There isn't one single perfect synonym for "genes," as the word has a specific scientific meaning. However, depending on the context, you could use some of these alternatives:

General terms:

* Hereditary factors: This emphasizes the role of genes in passing traits from parents to offspring.

* Genetic material: This refers to the DNA that carries the genetic information.

* Genetic code: This refers to the specific sequence of nucleotides in DNA that determines the traits.

More specific terms:

* Alleles: These are alternative forms of a gene.

* Loci: These are the specific locations on chromosomes where genes are found.

* Genotype: This refers to the genetic makeup of an organism.

* Genome: This refers to the complete set of genes in an organism.

The best alternative depends on the specific context and what you want to emphasize.