Non-Mendelian Genetics Aim: What are some other ways traits are shown?

Incomplete Dominance A. Both alleles contribute to the phenotype of a heterozygous individual to produce a blending (mixture) of either dominant gene. Example: cross between a red flower & a white flower = pink flower.

Incomplete Dominance B. In incomplete dominance, use capital letter for both traits since they both influence outcome. R W RW Offspring are 100% pink

Incomplete Dominance C. Crossing a hybrid 25% Red 50% Pink 25% White R RR RW WW 25% Red 50% Pink 25% White

Co-Dominance A. Two dominant alleles are expressed at the same time. 1. Results in simultaneous expression of both alleles in the phenotype of a heterozygous individual. Example: Roan cattle w/mixture of red & white hairs; human blood type.

Co-Dominance B. Co-dominance is written with capital letters & superscripts. CR= Red CW= White CRCW= Roan CR CW CRCW

Multiple Alleles A. There may be more than 2 alleles for a trait in a species. 1. Individuals cannot have more than 2 alleles for each trait. Example: Blood type A, B, AB, O

Sex Determination A. Sex is genetically determined at fertilization when a sperm cell containing an X or Y chromosome unites w/ an egg cell containing an X chromosome. 1. XX: produces female 2. XY: produces male

Sex-Linked Traits A. Genes for certain traits are located on the X chromosome. 1. These genes do not have a corresponding allele on the Y chromosome. 2. Many of these genes are recessive therefore they are expressed more in males than females. Example: Hemophilia; colorblindness 3. Females are often carriers.

The Inheritance of Hemophilia

Sex-Linked Traits 4. Pedigree charts are used to show the presence or absence of particular inherited traits in humans.