alleles
The term used to describe an individual who carries two different alleles of a gene with respect to that gene is called heterozygous.
Horizontal Gene Transfer is probably the term you are looking for
Alternate forms of the same gene are called alleles.
phenotype
The term allele is often used interchangeably with the word gene. Allele/gene is used for the variations seen at each gene locus for a trait on the homologous chromosome pair. For example: If there are three alleles for a trait only two of the alleles will be represented in the genotype of any one individual. The alleles for basic blood types A, B and O are examples. In general the term allele is not used interchangeably with gene in conjunction with the terms locus or loci..therefore Gene locus or gene loci but not allele locus or allele loci.
The term used to describe organisms that consistently pass the same form of a trait to their offspring is "homozygous." Homozygous organisms have two identical alleles for a particular gene, meaning they express the same trait consistently. This contrasts with "heterozygous" organisms, which have two different alleles for a gene and may express a mix of traits.
Carrier
Allele is word used by Mendel for counter parts of an elementon later called factor and renamed as gene e.g. T and t are alleles for a gene that controls height in pea plant .Nasty allele is not biological term .Note word elementon is technical term used by Mendel , it is not element used in Chemistry .
The dominant allele.
alleles
A Gene Probe is a term used to label several techniques used to identify a Gene Loci. a gene probe is often a piece of genetic material, that mirrors the target gene, and is also 'tagged' with dye so it can be identified.
An indiviual letter in a punnett square representing a gene is called an allele. The two genes ( one from each parent ) together is a genotype. There isn't really two forms of a gene.