Types of Dominance
Five Misconceptions in Genetics. By Crystal Jeter Product Developer. Students may bring a variety of misconceptions with them when they enter a study of genetics. Watch your classroom for the 5 common misconceptions listed below. If you find any of them, just use the simple explanations—also provided below—to dispel your students’ incorrect notions. One set of alleles is responsible for ...
Autosomal traits are passed on from parents to offspring independent of gender, whereas, because sex-linked traits are carried on the X chromosome and NOT the Y chromosome, males (XY (hemizygous)) have a 50% chance of being either recessesive or dominant for the trait . With sex-linked traits, females however have more possible outcomes in terms of dominant/recessive traits because of their two X chromosomes (XX).
These genes are inherited with the X chromosome (from the mother if it is a boy or from either mother or father if it is a girl). Females have two X chromosomes (XX), while males have one X chromosome and one Y chromosome (XY). This means females have two alleles for X-linked genes while males only have one.
Codominance is a form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive. A typical example showing codominance is the ABO blood group system.
Complete Dominance and Other Types of Dominance The flowers on Mendel's pea plant are an example of complete dominance, or when the dominant allele completely covers up the recessive allele. In addition to complete dominance, scientists have found incomplete dominance, where there is a blending, and codominance, where both alleles show up.
Epistasis is a situation in genetics in which the expression of a particular gene depends on the presence of a modifier gene. It is different from dominance, which is when one allele of a gene is expressed over another allele of the same locus. Epistasis has causes at the genetic and molecular level ...
Incomplete Dominance Vs. Co-Dominance. Incomplete genetic dominance is similar to but different from co-dominance. Whereas incomplete dominance is a blending of traits, in co-dominance an additional phenotype is produced and both alleles are expressed completely. The best example of co-dominance is AB blood type inheritance. Blood type is determined by multiple alleles recognized as A, B, or O and in blood type AB, both phenotypes are fully expressed.
Multiple alleles, incomplete dominance, and codominance In the real world, genes often come in many versions (alleles). Alleles aren't always fully dominant or recessive to one another, but may instead display codominance or incomplete dominance.