Genetic Variation and Probability – Definition and Types

Introduction: 

The transmission of characters from parents to offsprings is called heredity, while variation refers to the difference between different individuals. The offspring of the same parent may resemble each other especially, but they may vary in size, color and several other characters  

Genetic Variation and Probability 

Genetic variation is the term used to describe the variation in the DNA sequence in each of our genomes. 

It is the difference between individuals of the same species and the offspring of the same parents.  

Genetic variation makes all the species unique in terms of hair color, skin color or even the shape of our faces. 

Phenotypic variation is the difference in features between individuals of the same species. 

The differences are caused by differences in genes, which is genetic variation. 

Phenotypic variation can be divided into two types depending on how you are able to group the measurements 

• Phenotypic variation can be caused in two main ways: 
• Genetic – controlled entirely by genes. 
• Environmental – caused entirely by the environment in which the organism lives. 

Continuous variation is influenced by genes, and the environment results in a range of phenotypes. Examples include height, mass, finger length etc.., where there can be many ‘in-between’ groups. 

Discontinuous variation results in a small number of phenotypes with no intermediates. 

Discontinuous variations are caused by genes alone.  

For example, people are either blood group A, B, AB or O; are either male or female; can either roll their tongue or not – there are no ‘in-between.’ 

When graphs of these data are plotted, continuous variation gives smooth bell curves (a result of all the small degrees of difference), whereas discontinuous gives a ‘step–like’ shape. 

Genetic variation 

• Examples of genetic variation in humans include: 
• Blood group 
• Eye color 
• Gender 
• Ability to roll tongue 
• Whether ear lobes are free or fixed 

Whether earlobes are attached (lobeless) or free (lobed) is an example of genetic variation. 

Summary

• Variation is the difference between individuals of the same species.
• Genetic variation is the differences in the genotypes of individuals; phenotypic
  variation is the differences in external and internal appearance.
• Continuous variation is influenced by genes and the environment resulting in a range of
  phenotypes, eg, height in humans.
• Discontinuous variation results in a small number of phenotypes with no
  intermediates.
• Discontinuous variation is caused by genes alone, e.g, human blood groups.