Genetics 201

Multiple Alleles: Blood Type Phenotypes

Multiple Alleles Type A: IAIA or IAi Type B: IBIB or IBi Type AB: IAIB Type O: ii

16-1 Genes and Variation Single-gene and polygenic traits Widows peak is a single gene trait – a single gene with two alleles Polygenic Traits are controlled by two or more genes This means that a polygenic trait can have many possible genotypes ant thus phenotypes.

Polygenic Traits (Continuous Variation)

Polygenic Traits (Continuous Variation)

Polygenic Traits (Continuous Variation)

Thomas Hunt Morgan (1866-1945)

Drosophila Eye Color ( WT vs. White)

Fruit Fly Sex-linked Eye Color Inheritance

Colorblindness

Pedigree Symbols

Albinism a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. AA and Aa are normally pigmented. aa has albino phenotype.

Hemophilia: The Royal Disease

Recombination and Linked Genes Recombination also known as “crossing over”

Recombination and Linked Genes Result: Certain traits tend to be inherited together more often. Also, mixes up genes more creating more variation from sexual reproduction.

Patterns of Inheritance: Sickle-cell Anemia and Malaria Incidence of Sickle-cell Anemia in Africa Incidence of Malaria in Africa

How does Sickle-cell combat malaria? Sickle-cell trait interfers with the Plasmodium parasite in the heterozygous and homozygous recessive genotypes.

Which of these three graphs shows the relationship between sickle-cell anemia and malaria?

Next: How are DNA and RNA related to chromosomes and Mendalian inheritance? The End