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A monohybrid cross is a cross between two organisms with different variations at one genetic locus of interest. [ 1 ] [ 2 ] The character(s) being studied in a monohybrid cross are governed by two or multiple variations for a single location of a gene.
The forked-line method (also known as the tree method and the branching system) can also solve dihybrid and multi-hybrid crosses. A problem is converted to a series of monohybrid crosses, and the results are combined in a tree. However, a tree produces the same result as a Punnett square in less time and with more clarity.
Mendel found support for this law in his dihybrid cross experiments. In his monohybrid crosses, an idealized 3:1 ratio between dominant and recessive phenotypes resulted. In dihybrid crosses, however, he found a 9:3:3:1 ratios. This shows that each of the two alleles is inherited independently from the other, with a 3:1 phenotypic ratio for each.
The first uses of test crosses were in Gregor Mendel’s experiments in plant hybridization.While studying the inheritance of dominant and recessive traits in pea plants, he explains that the “signification” (now termed zygosity) of an individual for a dominant trait is determined by the expression patterns of the following generation.
Mendelian inheritance; Merodiploid; Microfluidic whole genome haplotyping; Midphalangeal hair; Minor allele frequency; Monocentric chromosome; Monohybrid cross; Muller's morphs; Multilocus genotype; Mutant
This cross results in the expected phenotypic ratio of 9:3:3:1. Another example is listed in the table below and illustrates the process of a dihybrid cross between pea plants with multiple traits and their phenotypic ratio patterns. Dihybrid crosses are easily visualized using a 4 x 4 Punnett square.
In this case, the filial generation formed after the back cross may have a phenotype ratio of 1:1 if the cross is made with recessive parent or else all offspring may be having phenotype of dominant trait if the backcross is with a parent having the dominant trait. The former of these traits is also called a test cross.
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart.