Mutations and recombination are major sources of variation. Mutations are the original source of genetic variation. A mutation is a permanent alteration to a DNA sequence. De novo new mutations occur when there is an error during DNA replication that is not corrected by DNA repair enzymes. Mutations may be beneficial to the organism; deleterious harmful to the organism; or neutral have no effect on the fitness of the organism. Somatic mutations can accumulate in our cells and are mostly harmless.
They can lead to local changes in tissues such as moles appearing on the skin, and can also have more serious effects — for example leading to cancer. To learn more about the role of somatic mutations in cancer have a look at this paper by Martincorena and Campbell 1.
Variation is the differences in the characteristics of organisms. It can be caused by the genes an individual inherits or the environment it lives in. Extensive genetic variation is contained within a population of any species and is clearly visible in the domestic dog species, as shown in the photograph below.
Variation within genes leads to different genotypes , which can be seen by the individuals having different phenotypes. For example, the dogs above all have different fur colours and fur lengths. This page has been archived and is no longer updated. A mutation is a change in a genetic sequence. Mutations include changes as small as the substitution of a single DNA building block, or nucleotide base, with another nucleotide base.
Meanwhile, larger mutations can affect many genes on a chromosome. Along with substitutions, mutations can also be caused by insertions, deletions, or duplications of DNA sequences.
Some mutations are hereditary because they are passed down to an offspring from a parent carrying a mutation through the germ line, meaning through an egg or sperm cell carrying the mutation.
0コメント