Scientific Method & Genetics

 

Using the Scientific Method With Genetics

 

Introduction:

Humans are classified as a separate species because of all the special characteristics that they possess. These characteristics are controlled by strands of DNA located deep inside their cells. This DNA contains the code for every protein that an organism has the ability to produce. These proteins combine with other chemicals, within the body, to produce the cells, tissues, organs, organ systems, and finally the organism itself. The appearance of these organs, such as the shape of ones nose, length of the fingers, or the color of the eyes is called the phenotype.

Even though humans contain hands with five fingers, two ears, or one nose, there are subtle differences that separate these organs from another. There are subtle differences in a person’s genes that allows for these different phenotypes. In this lab, we are going to observe some of these differences in phenotype. All human hands look pretty much alike, but there are genes on your chromosomes that code for the characteristics making up your hand. We are going to examine two of these characteristics (hand width and hand length) and try to determine why these phenotypic differences occurred.

Materials:

• metric ruler (see end of lab)
• pencil
• calculator

Procedures:

Day 1

1. Choose a partner and have them measure the length of your right hand in centimeters. (Measure from the tip of your middle finger to the beginning of your wrist as shown in figure 1.)  Record your measurements in Table 1.
2. Now measure and record the length in centimeters of your partners hand.
3. Have your partner measure the width of your right hand, straight across the palm, and record the data in Table 1. (see figure 1.)
4. Now measure & record the width of your partner’s hand.

Figure 1.

Table 1

5. After the entire class has completed Table 1, record your group data on the Class Data Table at the front of the room
6. Record the Class Data Table information on your lab sheet’s Table 2.

Table 2

Click for Class Data Table

Day 2

7. In order to form a more accurate conclusion, the collection of additional data from several classes is necessary. Using the Class Data Tables for each period at the front of the room, record the # of males and # of females having the same length hand in Table 3.
8. Only record a hand length (e.g. 18.1 cm) once on table 3.

Table 3:

9. Using the Class Data Tables for each period at the front of the room, record the # of males and # of females having the palm width in Table 4.
10. Only record a palm width (e.g. 15.3 cm) once on table 4.

Table 4:

11. Line graph data from table 3 using hand length as your independent variable and the number of times (total males & females) that measurement appeared as the dependent variable.
12. Make a second line graph using data from table 4 using palm length as your independent variable and the number of times (total males & females) that measurement appeared as the dependent variable.
13. Be sure to include a title for each graph and label the x and y axis and include their unit of measurement.

Graph Title: ___________________________________________________________

Graph Title: ___________________________________________________________

Analysis:

1. Examine the above graphs. What is the shape of the line for hand length?  for the palm width?

2. What is the most abundant measurement (mode) for hand length?

3. What was the average hand length (mean) for males?   for females?   for total students?

4.  What is (are) the least abundant measurement(s) for hand length?

5. What is the most abundant measurement (mode) for palm width?

6.  What is the least abundant measurement  for palm width?

7. What was the average palm width (mean) for males?   for females?   for total students?

8. Are there any similarities in the graph of the above two characteristics and if so, what are they?

9. Are there any differences in the graph of the above two characteristics and if so, what are they?

10. Is there a difference in the length of the male and female hand?

11. Is there a difference in the width of the male and female hand?

12. Does gender have an effect on the phenotype of a trait? Explain.

Cut and use: