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Letters and Punnett squares are used to demonstrate the principles of dominance in teaching, and the upper-case letters are used to denote dominant alleles and lower-case letters are used for recessive alleles. An often quoted example of dominance is the inheritance of seed shape in peas.
An individual that is homozygous-dominant for a particular trait carries two copies of the allele that codes for the dominant trait. This allele, often called the "dominant allele", is normally represented by the uppercase form of the letter used for the corresponding recessive trait (such as "P" for the dominant allele producing purple flowers ...
In this example, both parents have the genotype Bb. For the example of eye color, this would mean they both have brown eyes. They can produce gametes that contain either the B or the b allele. (It is conventional in genetics to use capital letters to indicate dominant alleles and lower-case letters to indicate recessive alleles.)
An uppercase letter is typically used to represent the dominant allele, and a lowercase letter is used to represent the recessive allele. The possible genotypes of the offspring can then be determined by combining the parent genotypes. [10] In the example on the right, both parents are heterozygous, with a genotype of Bb.
Then, p 2 is the fraction of the population homozygous for the first allele, 2pq is the fraction of heterozygotes, and q 2 is the fraction homozygous for the alternative allele. If the first allele is dominant to the second then the fraction of the population that will show the dominant phenotype is p 2 + 2pq, and the fraction with the ...
In genetics shorthand, heterozygous genotypes are represented by a pair of non-matching letters or symbols, often an uppercase letter (indicating a dominant allele) and a lowercase letter (indicating a recessive allele), such as "Aa" or "Bb". Contrast homozygous. homoallele A mutant allele having a different mutation at
According to the model of Mendelian inheritance, alleles may be dominant or recessive, one allele is inherited from each parent, and only those who inherit a recessive allele from each parent exhibit the recessive phenotype. Offspring with either one or two copies of the dominant allele will display the dominant phenotype.
In the pea plant example, the capital "B" represents the dominant allele for purple blossom and lowercase "b" represents the recessive allele for white blossom. The pistil plant and the pollen plant are both F 1-hybrids with genotype "B b". Each has one allele for purple and one allele for white.