Dissimilarity
In contrast to a gamete, the diploid somatic cells of an individual contain one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg; that is, the cells of the offspring have genes expressing characteristics of both the father and the mother. A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the somatic cells of the individual that produced the gametes. They can be hybrids produced through crossover (a form of genetic recombination) of chromosomes, which takes place in meiosis. This hybridization has a random element, and the chromosomes tend to be a little different in every gamete that an individual produces. Additionally, base pairs in chromosomes often undergo random mutations resulting in modified DNA (and subsequently, new proteins and phenotypes). This mutation, recombination, and the fact that the two chromosome sets ultimately come from either a grandmother or a grandfather on each parental side account for the genetic dissimilarity of siblings.
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