According to Mendel's first principle of genetics, what can be said about the sex cells of a plant or animal?

Mendel's first principle of genetics, known as the Law of Segregation, posits that during the formation of gametes (sex cells), the two alleles for a trait segregate from each other so that each gamete carries only one allele for each trait. This principle is fundamental to understanding how traits are inherited in offspring.

The correct choice states that sex cells may contain one factor for different traits but not both. This reflects the essence of the Law of Segregation, which emphasizes that an organism's alleles for a trait are separated during meiosis, resulting in gametes that carry a single allele for each trait. Therefore, when fertilization occurs, each parent contributes one allele to form a complete set of alleles in the offspring, enabling the expression of traits based on the combination of alleles inherited from both parents.

In contrast, the other choices do not accurately capture Mendel's principle. For instance, stating that sex cells contain both factors needed to express traits does not align with the Law of Segregation, as each sex cell holds only one allele. Similarly, claiming that sex cells determine dominant traits expressed in offspring oversimplifies the genetic process, as dominance relationships are established based on the alleles that the offspring