Studying inheritance

Genotype:

• Genotype is the genetic constitution of an organism  
• It describes all the alleles that an organism has
• The genotype determines the limits within which the characteristics of an individual may vary
• For example, it may determine that a human baby could grow to be 1.8m tall, but the actual height that this individual reaches is affected by other factors, such as diet

Phenotype:

• Is the observable or biochemical characteristics of an organism
• It is the result of the interaction between the expression of the genotype and the environment
• The environment can alter an organism's phenotype

Genes:

• A gene is a length of DNA that is a sequence of nucleotide bases, that normally code for a particular polypeptide 
• A gene does this by coding for a particular polypeptide
• This polypeptide may be an enzyme that is needed in the biochemical pathway that leads to the production of the characteristic (for example, a gene could code for a brown pigment in the iris of the eye)
• Genes exist in two, or more different forms called alleles
• The position of a gene on a particular DNA molecule is known as the locus

Alleles:

• One of the different forms of a gene
• For example, in pea plants there is a gene for the colour of the seed pod
• This gene has two…