Okay, we are getting on the same page. Yes, you always have to include the normal gene as an allele, when it is present. The biggest problem now is that it is possible to have more than one mutant gene in a list of alleles. For example, mojave x lesser platinum can produce blue-eyed lucies. One possible explanation for this is that the mojave mutant gene and the lesser mutant gene have the same location in the genome and are alleles. There are three alleles in the list of alleles, but any given ball python has only two. So different ball pythons could have two normal alleles (homozygous), two lesser platinum alleles (homozygous), two mojave alleles (homozygous), a normal allele and a lesser platinum allele (heterozygous), a normal allele and a mojave allele (heterozygous), or a lesser platinum allele and a mojave allele (heterozygous).



> If both(mutant)alleles of a gene are present,then the animal is homozygous for the gene.



This definition of homozygous leaves out the pair of normal genes. And the lesser platinum//mojave gene pair could be included under "both (mutant) alleles".



So I like a definition like this: an animal is homozygous if it has two copies of the same allele at a locus.



>If only one(mutant)allele is present(and one normal allele),then the animal is heterozygous for the gene.



This is true as far as it goes, but it leaves out the the lesser platinum//mojave gene pair.



So I like a definition like this: an animal is heterozygous if it has two different alleles at a locus.



The main trouble with these definitions is that "allele" and "locus" need to be defined. It can be tricky getting over exactly what we mean.



Paul Hollander

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