This article delves into the complexities of genetic inheritance, highlighting co-dominance where both alleles are expressed, as seen in the ABO blood group system. It discusses the role of multiple alleles in genetic variation, the impact of epistasis on phenotypes, and how genetic recombination contributes to diversity, providing a comprehensive insight into the mechanisms that drive heredity and evolution.
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Co-dominance is a pattern of genetic inheritance where two alleles for a gene are both fully expressed in the phenotype of heterozygous individuals
Unlike incomplete dominance, where the phenotype is intermediate between the two parents, co-dominance results in offspring that simultaneously display both parental traits without blending
Examples of co-dominance include the human ABO blood group system and certain breeds of cattle
Multiple alleles exist when more than two allelic forms of a gene are present within a population
Multiple alleles allow for a variety of possible genotypes and phenotypes, contributing to genetic diversity and the adaptability and survival of species
The human ABO blood group system is governed by three alleles, Iᴬ, Iᴮ, and i, which result in different blood types
Epistasis is a genetic phenomenon where the expression of one gene is altered by one or more other genes
Epistasis can modify expected phenotypic ratios derived from Mendelian inheritance, leading to deviations such as 9:3:3:1
In Labrador retrievers, coat color is determined by two genes, one of which can suppress pigment expression, resulting in a yellow coat
Recombination is the process of creating offspring with new combinations of alleles, contributing to genetic diversity within a population
Recombination ensures that each individual is genetically unique, providing a mechanism for populations to adapt to changing environments
Recombination occurs during gamete formation through processes such as crossing over during meiosis, where homologous chromosomes exchange segments of DNA
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Co-dominance vs. Incomplete dominance phenotype
Co-dominance: both alleles fully expressed; Incomplete dominance: blended phenotype.
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Example of co-dominance in humans
AB blood type: both Iᴬ and Iᴮ alleles expressed without blending.
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Co-dominance in cattle coat color
Roan cattle: red and white hair colors both fully visible, not blended.
