Genetic Variation
Genetic variation refers to the variation in the genome sequences between individual organisms of a species. Individual differences or population differences can both be referred to as genetic variations. It is primarily caused by mutation, but other factors such as genetic drift and sexual reproduction also play a major role.
Quantitative Genetics
Quantitative genetics is the part of genetics that deals with the continuous trait, where the expression of various genes influences the phenotypes. Thus genes are expressed together to produce a trait with continuous variability. This is unlike the classical traits or qualitative traits, where each trait is controlled by the expression of a single or very few genes to produce a discontinuous variation.
An investigation of shrew tail length showed that the length of tails varied from 24mm to 66mm. In one generation recorded out of a population of 2,360 shrews only 2 were as long as 66mm. In another cross a new true-breeding shrew variety was used which gave a range of F1 tail lengths with a variance of 0.316. In the crosses using the original variety there was an even greater range of tail lengths and a variance of 0.725.
Will further artificial selection be a useful way to change shrew tail length?
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