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Complex Patterns of Heredity

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Presentation on theme: "Complex Patterns of Heredity"— Presentation transcript:

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)


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