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The Punnett square is a visual representation of Mendelian inheritance, a fundamental concept in genetics discovered by Gregor Mendel. [10] For multiple traits, using the "forked-line method" is typically much easier than the Punnett square. Phenotypes may be predicted with at least better-than-chance accuracy using a Punnett square, but the ...
A Punnett square for one of Mendel's pea plant experiments – self-fertilization of the F1 generation. The Law of Segregation of genes applies when two individuals, both heterozygous for a certain trait are crossed, for example, hybrids of the F 1-generation.
A quantitative trait locus (QTL) is a region of DNA which is associated with a particular phenotypic trait, which varies in degree and which can be attributed to polygenic effects, i.e., the product of two or more genes, and their environment. [2] These QTLs are often found on different chromosomes. The number of QTLs which explain variation in ...
A polygenic trait is one whose phenotype is dependent on the additive effects of multiple genes. The contributions of each of these genes are typically small and add up to a final phenotype with a large amount of variation. A well studied example of this is the number of sensory bristles on a fly. [25]
Punnett square for three-allele case (left) and four-allele case (right). White areas are homozygotes. Colored areas are heterozygotes. Consider an extra allele frequency, r. The two-allele case is the binomial expansion of (p + q) 2, and thus the three-allele case is the trinomial expansion of (p + q + r) 2.
Traits controlled by two or more genes are said to be polygenic traits. Polygenic means "many genes" are necessary for the organism to develop the trait. For example, at least three genes are involved in making the reddish-brown pigment in the eyes of fruit flies. Polygenic traits often show a wide range of phenotypes.
The predictions of the combinations of the gametes will be constructed on a Punnett square. [citation needed] In conducting a monohybrid cross, Mendel initiated the experiment with a pair of pea plants exhibiting contrasting traits, one being tall and the other dwarf. Through cross-pollination, the resulting offspring plants manifested the tall ...
This Punnett square illustrates incomplete dominance. In this example, the red petal trait associated with the R allele recombines with the white petal trait of the r allele. The plant incompletely expresses the dominant trait (R) causing plants with the Rr genotype to express flowers with less red pigment resulting in pink flowers.