Complex Patterns of Heredity

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)