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16. Disinfect your laboratory bench using the bleach
    solution.


17. Wash your hands thoroughly with soap and water.

Analysis

(a) After sufficient time has elapsed, remove your plates

from the incubator and note any changes.

Never open the plates, as any bacterial colonies

within are a potential source of contamination. If

condensation has accumulated on one side of a

plate, try looking through its bottom to observe the

colonies you may have cultured. Once the

experiment has been completed, flood plates with

bleach to kill the bacterial colonies that have been

cultured. Alternatively, place plates in an autoclave

before they are disposed.

Evaluation

(b) Compare your results to your prediction. Explain any

possible causes for variation.

INVESTIGATION 20.1 continued (c) What evidence is there to indicate that protein was

synthesized by the bacteria?

(d) Why was it important to streak out both types of

bacteria on both types of plates?

(e) This experiment contains both positive and negative

controls. Identify them. What information do the

controls provide in this experiment?

(f ) Why was it important to cool the inoculating loop

before obtaining a bacterial colony from a stock plate?

(g) Why was it important to resterilize the inoculating

loop between transfers of bacteria?

(h) Suggest possible sources of error in this procedure

and indicate their effect on the results.

Synthesis

(i)E. colistrains containing the genetic sequence pAmp

are resistant to ampicillin. Research how the

ampicillin can be deactivated by -lactamase, the

protein coded for by the ampicillin-resistance gene.

(j) Predict what would happen if there was an error in

the genetic sequence that codes for -lactamase.

Restriction Enzyme Digestion of

Bacteriophage DNA

In this investigation, bacteriophage lambda DNA will be

digested using the restriction endonucleases EcoRI,HindIII,

and BamHI. The fragments produced will be separated using

gel electrophoresis. Fragment sizes will be calculated from an

analysis of the agarose gel. Bacteriophage lambda DNA is

obtained from a virus that infects bacterial cells and is 48 514

base pairs in length.

Before you begin, predict the number and size of the DNA

fragments you will obtain, using the restriction enzyme site

map shown in Figure 1on the next page.

Problem

How do the patterns of DNA fragments compare when a piece

of DNA is digested using different restriction endonucleases?

Materials

safety goggles

gloves

70 % ethanol solution (or 10 % bleach)

4 1.5 mL Eppendorf tubes

waterproof pen for labelling

masking tape

polystyrene cup

freezer

crushed ice

20 L of 0.5g/L lambda DNA

5 L 10restriction buffer

1.0–20 L micropipette with tips

2 L each ofBamHI,EcoRI, and HindIII restriction

endonucleases

Purpose Design Analysis

Problem Materials Evaluation

Hypothesis Procedure Synthesis

Prediction Evidence

INVESTIGATION 20.2 Report Checklist

696 Chapter 20 NEL