Final answer:
Mendel's first law, known as the law of segregation, does not state that each gene determines the expression of multiple traits. Instead, it covers the segregation of alleles during gamete formation and the inheritance of one allele per gene from each parent. The incorrect option also conflicts with Mendel's second law, the law of independent assortment, which pertains to gene assortment in gametes.
Step-by-step explanation:
Mendel's first law is described by all of the following EXCEPT c) Each gene determines the expression of multiple traits. Mendel's first law, also known as the law of segregation, includes the key concepts that alleles of a gene separate or segregate during gamete formation, and offspring inherit one allele for each gene from each parent. The principle that genes sort independently is actually Mendel's second law, known as the law of independent assortment. Mendel observed that each trait is controlled by a pair of alleles and these alleles segregate during the formation of gametes so that each gamete carries only one allele for each trait.
The law of segregation supports the 3:1 phenotype ratio observed in the F2 generation of his monohybrid crosses and the equal segregation of alleles is why the Punnett square can accurately predict the offspring of parents with known genotypes. This law establishes that it is the pair of alleles from each parent that segregate during meiosis, ensuring gametes carry only one allele for each gene, which reassorts during fertilization, thus restoring the diploid state.
On the contrary, it is incorrect to associate Mendel's first law with the concept that each gene determines the expression of multiple traits; this falls under the scope of genes showing pleiotropy or polygenic inheritance, which are not covered by Mendel's laws of inheritance. Independent assortment provides for a great degree of diversity in offspring, but does not pertain to a gene's influence on multiple traits.