Download Biology 164 Laboratory CATLAB: Computer Model for Inheritance of

Biology 164 Laboratory
CATLAB: Computer Model for Inheritance of
Coat and Tail Characteristics in Domestic Cats
(Based on simulation developed by Judith Kinnear, University of Sydney, NSW, Australia)
Introduction
CATLAB is a computer program that allows you to mate domestic cats, selected on the basis of coat
color and pattern, and the presence or absence of a normal tail. The program then produces genetically
valid litters of kittens. You will observe the phenotypes of these kittens, and you may run subsequent
crosses.
The program covers an extensive range of color and pattern variants, as well as tail variants, present
among non-pedigreed domestic cats. Initially, you will make crosses between unrelated cats; after the
first cross, however, you may request crosses between any existing cats, e.g., crosses between offspring
or backcrosses of offspring to parents. In addition, you may introduce unrelated cats into the breeding
program at any stage.
CATLAB is open-ended and simply acts as a vehicle for your genetic investigations. In general the
problem to be investigated, the starting point, the sequence of investigations, and the finishing point can
all be defined and controlled by you. The important outcome of your using this program is, in many
cases, not so much the conclusions reached, but the appropriateness of the procedure used and the
validity of the scientific reasoning behind the procedures.
You will use CATLAB to determine the inheritance mechanisms of some of the genes controlling coat
and tail characteristics in non-pedigreed domestic cats. After observing the progeny from crosses you
design, you will formulate a hypothesis to explain the inheritance mechanism of a given trait, and test
your hypothesis using Chi-square analysis. Finally, you will draw conclusions based on your analysis.
You will begin working on these problems in lab today, and turn in the remaining problems as
homework that is due at the beginning of lab next week.
Objectives
To develop your skills in assigning genotypes, specifically in planning crosses capable of producing
relevant data and interpreting experimental results.
To extend your understanding of genetic ratios, specifically their probabilistic nature and sensitivity to
sample size, and your ability to use this knowledge in predicting possible outcomes of crosses.
To help you learn to recognize the distinguishing features of inheritance of mono-genetic traits:
dominant/recessive/incomplete, autosomal/sex-linked.
To develop your skills in planning strategies appropriate for analyzing inferred genetic phenomena such
as linkage, gene interaction, and lethality.
To develop your skills in formulating genetic models consistent with and sufficient to explain the
observed outcome of breeding experiments, and then to test your genetic models.
CATLAB
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Coat and Tail Characteristics Recognized in CATLAB
Pattern in this program refers to the arrangements of stripes on those cats commonly known as tabby
cats. Two patterns are recognized in CATLAB:
- mackerel tabby, with parallel stripes on the cat's flanks;
- blotched tabby, with wide swirling stripes.
Some cats, of course, have no tabby pattern, for example, a black cat or a gray and white cat.
Color in this program refers to the colors visible on the cat's coat. The colors commonly seen in cats and
included in CATLAB are black, gray, orange, cream and white. Cats may be a single color (all-white,
all-black) or they may be a combination of colors (black and white, black and orange [also known as
‘tortoiseshell’], gray and cream).
The program classifies cats that are partly white into two groups:
- “with some white” where less than half the coat is white;
- “with extensive white” where half or more of the coat is white.
Cats classified as "with some white" usually have white restricted to their feet, belly, neck and face.
The program assigns tabby cats the color of their dark stripes, not the color of their lighter backgrounds.
Therefore, a black mackerel tabby has black stripes on a pale background.
You should make sure you are familiar with the coat colors and patterns of cats. Review photographs of
cats exhibiting different coat colors and patterns. If possible, observe these traits in real cats.
The presence or absence of a tail is recognized in CATLAB. Most cats, of course, have tails, but some
have an inherited lack of tail. These are called Manx cats.
CATLAB
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A Quick Tour of the CATLAB Software
Click OK on the title screen to display the simulation screen and the program's controls
The left panel lists the cats you added and their offspring. The right panel contains help screens. Either
panel can be moved to enlarge the other.
The menu bar across the top consists of:
File
Cat
Options
Use the options under each menu to select and mate the cats for your investigations. The icons under the
menu bar are shortcuts to use once you are familiar with the operation of the program.
Cat Menu:
Add a cat with the characteristics of your choice.
Set as Parent allows you to select a male and a female for mating.
Set Litter Size controls the litter size (4 to 7) or allows a random size between 4 and 7.
Mate Cats produces a litter form the selected parents.
Display Phenotype shows a simple graphic of the selected cat's characteristics and an image of its
phenotype.
At this point, try adding a cat. Under the Cat menu, select Add. Select Female, Has a tail and Not allwhite by checking the buttons next to those choices. Click Next. Select No white areas. Click Next. Select
Mackerel and Orange. Note the cat graphic with the chosen features and the text description. Click
Finish. Your cat is now listed on the cat list. Click on the cat's number at left. Form the Cat menu, select
Display Phenotype. Graphic, text description and image will be displayed.
Options Menu:
Chi-Square statistical test option.
Toolbar displays a row of icons used as shortcuts when using the program.
Status Bar describes the option selected in the Menu Bar or by clicking an icon button.
Sound turns sound off or on.
CATLAB
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Toolbar Shortcuts
Beneath the menu bar is a row of buttons (toolbar) that are shortcuts to perform a flinction without going
through the menu bar. An active button has a dark letter or graphic within it.
Form left to right, their functions are:
1. (N) Start new investigation with the option to carry forward selected cats.
2. (Printer Icon) Print the cat list.
3. (+) Add a cat with characteristics of your choice.
4. (P) Choose a cat as a parent for the next litter.
5. (L) Set litter between 4 and 7 or random (4-7).
6. (M) Mate the selected male and female.
7. (Cat Icon) Display a simple graphic, text description and image of the selected cat.
8. (x 2) Chi-Square statistical test.
Select Add by clicking "+"in toolbar. Select Male, Lacks a tail and All-white. Click Finish. Click on
the number] of the first cat, then click "P "for Set as Parent in toolbar. Click on the number 2 cat and
then select it as parent also. "Mom" and "Dad" appear on the left. Jn the toolbar, click Litter Size. Make
your choice and click OK To mate the selected cats, click "M" in toolbar. A box appears with graphics
of the litter. Click OK The litter is then added to the Cat list. Select other parents and mate them to
continue your investigation.
NOTE: The characteristics in each column can be sorted by clicking the column title, Parents, Sex, etc.
The Color column is sorted consistent with the underlying genetics - strong color followed by its dilute
equivalent:
1.
2.
3.
4.
All-white
Black, Gray (dilute)
Orange, Cream (dilute)
Orange and Black, Cream and Gray (dilute)
This results in sorted lists that help identify the several genes that are responsible for color - All-white,
Orange and Density.
Other Pertinent Facts Related to Use of CATLAB
The model is based on seven loci, one locus controlling the presence of tail, the other six loci
responsible for coat characters. Allelic frequencies from average gene pools were used in the model.
Among the seven loci, some are functionally interdependent, i.e., epistatic.
One locus has a lethal phenotype.
One locus is sex-linked.
All input and output of program is at the level of phenotype.
CATLAB
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CATLAB PROBLEM SET
For each problem you will formulate a hypothesis to explain the mechanism of inheritance of the trait(s) under
question, and then design one or more crosses to test your hypothesis. Fill out a CATLAB DATA SHEET for
each cross you design. Use as many data sheet pages as are required to reach a satisfactory conclusion regarding
the inheritance of the trait you are studying, but be sure to number the pages carefully so that your lab instructor
can follow the progression of your investigation. Your conclusions must be supported using Chi-square analysis.
Problem 1
In cats ‘cream’ coloration is a dilute version of ‘orange’ (ginger), while gray is a dilute version of black. Whether
or not a color is diluted is controlled by the D locus. Using only orange or cream colored cats, determine the
inheritance mechanism of the D locus. Hint: since orange or cream coloration is only expressed in tabby cats, use
only orange blotched or cream blotched cats in your crosses.
Problem 2
The S locus controls the degree of white spotting. Choose parents of gray color that differ in terms of the degree
of white spotting. Determine the inheritance mechanism of the S locus.
Problem 3
Orange color in non-pedigreed cats is controlled by the O locus. The non-orange phenotype, if not diluted,
appears as black coat color. Perform the following reciprocal crosses:
Orange blotched female X black blotched male
Black blotched female X orange blotched male
What conclusions can be drawn regarding the inheritance mechanism of the O locus. Hint: ignore the tabby
pattern in the result.
Problem 4
The absence of a tail in cats is known as the Manx condition, and is controlled by the M locus. What can you
conclude about the inheritance pattern of the M locus. Note: you must generate at least 75 offspring when
performing Chi-square analysis.
Problem 5
The tabby patterns, mackerel or blotched, are controlled by the T locus. Devise a series of crosses to determine if
there is linkage between the D locus (controlling dilution of color) and the T locus. Note: Only use black and
gray colors. Disregard any non-tabby cats when performing Chi-square analysis. Hint: first establish dominance
relationship of the T locus, then devise a cross that will result in an offspring that is known to be a heterozygote
for both the T locus and D locus. Perform a test cross by crossing this heterozygote to an individual that is
recessive for both loci.
CATLAB
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