Heredity+Inquiry

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 * GENETIC VARIATIONS IN HAND SPAN SIZE**

RICHARD CHILTON               CHICAGO VOCATIONAL HIGH SCHOOL 2100 EAST 87TH STREET CHICAGO, IL                              1-312-978-1600

Students shall measure their handspan size to determine if one pair or many pairs of genes control that trait.
 * OBJECTIVE:**

Metric rulers, Basketball, Lab. Worksheet, Graph paper, and Graphic overlays.
 * MATERIALS:**

Obtain a metric ruler, lab. worksheet and graph paper. Measure your handspan size as demonstrated by teacher, spreading out your hand on a sheet of paper. Draw a line from the tip of your thumb to the tip of your little finger. Do not include length of fingernails. Measure the length of the line (your handspan) in millimeters. Record the measurements of all members of your class on the chalkboard. Organize the measurements into a graph showing handspan size in groups of 5 mm. Also record the number of students in each group. Draw a graph of the data in the table. Then carry Basketball out to students to see if students can place handspan across the Basketball and hold in place without touching any object. Next, answer the following questions:
 * STRATEGIES:**

(1) What does the graph reveal about the differences in handspans within your class?

(2) Based upon these data, do you think size of handspan size is controlled by one or more pairs of genes?

(3) What other factors can affect hand size?

then class results would usually show only two categories or groups. When a genetic trait is controlled by several pairs of genes, a number of different groups will appear. Therefore, this genetic trait must be controlled by more than one pair of genes.
 * Conclusion:** If a genetic trait is controlled by a single pair of genes,

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