Complex Patterns of Inheritance

1. Incomplete Dominance The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

2. Codominance Both alleles are expressed in the heterozygous condition. Example: -Changes in hemoglobin cause red blood cells to change to a sickle shape. -People who are heterozygous for the trait have both normal and sickle-shaped cells.

Cross two people that carry an allele for normal cells and an allele for sickle cells. Notice all are represented by capital letters. N S NN NS SS What type of cells would each individual have?

3. Sex determination Sex chromosomes determine gender. Non-sex chromosomes are called autosomes.

-The X chromosome contains genes for many traits, while the Y chromosome only carries a few genes related to the development of male characteristics. -Traits that are carried on the X chromosome are called sex-linked or X-linked. Examples of x-linked traits include hemophilia and red-green color blindness.

Cross a non-colorblind female with a non-colorblind XN Xn XN XN XN Xn Y XNY Xn Y What is the genotypic ratio? What is the phenotypic ratio?

4. Multiple Alleles More than two alleles are possible for a given trait. Example: Human blood type – there are three possible alleles: A B O

Blood Cross IA IB IAIB IB IB i IAi IBi What is the genotypic ratio? What is the phenotypic ratio?

Example – Coat color in rabbits Multiple alleles can demonstrate a hierarchy of dominance. In rabbits, four alleles code for coat color: C, cch, ch, and c. What can you learn from the way that the alleles are written? Rabbits – light gray, dark gray, chinchilla, albino, himilayan

5. Linkage Group – When genes are located on the SAME chromosome they are said to be in a linkage group. -In a linkage group the genes travel together during meiosis and therefore do not follow the Law of ________________. -Linkage groups can be broken during the process of _________________ while meiosis occurs. -The closer together genes are on a chromosome, the less likely that they will . . .

6. Polygenic traits Traits where multiple pairs of genes control the trait. What other traits may be polygenic?

7. Pedigree -A diagram that traces the inheritance of a particular trait through several generations