DNA Electrophoresis Genetics Disorder Lab

*Safety goggles should be worn during lab.  Put them on (over your eyes, not on your forehead) when instructed and keep them on until told to take them off.

For the next several days you will take the role of genetic counselor. Your job is to analyze DNA samples from couples who are planning to have children.  You must decide if each couple has an increased chance of giving birth to a child with a genetic disorder.

The couple you are currently counseling (Todd and Mary Spellman) have some family members who died from Cystic Fibrosis (CF).  They fear that if they have children they might also be stricken with this disorder.  At the end of this lab you must tell the Spellman’s what the chances are that their child will develop the disorder and make a recommendation of wither or not to have children.

Day 1: You have received DNA samples from 2 individuals in the Spellman’s family.  You must prepare them to be analyzed.

1.     Draw up 10ul of restriction enzyme form the tube labeled “Buffer for EcoRI.”  Use a new tip each time you use the micropipette.  Expel the liquid into ONE of the DNA samples you received then discard the tip.

2.     Put on a new tip and add 10ul of enzyme to the other DNA sample.

3.     Flick the side of the tubes gently with your finger to mix.

4.     Place the tubes in a 37 degree C heating block for 30-40 minutes.

Day 2:  Your DNA samples have been “digested” by the enzyme.  Now it is time to run the samples.

1.     Add 5ul of 6X loading dye to each tube (from yesterday) using a micropipetter.

2.     Load 20ul of each sample into separate wells of the gel.  Carefully support the pipette with two hands and expel the sample into the well.  Keep the button pressed down until you have removed the pipette from the well.  Discard the tip after every sample.

3.     Record which well you put your samples into

4.     The teacher will now “run” the gels by running electrical current through the box.  This will take 30-40 minutes.

(*in one well a standard has been added.  This contains DNA pieces of known size)

Day 3:  The samples have been run.  Now it is time to analyze the results

1.     Look at the gels.

2.     Draw (on the chart on the board) the bands you see in your samples.

3.     Draw the gel (what is on the board) on the back side of this sheet and label all wells.

4.     Look at all the samples on the board and compare them to the pedigree of the family.  What conclusions can you make from this information?

5.     Use the information on the board and the pedigree to determine the phenotype and genotype of all 16 individuals

Phenotype                              Genotype

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

 
Assume that Todd is heterozygous for CF.  Use a Punnett square to determine the odds that a child will have CF. 
(See lab sheet for larger Scernario 2 Phenotypes)

Based on what you have seen, what is your recommendation to the Spellman’s?  Should they have children or not?  Explain why in a paragraph (introduction, 3 supporting, conclusion).