Incomplete Dominance & Codominance Section 11-3 in Book.
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Transcript of Incomplete Dominance & Codominance Section 11-3 in Book.
Incomplete Dominance & Codominance
Section 11-3 in Book
Review of Mendel’s Principles
Genes are passed parents offspring; get one allele from each parent
During Meiosis, the alleles for a gene segregate from each other.
During Meiosis, genes independently assort with each other.
Exceptions to Mendel’s principles
Sometimes, there is no dominant or recessive gene, or the trait is controlled by many alleles or genes.
Neither allele is dominant Heterozygous phenotype produces 3rd phenotype
somewhere between homozygous phenotype.
Incomplete Dominance
1. Incomplete Dominance
Examples: Trait: Flower Color
Expressions: Red x White Pink
RR= Red; RW= pink; WW= white
straight hair, wavy, curly
Incomplete Dominance
In codominance, both alleles are dominant and are expressed in heterozygous organisms.
Codominance
2. Codominance Both alleles contribute to the phenotype.
Example: In come chickens
Black Chicken x White Speckled Chicken
YOU tell me which type of dominance…
Codominance!
Type of Dominance?
Incomplete Dominance!
Type of Dominance?
Incomplete Dominance!
Multiple Alleles
Gene has more than two alleles. Ex. Blood type in humans
Polygenic Traits
Trait controlled by two or more genes Ex. Skin color of humans (4 different
genes) Reddish-brown eyes of fruit flies
Sex-Linked Genes/Traits
Special pattern of inheritance for genes located on the X and Y chromosomes.
Y chromosome is very small only holds a few genes
3 human genes associated with color vision are on the X chromosome.
In males, a defected version of these genes produces colorblindness.
Why the difference? Males only have one X chromosome.
Pedigree