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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 phenotype that may appear in the presence of a given genotype can in some instances be influenced by many other factors, as when polygenic ...
The word pedigree is a corruption of the Anglo-Norman French pé de grue or "crane's foot", either because the typical lines and split lines (each split leading to different offspring of the one parent line) resemble the thin leg and foot of a crane [3] or because such a mark was used to denote succession in pedigree charts.
This is an accepted version of this page This is the latest accepted revision, reviewed on 27 February 2025. Science of genes, heredity, and variation in living organisms This article is about the general scientific term. For the scientific journal, see Genetics (journal). For a more accessible and less technical introduction to this topic, see Introduction to genetics. For the Meghan Trainor ...
For example, if p=0.7, then q must be 0.3. In other words, if the allele frequency of A equals 70%, the remaining 30% of the alleles must be a, because together they equal 100%. [5] For a gene that exists in two alleles, the Hardy–Weinberg equation states that (p 2) + (2pq) + (q 2) = 1. If we apply this equation to our flower color gene, then
Punnett square: If the other parent does not have the recessive genetic disposition, it does not appear in the phenotype of the children, but on the average 50% of them become carriers. A hereditary carrier ( genetic carrier or just carrier ), is a person or other organism that has inherited a recessive allele for a genetic trait or mutation ...
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.
Each has one allele for purple and one allele for white. In the offspring, in the F 2-plants in the Punnett-square, three combinations are possible. The genotypic ratio is 1 BB : 2 Bb : 1 bb. But the phenotypic ratio of plants with purple blossoms to those with white blossoms is 3 : 1 due to the dominance of the allele for purple.
Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal color in pea plants. The letters B and b represent genes for color, and the pictures show the resultant phenotypes. This shows how multiple genotypes (BB and Bb) may yield the same phenotype (purple petals).