Final answer:
The segregation of unit factors or alleles during gamete formation happens during the first division of meiosis, where each gamete receives one allele from each gene pair, allowing for various combinations of genetic traits in the offspring.
Step-by-step explanation:
During gamete formation, the segregation of unit factors, or alleles, for each gene, occurs in a process known as meiosis. The law of segregation describes how these paired unit factors separate into different gametes. Specifically, this segregation happens during the first division of meiosis, wherein homologous chromosomes, carrying different alleles of a gene, are distributed into separate daughter nuclei.
Each gamete then receives only one homolog from each pair, ensuring that offspring have an equal chance of inheriting any combination of factors from their parents. The formation of gametes can be compared to tossing a coin, whereby the probability of a gamete carrying one allele is as likely as it carrying the alternative allele. For example, in the case of a heterozygous plant genotype Bb, there is a 50 percent chance for a gamete to contain allele B and a 50 percent chance for allele b.
It is also important to note that linkage may affect the segregation pattern, as alleles close to each other on the same chromosome tend to be inherited together. However, in the case of independent assortment, where genes are located on different chromosomes or far enough apart on the same chromosome, every possible combination of alleles is equally likely to occur in gametes. This phenomenon leads to genetic variation in the resulting offspring when fertilization combines alleles from different parents.