Phenotype and Genotype

 Your 46 chromosomes are a combination of chromosomes inherited from mum and dad.  Each chromosome is made up of two chromatids, one from mum and one from dad.  Although the genes on each chromatid may code for the same thing, you may have inherited a different variety of the gene from mum as opposed to dad.

 Allele is the name given to the variety of genes that code for the one thing.  Can be compared to the way we see dogs and but there are many varieties of dogs.  When looking back at the ear survey we were in fact investigating the way the alleles work to form the ear appearance.  Because we were only able to investigate the appearance we could only comment on the phenotype of each class member.  However, if we were to do genetic testing combined with the information we gathered from your parents, we would be able to determine your genotype or the combination of alleles you have.

 Alleles can be dominant or recessive.  Which, has nothing to do with how common they or the trait occurs but with the combination of alleles you have.  Dominant alleles are characterised by capital letters, eg. E  And recessive alleles are characterised by initial letters, eg. e  To have a recessive trait you must have two copies of the recessive allele (homozygote ee)  To have the dominant trait you can either have one copy of the dominant allele and one recessive allele (hetrozygote Ee) or two copies of the dominant allele (homozygote EE).

 Although you may have two parents with the dominant trait of free earlobes, there is still the possibility of producing a child with attached earlobes.  However, two parents with the recessive trait of attached earlobes cannot produce a child with free earlobes.

 If the allele combination or genotype of parents is known punnet squares can be used to determine the likely combinations of their offspring.