Linkage GroupsAll 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?

Linkage GroupsTwo 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

Genes and the _____________The environment often influences gene

expressionThe color of floral cluster on yarrow plants will

vary depending to the elevation of their habitatDaphnia 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

Complex Variations in TraitsFor 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

Continuous Variation in PopulationsA 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 variationDistribution around an averageFigure 10.19

Continuous Variation

Figure 10.19

A greater number of genes and environmental factors influencing a trait results in a more continuous distribution

Continuous Variation

Figure 10.19

Regarding the Unexpected PhenotypeTracking 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!