‘ genotype display options ’ ∙ select ‘ single letter ’ 3 H u m a n i t i e s

‘ genotype display options ’ ∙ select ‘ single letter ’ 3 H u m a n i t i e s

1. Selecting an Experiment

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select Single Gene Inheritance
∙ Select one of the options for the phenotypes

A monohybrid cross examines only one gene. Two parents will appear in the
‘Parents’ box. In most of these experiments, both parents are true-breeding or
homozygous for their genotype (e.g. ++X bb). In these preliminary experiments the
genotypes will be displayed, but you won’t see them in your assigned experiments.
The mutant allele may be recessive or dominant to the wild type and may be on an
autosome or the X chromosomes (sex-linked gene).

2. Setting the Options

Before you start working on any of the sample problems or your assigned experiments,
do the following so the alleles for your various genotypes are displayed by a single
letter:

∙ Click on ‘Options’
∙ Then click on ‘Genotype Display Options’
∙ Select ‘Single Letter’

3. Observing the Parents’ Phenotypes

To examine the phenotypes of the parents:

∙ Click on the first parent or drag it to the ‘Observation Platform’
∙ The fly will appear enlarged so you can observe it for mutations

∙ Don’t forget to use the bristles magnifying glass to observe the bristles more
closely
∙ Record any traits that are not wild type
∙ When you are finished with your observations, click on the parent or drag it back to
the ‘Parents’ box. Note: if you put a fly in the ‘Morgue’, it is gone for good; you cannot
get it back

∙ Click or drag the second parent to the ‘Observation Platform’ and do likewise

4. Breeding the F1 Generation

∙ Return the parent flies to the ‘Parents’ box (if necessary)
∙ Click on the ‘Breed arrow. F1 flies will appear in the ‘Offspring’ box

5. Preparing the F2 Generation

∙ While counting the F1 offspring phenotypes, be sure to drag an F1 male and an F1
female to the ‘Holding Jar’. Choose the first male and first female you see so that you
don’t forget

6. Counting the F1 Offspring’s Phenotypes

∙ Click on an offspring or drag it to the ‘Observation Platform’ and record its
phenotype
∙ In this simple cross, all of the F1 flies are identical, but this won’t always be
the case. In other words, in later experiments you will need to observe the
phenotypes of many F1 flies to get the correct F1 ratios (~100

flies)
∙ To observe the next F1 fly, just click on ‘Observe’ arrow. This will send the current fly to

the ‘Morgue’ and more the second F1 fly to the ‘Observation Platform’. Don’t forget to
drag an F1 male and an F1 female to the ‘Holding Jar’ to breed for the F2 generation

7. Breeding and Counting the F2 Generation

∙ Click the ‘Empty’ button under the ‘Parents’ box to send the original parents
to the ‘Morgue’
∙ Drag your two F1 flies from the ‘Holding Jar’ to the ‘Parents’ box
∙ Click the ‘Breed’ arrow

∙ Tally the phenotypes in the F2 generation by observing the offspring. Count F2 flies
until you feel that you have a sufficient number for a good ratio (~100 flies)

8. Genetic Hypothesis and Chi Square Test

With the F1 and F2 ratios, you should be able to come up with a genetic explanation
for the data. For example, if you got a 3:1 ratio for wild:mutant in the F2 generation,
your hypothesis might be: “The wing mutation is caused by an allele on an
autosomal chromosome that is recessive to the wild type allele.” Next, you would
test your hypothesis with a Chi Square test. When you are finished with the first
monohybrid experiment click ‘Reset’

9. Try a Dihybrid Experiment

This is the same process as for the monohybrid experiment, but now you are dealing
with two separate, unlinked genes. Both genes are on the autosomal chromosomes.

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select Double Gene Inheritance

∙ Select one of the options for the phenotypes

These parents have mutations in two genes, so find what traits have the mutations
and then repeat the same process as for the monohybrid experiment (steps 3-8).
Write your observations. Once you have finished with the dihybrid experiment, move
on to one of the experiments involving a sex-linked gene.

10. Try an Experiment with a Sex-linked Gene

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select X-Linked Inheritance
∙ Select one of the options for the phenotypes

For genes located on the X chromosome, it is typical and easier to following the
traits if you actually write down the allele AND the corresponding sex chromosome,
e.g. XW or xW. Y- means that there is no allele on the Y chromosome. Experiments 8
and 9 show incomplete dominance and you may wish to check these out as they
are unique.

Find what traits have the mutations and then repeat the same process as for the
monohybrid experiment (steps 3-8). Write down your observations.

11. Report your findings

Pretend you did this in a real life laboratory setting. Compose a lab report (5 pages maximum),
with an introduction, methods section, results section, and discussion section.1. Selecting an Experiment

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select Single Gene Inheritance
∙ Select one of the options for the phenotypes

A monohybrid cross examines only one gene. Two parents will appear in the
‘Parents’ box. In most of these experiments, both parents are true-breeding or
homozygous for their genotype (e.g. ++X bb). In these preliminary experiments the
genotypes will be displayed, but you won’t see them in your assigned experiments.
The mutant allele may be recessive or dominant to the wild type and may be on an
autosome or the X chromosomes (sex-linked gene).

2. Setting the Options

Before you start working on any of the sample problems or your assigned experiments,
do the following so the alleles for your various genotypes are displayed by a single
letter:

∙ Click on ‘Options’
∙ Then click on ‘Genotype Display Options’
∙ Select ‘Single Letter’

3. Observing the Parents’ Phenotypes

To examine the phenotypes of the parents:

∙ Click on the first parent or drag it to the ‘Observation Platform’
∙ The fly will appear enlarged so you can observe it for mutations

∙ Don’t forget to use the bristles magnifying glass to observe the bristles more
closely
∙ Record any traits that are not wild type
∙ When you are finished with your observations, click on the parent or drag it back to
the ‘Parents’ box. Note: if you put a fly in the ‘Morgue’, it is gone for good; you cannot
get it back

∙ Click or drag the second parent to the ‘Observation Platform’ and do likewise

4. Breeding the F1 Generation

∙ Return the parent flies to the ‘Parents’ box (if necessary)
∙ Click on the ‘Breed arrow. F1 flies will appear in the ‘Offspring’ box

5. Preparing the F2 Generation

∙ While counting the F1 offspring phenotypes, be sure to drag an F1 male and an F1
female to the ‘Holding Jar’. Choose the first male and first female you see so that you
don’t forget

6. Counting the F1 Offspring’s Phenotypes

∙ Click on an offspring or drag it to the ‘Observation Platform’ and record its
phenotype
∙ In this simple cross, all of the F1 flies are identical, but this won’t always be
the case. In other words, in later experiments you will need to observe the
phenotypes of many F1 flies to get the correct F1 ratios (~100

flies)
∙ To observe the next F1 fly, just click on ‘Observe’ arrow. This will send the current fly to

the ‘Morgue’ and more the second F1 fly to the ‘Observation Platform’. Don’t forget to
drag an F1 male and an F1 female to the ‘Holding Jar’ to breed for the F2 generation

7. Breeding and Counting the F2 Generation

∙ Click the ‘Empty’ button under the ‘Parents’ box to send the original parents
to the ‘Morgue’
∙ Drag your two F1 flies from the ‘Holding Jar’ to the ‘Parents’ box
∙ Click the ‘Breed’ arrow

∙ Tally the phenotypes in the F2 generation by observing the offspring. Count F2 flies
until you feel that you have a sufficient number for a good ratio (~100 flies)

8. Genetic Hypothesis and Chi Square Test

With the F1 and F2 ratios, you should be able to come up with a genetic explanation
for the data. For example, if you got a 3:1 ratio for wild:mutant in the F2 generation,
your hypothesis might be: “The wing mutation is caused by an allele on an
autosomal chromosome that is recessive to the wild type allele.” Next, you would
test your hypothesis with a Chi Square test. When you are finished with the first
monohybrid experiment click ‘Reset’

9. Try a Dihybrid Experiment

This is the same process as for the monohybrid experiment, but now you are dealing
with two separate, unlinked genes. Both genes are on the autosomal chromosomes.

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select Double Gene Inheritance

∙ Select one of the options for the phenotypes

These parents have mutations in two genes, so find what traits have the mutations
and then repeat the same process as for the monohybrid experiment (steps 3-8).
Write your observations. Once you have finished with the dihybrid experiment, move
on to one of the experiments involving a sex-linked gene.

10. Try an Experiment with a Sex-linked Gene

∙ At the top of the screen, select Labs to go back to the main menu
∙ Select X-Linked Inheritance
∙ Select one of the options for the phenotypes

For genes located on the X chromosome, it is typical and easier to following the
traits if you actually write down the allele AND the corresponding sex chromosome,
e.g. XW or xW. Y- means that there is no allele on the Y chromosome. Experiments 8
and 9 show incomplete dominance and you may wish to check these out as they
are unique.

Find what traits have the mutations and then repeat the same process as for the
monohybrid experiment (steps 3-8). Write down your observations.

11. Report your findings

Pretend you did this in a real life laboratory setting. Compose a lab report (5 pages maximum),
with an introduction, methods section, results section, and discussion section.