independent assortment

Examples of independent assortment in the following topics:

• Mendel's Law of Independent Assortment

  • Independent assortment allows the calculation of genotypic and phenotypic ratios based on the probability of individual gene combinations.
  • Mendel's law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes: every possible combination of alleles for every gene is equally likely to occur.
  • The independent assortment of genes can be illustrated by the dihybrid cross: a cross between two true-breeding parents that express different traits for two characteristics.
  • The law of independent assortment states that a gamete into which an r allele sorted would be equally likely to contain either a Y allele or a y allele.
  • The values along each forked pathway can be multiplied because each gene assorts independently.

• Genetic Linkage and Violation of the Law of Independent Assortment

  • Genes that are on the same chromosome, or "linked", do not assort independently, but can be separated by recombination.
  • Although all of Mendel's pea characteristics behaved according to the law of independent assortment, we now know that some allele combinations are not inherited independently of each other.
  • Genes that are located on separate non-homologous chromosomes will always sort independently .
  • However, because of the process of recombination, or "crossover," it is possible for two genes on the same chromosome to behave independently, or as if they are not linked.
  • Mendel's seminal publication makes no mention of linkage, and many researchers have questioned whether he encountered linkage, but chose not to publish those crosses out of concern that they would invalidate his independent assortment postulate.

• Mendel's Law of Segregation

  • In Mendel's experiments, the segregation and the independent assortment during meiosis in the F1 generation give rise to the F2 phenotypic ratios observed by Mendel.

• Genetic Linkage and Distances

  • Mendel's work suggested that traits are inherited independently of each other.
  • Perfectly unlinked genes correspond to the frequencies predicted by Mendel to assort independently in a dihybrid cross.
  • In (a), two genes are located on different chromosomes so independent assortment occurs during meiosis.

• Meiosis I

  • Random, independent assortment during metaphase I can be demonstrated by considering a cell with a set of two chromosomes (n = 2).

• Genetic Maps

  • The study of genetic maps begins with linkage analysis, a procedure that analyzes the recombination frequency between genes to determine if they are linked or show independent assortment.

• Epistasis

  • Note that we are assuming the interacting genes are not linked; they are still assorting independently into gametes.

• Nonrandom Mating and Environmental Variance

  • One common form of mate choice, called positive assortative mating, is an individual's preference to mate with partners that are phenotypically similar to themselves.
  • The American Robin may practice assortative mating on plumage color, a melanin based trait, and mate with other robins who have the most similar shade of color.

• Defining Population Evolution

  • When recombination occurs during sexual reproduction, genes are usually shuffled so that each parent gives its offspring a random assortment of its genetic variation.
  • However, genes that are close together on the same chromosome are often assorted together.

• Meiosis II

  • The cells produced are genetically unique because of the random assortment of paternal and maternal homologs and because of the recombining of maternal and paternal segments of chromosomes (with their sets of genes) that occurs during crossover .