What is genetic dominance?
Genetic dominance refers to the phenomenon where one version of a gene (allele) is expressed and masks the effect of another allele in the same gene pair. The allele that is expressed is known as the dominant allele, while the allele whose effects are masked is called the recessive allele. This concept is a fundamental principle of Mendelian genetics.
To understand genetic dominance, you need to have knowledge of the basic structure of DNA and how genes determine traits. Genes are segments of DNA that contain instructions for building and maintaining an organism. Each gene exists in different versions called alleles. For a specific gene, an individual inherits one allele from each parent, resulting in a gene pair.
The expression of alleles is influenced by their dominance relationships. There are three possible scenarios:
1. Complete dominance: In this case, one allele completely masks the expression of the other allele in the gene pair. For example, if a person carries one dominant allele and one recessive allele for eye color, only the dominant allele's trait (e.g., brown eyes) will be expressed, while the recessive allele's trait (e.g., blue eyes) remains hidden.
2. Incomplete dominance: This occurs when neither allele is completely dominant over the other, resulting in a blending of traits. For instance, if a person inherits one allele for red flowers and one allele for white flowers, the resulting phenotype may be pink flowers due to a mixture of both traits.
3. Co-dominance: In this situation, both alleles are expressed equally without any blending of traits. An example of co-dominance is seen in human blood type inheritance, where the A and B alleles are both expressed in individuals with AB blood type.
To determine the dominance relationship between alleles, one can conduct genetic crosses, like Punnett squares, and observe the inheritance patterns in offspring. These experiments provide insights into the behavior of genes and their dominance relationships.
It's important to note that dominance relationships can vary depending on the specific gene and organism under consideration.
Genetic dominance refers to the relationship between two alleles of a gene, where one allele is expressed over the other in the phenotype of an organism. In simpler terms, it determines which version of a gene, called an allele, is visible or has an effect on an organism.
There are three types of genetic dominance:
1. Complete Dominance: In complete dominance, one allele is dominant over the other, and it fully masks the expression of the recessive allele. The presence of the dominant allele alone determines the phenotype of the organism. In this case, the heterozygous individual (having two different alleles for a particular gene) will exhibit the same phenotype as the homozygous dominant individual (having two copies of the dominant allele).
2. Incomplete Dominance: In incomplete dominance, neither allele is completely dominant over the other. Instead, a blend or intermediate phenotype is observed in the heterozygous individual. For example, if one parent has red flowers and the other has white, the resulting offspring may have pink flowers.
3. Co-Dominance: In co-dominance, both alleles are expressed simultaneously in the heterozygous individual. This means that both traits associated with the alleles are visible in some way. For example, in humans, the ABO blood group system reflects co-dominance; individuals with both A and B alleles will have AB blood type.
Understanding genetic dominance is important in analyzing and predicting inheritance patterns and the expression of traits in offspring.