I) Lethal gene: A lethal gene is a gene whose expression results in the death of the organism, often at an early stage of development.

Here are the definitions for the terms in genetics:

i) Lethal gene: A lethal gene is a gene whose expression results in the death of the organism, often at an early stage of development.

ii) Epistasis: Epistasis is a phenomenon where the expression of one gene (the epistatic gene) masks or modifies the effect of another gene (the hypostatic gene) at a different locus.

iii) Incomplete dominance: Incomplete dominance is a form of inheritance in which one allele is not completely dominant over the other, resulting in a heterozygous phenotype that is an intermediate blend of the two homozygous phenotypes.

iv) Linkage: Linkage refers to the tendency of genes or alleles that are located close together on the same chromosome to be inherited together during meiosis, rather than assorting independently.