, 2n equals diploid and so on.
It is possible for a species, particularly plant species, to produce offspring that contains more chromosomes than its parent. This can be a result of non-disjunction, where normally a diploid parent would produce diploid offspring, but in the case of non-disjunction in one of the parents, produces a polyploid.
In the case of triploids, although the creation of particular triploids in species is possible, they cannot reproduce themselves because of the inability to pair homologous chromosomes at meiosis, therefore preventing the formation of gametes.
Polyploidy is responsible for the creation of thousands of species in today's planet, and will continue to do so. It is also responsible for increasing genetic diversity and producing species showing an increase in size, vigour and an increased resistance to disease.
This page and the previous two have investigated the different ways that mutations arise, and the following elaborates on the ways in which mutations are instigated.
Barring all external factors, mutations occur very rarely, and are rarely expressed because many forms of mutation are expressed by a recessive allele.
However there are many mutagenic agents that artificially increase the rate of mutations in an organism. The following are some factors that increase genetic mutations in organisms
- Members of species in a particular geographic area or ethnic origin are more susceptible to mutations
- High dosages of X-Rays or ultraviolet light can increase the likeliness of a mutation
- Radioactive substances increase the rate of mutations exponentially
As mentioned previously, genetic mutations are a source of new variation in a species because it physically alters the sequence of nucleotides in a given sequence, therefore altering the genome in a unique way.
The next pages investigate genetic diversity in more detail, an how certain alleles (perhaps mutations) are favoured over other alleles in natural selection...
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