1. Linkage Groups All the genes on a chromosome are part of one ____________ ___________ _____________ ________ between homologous chromosomes disrupts gene linkage Two genes on the same chromosome that are far enough apart can cross over and provide new gene combinations How does this affect independent assortment?

2. Linkage Groups Two genes are linked and do not assort independently if they are arranged ________ ___________ on the chromosome Genes that are very _______ __________on a chromosome assort independently into gametes The probability that crossing over will occur between two genes and disrupt their linkage is directly proportional to the distance between them *Reference Figure 10.15 in your textbook

3. Genes and the _____________ The environment often influences gene expression The color of floral cluster on yarrow plants will vary depending to the elevation of their habitat Daphnia living in ponds with few predators have rounded head; those living in ponds with many predators have pointed heads Some persons tolerate stress better than others, perhaps due to differences in the gene for a serotonin- transporting protein Different gene-environment interactions are another source of variation in populations

4. Complex Variations in Traits For most populations or species, individuals show rich variation for many of the same traits The phenotype of an individual cannot always be predicted Often, phenotypes fall within a __________________________________________ _________________ _____________: the inheritance of multiple genes that affect a trait

5. Continuous Variation in Populations A given phenotype can vary, by different degrees, from one individual to the next in a population This is the result of interactions with other genes and environmental influences Examples in humans: ___________ and _____________ Bell curves are typical of traits that show continuous variation Distribution around an average Figure 10.19

6. Continuous Variation Figure 10.19 A greater number of genes and environmental factors influencing a trait results in a more continuous distribution

7. Continuous Variation Figure 10.19

8. Regarding the Unexpected Phenotype Tracking even a single gene through several generations may produce results that are different than expected Phenotype results from complex interactions among genes, enzymes, other gene products, and the environment!