Virtual Genetics Lab
Prior to lab you should understand:
• How dominant alleles and recessive alleles can be experimentally distinguished using
reciprocal genetic crosses.
• How autosomal genes and sex-linked genes can be experimentally distinguished using
reciprocal genetic crosses.
I. Objective:
•
•
•
Conduct genetic crosses to determine if a trait is dominant or recessive.
Conduct genetic crosses to determine if a trait is controlled by an autosomal
or sex-linked gene.
Conduct genetic crosses to determine the genotype of individuals.
II. Background:
Virtual Genetics Lab (VGL) is a computer program designed at the by Brian White at the
University of Massachusetts Boston. It simulates a simple genetic system by allowing you to
conduct simple crosses to investigate the genetics of simple traits of a virtual creature. In this
simulation you choose which individuals to mate; you decide how many time you have to mate
them and how many offspring you need to observe. By conducting a series of genetic crosses,
you will develop a “genetic model” for the trait you are investigating. Which trait is dominant?
Is the trait sex-linked?
At the beginning of the simulation you are given a cage of virtual flies collected in the field. The
cage contains both male and females. The population of flies differs for one trait of several
traits. For example if the trait is body color you will have both red and green creatures. All the
traits in VGL are controlled by a single gene with a dominant and recessive allele. The gene
may be autosomal or sex linked. Because the flies were capture in the wild, they may be
homozygous, heterozygous or even hemizygous. You can select any male and female from a
cage and mate them to generate a cage of progeny which you can analyze for the trait.
III. Using VGL
The class will meet in the computer lab, SC358. You will be given a CD-ROM containing the
VGL program and a series of populations to analyze. To start the VGL program double-click the
program icon.
A Virtual Genetics Lab window will appear on the screen. To open a population cage click the
“file” icon at the top of the window
File Icon
(Open Work)
When you double-click on the file icon, a dialogue box will open that contains a list of
populations.
You can select a population to work on by double clicking on that population. For example you
can see the cage for population 25 by double clicking on the file.
Note that cage 1 contains 31 individuals. 16 flies have green eyes and 15 flies blue eyes. Also
there are 15 males and 16 females. Remember that these flies are caught from the wild. They
may be homozygous, heterozygous or even hemizygous. You may need to conduct multiple
crosses to determine which trait is dominant, if the trait is sex-linked and to determine the
genotypes of individual flies.
To help keep track of the flies, each fly has been assigned a number. You can see the assigned
numbers at the top of the data collection sheet. You will use these numbers to keep track of your
matings. See example below for population 25 (Also look at the last page of these instructions
for an example data collection sheet).
# assigned
to each fly
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Sex Icon
To conduct a cross you must select a male and female fly. To select a fly, simply click on the
for Fly #2
sex icon of that fly. For example, select fly #2 by clicking on that fly. Notice that when you
click on a male fly, the icon turns blue, when you click on a female fly the icon turns red. Select
fly # 2 and #26
After you have selected a pair of flies you can mate them. To mate the flies, click on the “cross”
icon at the top of the VGL window.
Cross Icon
for mating
A second cage of progeny flies will appear on the screen. It sill look something like the cage
below. However, because of random fertilization, no two matings will generate the exact same
set of progeny.
Not every cross will provide you with information about the genetics of your trait. You will need
to conduct a series of crosses to complete any data collection sheet.. Be sure to record the results
of all your crosses before proceeding with other crosses. There is a table on the data collection
sheet where you can enter the data. (see example below)
Parents
Cross
Male
1
#2
Phenotypes of Progeny
Green
Blue
Female
♂
♀
♂
♀
#26
10
9
11
9
Comments
One parent may be heterozygote
IV. Materials:
CD-ROM containing VGL Program and 10 populations
of flies
4 Data collection sheets corresponding to 4 of the 10
populations. (Each student will get a different
set of populations)
V. Procedure:
3. Choose one of your data collections sheets
4. Identify which population is described on that
sheet.
5. Run the VGL program by double clicking on the
fly icon.
6. Click on the “file” icon to open the population.
7. Once you have a population cage, conduct
appropriate crosses to determine which trait is
dominant, whether the trait is sex-linked, and the
genotype of the individuals noted at the bottom
of the data collection sheet.
VI. Short Report
1. Complete the four data collection sheets.
2. Staple them together, write you name on the top
sheet. Short reports are due at the end of lab.
Example Data Collection Sheet
Population 25
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Which trait is dominant? __________________________
Is this trait autosomal or sex linked? ______________________________
Outline the crosses and summarize the data that supports you conclusion.
Parents
Cross
Male
Female
Phenotypes of Progeny
Green
Blue
♂
♀
♂
♀
Comments
Determine the genotypes for the following flies
4 ______
16 ______
28 ______
8 _______
20 ______
30 ______
12 ______
24 ______