What exactly are multiple alleles?

I assume that you already know what are normal alleles .

Now the answer is as under ....

In pea plant the height is decided by two alleles T and t .

Thus they are 'partners' of each other and together decide a single character the height of the plant .

TT = pure tall ; Tt = hybrid tall and only tt= dwarf.

This is how normal alleles ( Only two in number ) function.

But in MULTIPLE ALLELES THE PARTNERS THAT DECIDE A SINGLE CHARACTER ARE ALWAYS MORE THAN TWO IN NUMBER .

Example # 1 == In human blood there are three types of blood groups ( Not counting Rh + and Rh - ) . And they are decided by THREE alleles . A,B and O.

AA= blood group is A ; BB = blood group is B ; AB = the blood group is AB as both are co-dominant

AO = Blood group is A as O is recessive to A.

BO = Blood group is B as O is recessive to B.

OO = Blood group is O as no dominant gene is present O can express it self !!!

Example # 2 = Human eye color is expressed in different colors such as black , brown , green and blue . Thus it is an example of multiple alleles .

Example #3 = Human hair color= Black , brown , blond and red head are examples of multiple alleles .

Finally MULTIPLE ALLELES ARE NOT TO BE CONFUSED OR EQUATED WITH MULTIPLE GENE FACTOR .

IT IS A DIFFERENT THING ALTOGETHER.

It's when you have several copies of the gene (not necessarily just two). A diploid organism will have two alleles (they may be dominant/recessive, or incompletely dominant, or even identical). However, the gene itself may have more than two alleles in the population.

For example, a gene 'A' that has three alleles may be designated a1, a2 and a3. A random individual may have any two of these.

Tetraploid organisms that have identical genomes will have four alleles in one individual, and so on. If the genomes are not identical (for example, wheat), each pair is usually considered a seperate gene.

There are two types of allele, dominant (F) and recessive (f). Dominant is the 'leader' and takes control if it is present, even if a recessive allele is also present, but to have the features of a recessive allele affect you, you have to have two recessive alleles and no dominant allele.

Alleles are just different versions of the same gene. Like the Pokemon games, you have a red version and a blue version.

addition to above answer

THREE OR MORE ALTERNATIVE GENES REPRESENTING THE SAME LOCUS IN A GIVEN PAIR OF CHROMOSOMES.