[h1]How can a Punnett square be used to predict the outcome of a cross between two individuals?[/h1] Follow these directions to answer the Focus Question.

[h2][b]Read: [/b] Learn about the relationship between genes and physical traits and review genetics terminology.[/h2] [b]How can you predict the physical appearance of offspring?[/b] Look at yourself in a mirror. Take a look at your neighbor. Do you look the same? Probably not. But why don't you look the same? It's because of your genes. A person's appearance is determined by many different traits — eye color, nose size and shape, height, etc. Each of these traits is specified by one or more genes. These genes are passed down in successive generations from parent to child. One gene for each trait is inherited from each parent, so you have two genes for each trait. Because no one else has the same combination of genes (unless you have an identical twin), no one else looks exactly like you. Is it possible to predict, in advance, what a child might look like? Punnett squares can be used to show how specific genes might be inherited in offspring. They can also be used to find out the likelihood that offspring might exhibit a particular physical trait. [b]What are genes and alleles?[/b] A [i]gene[/i] is the specific information (sequence of nucleotides) that an organism inherits for a physical trait. [i]Alleles[/i] are variants of specific genes. For example, the gene for freckles has two forms, the F allele and the f allele. The combination of alleles that an organism inherits determines the specific trait that it actually exhibits (for example, freckles or no freckles).

[b]Explore the designated web sites to learn how to create and interpret Punnett squares.[/b] Probability of Inheritance [http://anthro.palomar.edu/mendel/mendel_2.htm] Gene Basics and Glossary of Terms [http://www.genelinkbio.com/gene-basics.shtml] DNA from the Beginning [http://www.dnaftb.org/dnaftb/1/concept/]

Research:

Answer review questions and create a Punnett square. Then, complete and analyze Punnett squares for specific traits. Finally, describe the traits of the resulting offspring and answer the Focus Questions. Print your questions and answer for extra credit! [http://www.sascurriculumpathways.com/ProductEntrance/Launch/launchHandoutPrint.jsp?unit=53]

Respond: