Solved by a verified expert:Virtual Lab: Sex-Linked Traits
Worksheet
1.
Please make sure you have read through all of the
information in the “Questions” and “Information” areas. If you come upon terms that are unfamiliar to
you, please refer to your textbook for further explanation or search the word
here: http://encarta.msn.com/encnet/features/dictionary/dictionaryhome.aspx
2.
Next, complete the Punnett square activity by clicking
on the laboratory notebook. Please be
sure to note the possible genotypes of the various flies:
Female,
red eyes
Female,
red eyes
Female,
white eyes
Male,
red eyes
Male, white
eyes
When you have completed the Punnett square activity, return
to the laboratory scene to begin the actual laboratory activity.
3.
In this exercise, you will perform a Drosophila mating in order to observe
sex-linked trait transmission. Please
click on the shelf in the laboratory.
Here you will find vials of fruit flies.
On the TOP shelf, please click on one of the female vials (on the left
side) and then drag it to the empty vial on the shelf below. Please repeat this step using one of the male
vials (on the right side). These flies
will be used as the parental (P) generation. You may switch your parent choices
at any time by dragging out old selections and dragging in new flies. Use the
Punnett square below to predict the genotypes/phenotypes of the offspring
(Note: refer to the genotype table you
created above if needed):
Genotype:
Phenotype:
Genotype:
Phenotype:
Genotype:
Phenotype:
Genotype:
Phenotype:
___% Female, red eye ___% Female, white eye ___%
Male, red eye ___% Male, white eye
When you are finished, click “Mate and Sort”.
4.
You will now see information appear in the vials
sitting on the next shelf below. These
are the offspring of the parent flies you selected above, and they represent
the first filial (F1) generation. In
your “Data Table” on the bottom of the page and/or on Table I found at the end
of this Worksheet, please input the numbers of each sex and phenotype
combination for the F1 generation. These
numbers will be placed into the first row marked “P generation Cross”.
5.
You will next need to select one of the F1 female flies
and one of the F1 male flies to create the second filial (F2) generation. Drag your selections down to the empty vial
on the next shelf below and fill in the Punnett square below to predict the
offspring:
Genotype:
Phenotype:
Genotype:
Phenotype:
Genotype:
Phenotype:
Genotype:
Phenotype:
___% Female, red eye
___% Female, white eye ___%
Male, red eye ___% Male, white eye
After clicking “Mate and Sort”, you will now have
information on their offspring (the F2 generation) to input into your “Data
Table” or Worksheet below. This
information will be placed into the second row marked “F1 generation Cross”.
NOTE: there are additional lines remaining to use
if your instructor requires the analysis of additional crosses.
6.
Please finish
this exercise by opening the “Journal” link at the bottom of the page and
answering the questions.
Table I:
Cross Type
Phenotype of Male
Parent
Phenotype of Female
Parent
Number of Red eye,
Male Offspring
Number of White
eye, Male Offspring
Number of Red eye,
Female Offspring
Number of White
eye, Female Offspring
P Generation Cross
F1 Generation Cross
P Generation Cross
F1 Generation Cross
Post-laboratory Questions:
1. Through fruit fly studies, geneticists have
discovered a segment of DNA called the homeobox which appears to control:
a. Sex development in the flies
b.Life
span in the flies
c.
Final body plan
development in the flies
2. The genotype of a red-eyed male fruit fly
would be:
a. XRXR
b.XRXr
c. XrXr
d.A
or B
e.
None of the above
3. Sex-linked traits:
a.
Can be carried on the Y chromosome
b.Affect
males and females equally
c. Can
be carried on chromosome 20
d.A
and B
e. None
of the above
4. A monohybrid cross analyzes:
a.
One trait, such as eye color
b.Two
traits, such as eye color and wing shape
c. The
offspring of one parent
5. A
female with the genotype “XRXr”:
a. Is homozygous for the eye color gene
b.Is
heterozygous for the eye color gene
c. Is
considered a carrier for the eye color gene
d.A
and B
e.
B and C
6. In
T.H. Morgan’s experiments:
a.
He concluded that the gene for fruit fly eye
color is carried on the X chromosome
b.He
found that his F1 generation results always mirrored those predicted by
Mendelian Laws of Inheritance
c. He
found that his F2 generation results always mirrored those predicted by
Mendelian Laws of Inheritance
d.A
and B
e. All
of the above
7. In this laboratory exercise:
a.
The Punnett square will allow you to predict
the traits of the offspring created in your crosses
b.XR
will represent the recessive allele for eye color, which is white
c. Xr
will represent the dominant allele for eye color, which is red
d.All
of the above
8. In a cross between a homozygous red-eyed female
fruit fly and a white-eyed male, what percentage of the female offspring is
expected to be carriers?
a. 0%
b.25%
c. 50%
d.75%
e. 100%
9. In a cross between a white-eyed female and a
red-eyed male:
a. All males will have red eyes
b.50%
of males will have white eyes
c.
All females will have
red eyes
d.50%
of females will have white eyes
10. In human diseases that are X-linked dominant,
one dominant allele causes the disease.
If an affected father has a child with an unaffected mother:
a.
All males are unaffected
b.Some
but not all males are affected
c. All
females are unaffected
d.Some
but not all females are affected
Journal
1-i
n a mating between a red-eyed male fruit fly and a red-eyed heterozygous
female, what percentage of the female offspring is expected to be carriers? How
did you determine the percentage?
2-In
a mating between a red-eyed male fruit fly and a white-eyed female fruit fly,
what percentage of the male offspring will have white eyes? Describe how you determined the percentage.
3-Hemophilia,
a blood disorder in humans, results from a sex-linked recessive allele. Suppose that a daughter of a mother without
the allele and a father with the allele marries a man with hemophilia. What is the probability that the daughter’s
children will develop the disease?
Describe how you determined the probability.
4-Colorblindness
results from a sex-linked recessive allele.
Determine the genotypes of the offspring that result from a cross
between a color-blind male and a homozygous female who has normal vision. Describe how you determined the genotypes of
the offspring.
5-Explain
why sex-linked traits appear more often in males than in females.
6-In
humans, hemophilia is a sex-linked recessive trait. It is located on the X chromosome. Remember that the human female genotype is XX
and the male genotype is XY. Suppose
that a daughter of a mother without the allele and a father with the allele
marries a man with hemophilia. What is
the probability that the daughter’s children will develop the disease? Describe how you determined the probability.
7-Colorblindness
also results from a sex-linked recessive allele on the X chromosome in
humans. Determine the genotypes of the
offspring that result from a cross between a color-blind male and a homozygous
female who has normal vision. Describe
how you determined the genotypes of the offspring.
8-Based
on the traits explained in questions 6 and 7, explain why sex-linked traits in
humans appear more often in males than in females.
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