What does Mendel's first law of segregation state about inheritance?

Mendel's first law of segregation articulates that during the formation of gametes, the two alleles for a trait segregate from each other so that each gamete carries only one allele for each gene. This principle is fundamental to understanding Mendelian genetics and highlights the process of meiosis, where the alleles separate. Hence, each parent indeed contributes one allele to the offspring for any given trait, ensuring that offspring inherit one allele from each parent. This law is crucial for determining the genetic makeup of an organism and predicting the inheritance patterns of traits in future generations.

In contrast, the other options do not accurately encapsulate the essence of Mendel's findings. While independent assortment is a separate principle relevant to the inheritance of multiple traits, it is not what the first law addresses specifically. The concepts regarding the expression of dominant versus recessive alleles are related to phenotype expression and do not describe the segregation process that occurs during gamete formation.