Re: what is a group of alleles called?

There are a few possible interpretations of your question.

Are you referring to a group of alleles in a single gene?

A group of alleles in the SAME GENE, especially where each allele is a slightly different mutation with a slightly diffent phenotype, is called an "allelic series". Another way of saying this is that an allelic series consists of all the known alleles within a single gene.

Mutant alleles that do not complement each other (i.e. when you make a heterozygote between two DIFFERENT, MUTANT, non-wild type alleles, the phenotype looks mutant) are called a "complementation group". Alleles in a complementation group are also usually in the same gene. Think of it this way: if you have two mutant alleles in gene A, and you have only two copies of every gene, than you can't possibly have a normal wild type copy of gene A, so you will look mutant.

Or are you referring to a group of alleles in two or more DIFFERENT GENES that are located next to each other on the same chromosome?

In this case, a set of alleles that are linked together on the same parental homolog is known as a "haplotype" or a "haplotype group". Alleles within a haplotype are generally inherited together. For instance if gene A is located next to gene B, and the allele at A is a1 and the allele at B on the same chromosome is b1, the a1 b1 combination will not segregate independantly, but will instead segregate together. This means that in the next generation, progeny that have the a1 allele will be very likely to also carry the b1 allele.

• Here's a glossary of genetics terms
• More information on haplotypes
• On complementation grouping