Final answer:
Alternate forms of genes resulting from mutations are called alleles, which can affect the expression of traits or phenotypes, including lethal phenotypes in cases of recessive and dominant lethal alleles.
Step-by-step explanation:
Alternate forms of genes resulting from mutations are called alleles. An allele is an alternative form of a gene that arises by mutation and is found at the same place on a chromosome. This diversity among alleles can have direct impacts on the expression of a genetic trait or phenotype. For example, in cases of recessive lethal inheritance, an individual must inherit two nonfunctional alleles for an essential gene to express a lethal phenotype, while carriers with just one such allele and one wild-type allele are typically normal.
In contrast, dominant lethal alleles are lethal in both the homozygous and heterozygous forms, but they may not be expressed until adulthood. This can lead to the transmission of such alleles to subsequent generations before the lethal phenotype is manifested, as seen in diseases like Huntington's disease. Hence, alleles are a key component in the inheritance of genetic traits, including those that may be lethal.