Mendel's Law of segregation states that each organism has two factors for each trait in their DNA. During gamete formation, these two factors separate, with each gamete receiving one factor. At fertilization, the factors combine with their partners once again; the offspring receiving one factor from each parent
Mendel's Law of independent assortment states that members of one factor segregate from another factor for a different trait on a different chromosome independently.
Genes which are not linked illustrate Mendel's law of independent assortment. Because the alleles for the genes are on different chromosomes, during gamete formation the genes have no effect on one another. A pea gamete having the allele for smooth seeds has no effect on whether the gamete has the allele for yellow or green seeds. When doing a punet square, the alleles of two or more traits that are not on the same can be treated as two or more
When considering genes which are linked (on the same chromosome), only Mendel's law of segregation applies. During gamete formation, the chromosomes separate and each sex cell gets one version of each chromosome pair. When two alleles for two respective traits are present on this chromosome, these traits are said to be linked; in that a gamete with the chromosome will always contain both traits (baring mutations). A gamete with the one of these alleles will always possess the other linked allele as well (baring mutations).
Crossing over can be discussed through Mendel's law of segregation. Crossing over occurs when an allele which shares a chromosome with a linked allele, breaks off and changes places with its partner on another chromosome. This mutation allows for variation in the phenotypic expression of linked alleles. It relates to the law of segregation through the above discussion of linked genes. In that
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