1. Complex Patterns of Heredity
Advanced Biology
DNHS

2. Complex Inheritance Patterns
Sometimes the laws and principles of genetics established by Gregor Mendel do not always explain the inheritance patterns seen in an organism.

3. Incomplete Dominance
The heterozygous or hybrid individual will show an intermediate phenotype between the two homozygous individuals
Example – Snap Dragons flower color red crossed with white = pink

4. R = red R’ = white R R R R’ RR’ RR R’ RR’ R RR’ R’ RR’ R’R’ RR’ RR’ R’
Genotype:
All RR’ hybrid
Genotype:
¼ RR; ½ RR’; ¼ R’R’
Phenotype:
All pink
Phenotype:
¼ red; ½ pink; ¼ white

6. Codominance
The heterozygous individual will show the phenotypes of each of the homozygous individuals
Example – chickens, black+white=checkered (black and white)

7. Multiple Alleles
Situation wherein there exists more than two alleles for a specific trait.
Example – Blood type in humans (A, B, O alleles)

8. Sex Linked Traits
When a trait is seen in one sex more often than another due to a gene that is carried on one of the sex chromosomes
Examples – eye color in fruit flies and hemophilia and color blindness in humans

11. Polygenic Inheritance
When a trait is influenced by many genes
Tends to be a wide range of phenotypic variation
Examples: skin color, hair color, height in humans

12. Test Crosses
A situation in which there is an individual of unknown genotype
To determine the genotype you would cross it with a pure recessive individual

13. Pedigree
A graphic genetic family tree that follows a trait through several generations

15. Aneuploidy A condition of having an abnormal chromosome number
Example – Down’s Syndrome, Sex Chromosome Aneuploidies (Turner Syndrome)