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WEEK 6 EXPERIMENT ANSWER SHEET

SUMMARY OF ACTIVITIES FOR WEEK 6 EXPERIMENT ASSIGNMENT

· Experiment 6 Exercise 1 – Monhybrid Crosses

· Experiment 6 Exercise 2 – Dihybrid Cross

· Experiment 6 Exercise 3 – Inheritance of Human Traits

Experiment 6 Exercise 1: Monohybrid Crosses

You will be conducting monohybrid crosses using fruit flies. Open in the following website:

Glencoe-McGraw Hill. No date. Punnett Squares http://glencoe.mcgraw-hill.com/sites/dl/free/0078759864/383934/BL_05.html

Procedure

A. Open the above website and click on the VCR to listen to the introduction. Close the window when done.

B. Click on the Lab Notebook on the lab bench. A breeding scenario will be presented to you that you will need to carry out. Here are the possible phenotypes and genotypes you will using:

a. Normal wings (LL or Ll) or vestigial wings (ll)

b. Gray body (GG or Gg) or black body (gg)

C. Enter the Scenario number in Table 1 below.

D. Based on the Scenario, use the down arrows beneath the Parent 1 and Parent 2 boxes to select the appropriate parents. Look carefully at the flies so that you know which ones to select.

E. Before proceeding, click on the Check Parents button. If necessary, make corrections. If you are correct, the maternal and paternal alleles will be added to the Punnett Square.

F. Next, drag the correct allele combinations and the corresponding fly types to the boxes in the Punnett Square.

G. When you are done, click on Check Offspring. If necessary, make corrections.

H. Record your data in Table 1 below. An example has been given, but note that the example is not using the genotypes and phenotypes used in this exercise.

I. Click on Reset. Repeat steps B – H four more times for a total of five crosses. If a scenario is presented that has already been completed, click Reset again. DO NOT REPEAT a given scenario!

Note that the scenario number you need to record in the Table below is the number associated with the specific scenario you completed.

Table 1. Results of crosses.

	Parent Genotypes	Offspring Genotypes	Offspring Phenotype
Scenario #	Parent 1	Parent 2	#	%	#	%
Example	Rr	rr	2 Rr 2 rr	50% Rr 50% rr	2 red 2 white	50% red 50% white

Questions

1. Which type of cross gave you the greatest number of genotypes? Was the number of phenotypes the same as the number of genotypes or different? If different, why (2 pts)?

2. Can the genotype for a gray-bodied fly be determined? If so, how? (3 pts)?

Experiment 6 Exercise 2: Dihybrid Cross

We will continue to use flies for our crosses, but this time we will examine the inheritance of TWO different traits: body color (gray or black) and wing type (long or vestigial). As with our first crosses, the gray body color is dominant (GG or Gg) over the black body color (gg). And the long wing type is dominant (LL or Ll) over vestigial (ll). Be sure you have reviewed our online Genetics lecture and this week’s reading before proceeding. An example of a dihybrid cross is shown on p 150 in your book.

Recall our flies from the previous exercise. We have the following traits:

· Gray body (GG or Gg) is dominant over black body (gg)

· Long wings (LL or Li) is dominant over vestigial wings (ll)

We will cross a gray bodied fly with long wings which has the genotype GGLl with a gray bodied fly with long wings with a genotype of GgLl . Note that even though the phenotypes are the same, the genotypes of the two parents are different.

Identify the four possible gametes produced by these two individuals. Note that each gamete must consist of two alleles (G or g and L or l):

Parent 1 Parent 2

 

GGLl GgLl

Parent 1 (GGLl) Gametes: _______ ______ _______ _______ (1 pts)

Parent 2 (GgLl) Gametes: _______ ______ _______ _______ (1 pts)

Create a Punnett square to show the outcome of a cross between these two individuals (GGLl and GgLl) using the gametes you identified above (3 pts).

		Parent 1
Parent 2

Questions

1. What are the possible F1 genotypes (these must now have four alleles) and their percentages (4 pts)?

2. Recall that GG and Gg individuals are gray bodied, while gg individuals are black bodied and that LL and Li individuals have long wings, while ll individuals have vestigial wings. What are the phenotypes of the resulting offspring and what are the percentages of these phenotypes (2 pts)?

Experiment 6 Exercise 3: Inheritance of Human Traits

Read over the Inheritance of Human Traits Introduction under the Week 6 Experiment link in our course before beginning.

Procedure

A. For each of the heritable traits describe below, determine which form you have (dominant form or recessive form). This is your phenotype.

B. Record your phenotype information in Table 2 below. Then, enter the possible genotype(s) you have based on your phenotype.

C. Answer the questions found following Table 2 below.

Description of Heritable Traits

Trait	Possible Alleles	Dominant Form	Recessive Form	Examples
Ear lobes	E or e	Detached (Free)	Attached
Hairline	W or w	Widows peak	Straight	Widow’s peak Straight
Tongue rolling	T or t	Able to roll	Unable to roll
Hand folding	R or r	Right thumb on top	Left thumb on top
Chin	C or c	Cleft chin	No cleft chin
Tongue folding	F or f	Can fold tongue backwards	Cannot fold tongue backwards
Thumb	H or h	Straight thumb (cannot bend backwards)	Hitchhiker’s thumb (can bend it backwards)
Little Finger	B or b	Bent inwards	Straight
Mid-digital hair	M or m	Hair on fingers	No hair on fingers

An example is shown as to what should be entered in RED. Please correct the entry for “Ear lobes” based on your personal data. For the Genotypes, please use the letters provided above (8 pts).

Table 2. Your phenotypes and genotypes.

Trait	Phenotype	Genotype
Ear lobes	Unattached OR Detached	EE/Ee OR ee
Hairline
Tongue Rolling
Hand Folding
Chin
Tongue Folding
Thumb
Little Finger
Mid-digital Hair

Questions

1.  Which traits did you have that were dominant (1 pts)?

2.  Which traits did you have that were recessive (1 pts)?

3. What does it mean to be homozygous for a trait? Cite source(s) used (1 pts).

4.  What does it mean to be heterozygous for a trait? Cite source(s) used (1 pts).

5.  Define genotype and phenotype? Cite source(s) used (1 pts).

6.  Which traits do you know for sure that you were homozygous (1 pts)?

1. Marfan syndrome follows a pattern of autosomal dominant inheritance. What is the chance (= probability) that any child will inherit the dominant allele if one parent (Parent #1) does not carry the allele and the other (Parent #2) is heterozygous for it? Provide a clear explanation and complete the Punnett Square below. Be sure to define the letters you use for the two alleles and what the genotypes are of each parent.

 

Citation(s):

 

 

2. Below is a diagram showing the inheritance of an X-linked trait; the first generation is at the top and the third generation is at the bottom. Describe what this pedigree depicts in terms of gender, presence or absence of the disorder, and what feature(s) indicate that the pedigree is for an X-linked trait. 

 

Citation(s):

 

 

3. In one experiment, Mendel crossed a pea plant that bred true for green pods with one that bred true for yellow pods. All of the F1 plants had green pods. What does it mean when an organism like Mendel’s pea plants is true breeding? Which form of the trait (green or yellow pods) is dominant? Explain how you arrived at your conclusion. This should include the possible genotypes of the parents involved in the cross and those of the F1 generation.

 

Citation(s):

 

 

4. What type of mutation has occurred in the DNA of people with sickle cell anemia?  (Look back, if you need to, to see what causes sickle cell.)

 

Citation(s):

 

5. A man who has type B blood and a woman who has type A blood could have children of which phenotypes? Explain your answer; be sure to consider what the possible genotypes are for both parents in your answer.

 

Citation(s):

 

 

6. Unattached earlobes are a dominant trait.  If A denotes the allele for unattached earlobes, and a denotes the allele for attached earlobes, what is (are) the possible genotype(s) of a person who has unattached earlobes?

Could both parents of a person with unattached earlobes have attached earlobes? Why or why not? Think about what the parent’s genotypes have to be.

 

Citation(s):

 

 

7. How are a locus, allele and a gene similar? How would you differentiate among these three terms?

 

Citation(s):

 

 

8. Explain what is meant by polygenic inheritance, pleiotropy, and human gene therapy. Provide an example of each.

 

Citation(s):

 

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Go to SCI: Skin Cancer Investigation and enter the site.  Begin with the Healthy Skin section and read about the three layers of the skin by clicking on the image of the skin on the right. Next answer these questions:

1. What are the types of cells in      the epidermis and how are they related to each other?
2. What is melanin and what is its      role in the epidermis?
3. What is keratin and what does      it do?
4. What are the two primary      features of the dermis?
5. Describe the subcutaneous      tissue.

To continue through the interactive, click on the right arrow at the bottom of the screen to go to the section Effects of the Sun on the Skin and watch the animation about the benefits of the sun and risks of sunlight. Then answer these questions:

1. Name the main benefits of      sunlight.
2. What are some of the benefits      of the sun’s UV rays?
3. How are these rays harmful?

Now go to the section titled Causes and read about how over-exposure to the sun can cause skin cancer. Watch the animation on how normal cells multiply and divide to replace damaged or dead cells. Then answer these questions:

1. How do UV rays affect normal cell      division?
2. Why do some people have a      greater chance of developing skin cancer compared to others?

Continue on to Tumors and answer this question:

1. What are the main differences      between benign and malignant tumors?

Now click on and read the Common Risk Factors. Click on each factor to learn more about the risks. Then answer these questions:

1. What are the five most common      modifiable risk factors of skin cancer?
2. How can where you live increase      your chances of developing skin cancer?
3. How does genetics play a role?
4. What is actinic keratosis?

Now go to the Glowell Clinic: Lab. Click on any patient file where an image of a growth will appear along with the patient’s history.

Review the list of symptoms and check those that describe the growth. Decide whether the growth is cancerous or not. Select the next patient and complete the same steps.

 

Patient

Symptoms

Cancerous?

 

A

 

B

 

C

 

D

 

E

 

F

 

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In this assignment, students will review a microbial journal article.

Choose one article from a primary scientific literature source that uses a microbe as a model organism/system and write a comprehensive summary of the study that answers the following questions:

Choose one article from a primary scientific literature source that uses a microbe as a model organism/system.
NOTE: Many free articles may be obtained from http://www.pubmed.gov or visit the WCU library.

Write a summary of the study that includes:

1. Why did the scientists perform the study (i.e., description of background)?
2. What was the hypothesis (or hypotheses) under investigation?
3. What were the major results and did they support or negate the hypothesis? Which key techniques were used to achieve these results?
4. Why are the results significant and do they point to further/future studies? In other words, why does this article matter and what should or could be done next?
5. Why did you choose this particular article to review? Was it interesting, informative, clearly written, or none of the above?

Compose your review in current APA Style and include:

• A title page
• Answers to the questions above in paragraph format (2 or more pages)
• A reference page with the reference for your article and any other sources used in your review.

 

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The goal of this assignment is to familiarize you with the process going from the characterization of a disease in human patients, to the identification of a mutated gene causing it, to the use of a mouse model to investigate how this mutation is causing the disease. You will learn about the spinocerebellar ataxia 1 (SCA1) genetic disease as an example of such a process.

This assignment is inspired by and uses content from, the lecture “A Healthy Nervous System: A Delicate Balance” on BioInteractive. Watch the video, (it may also be useful to download the transcript for reference) and answer the questions below.

Question 1: Based on this video, describe the symptoms of the SCA1 disease.

SCA1 is a familial disease as indicated by the pedigree analysis chart shown on the video and in the image below.

Question 2: Explain how to read the chart by indicating what the squares and circles represent and what is the difference between filled and hollow shapes.

Question 3: Discuss what conclusions can be drawn from the pedigree eg assuming that the disease is caused by the mutation of one single gene, do you think this mutation is recessive or dominant? Are the affected individuals more likely to be heterozygous or homozygous for this mutation? Is the disease affecting equally men and women? For each conclusion, make sure to explain how it is supported by the pedigree.

The Online Mendelian Inheritance in Man (OMIM) database is a frequently updated database of human genes and genetic diseases.  Search for SCA1 on OMIM. Read quickly through the page to get a general idea of the types of information that can be found on it and how they are presented. Identify the gene whose mutation is responsible for the SCA1 disease, search for it on OMIM and have a quick look at the corresponding page.

Question 4: Based on the descriptions in OMIM and the information from the video, indicate what genetic mutation is responsible for the SCA1 disease and what consequence it has on protein primary structure.

Question 5: Which organ and cell type are primarily affected by the mutation? Is this consistent with the symptoms observed in SCA1 patients?

Mice are generally a good model for human diseases, if you wish, you can read more about the benefits of the mouse model on The Jackson Laboratory website  Advantages of the mouse as a model organism.

Mouse models of SCA1 have been developed and helped researchers to understand this disease and to experiment new treatments.

Question 6: From the video describe the phenotype of the SCA1 mouse. Is it similar to symptoms observed in SCA1 patients?

Question 7: Is SCA1 considered to be caused by a loss of function of the protein affected, or is it thought to be due to another mechanism?

Question 8: Based on the findings from the mouse model, researchers then developed an SCA1 model in Drosophila – what are the advantages of using a Drosophila model over a mouse one

Question 9: Using the Drosophila model of SCA1, what was the protein kinase they found to be implicated in SCA1 associated neurodegeneration and why is this knowledge useful with respect to treating the disease?

 

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The Virtual labs (below) are online laboratory simulations that enable you to perform experiments and observations in microscopy, microbial growth, inheritance, and genetic analysis from the relative comfort of your computer.

Use the Virtual Lab Report form to record your observations and results from these online experiments. When saving your work, title your report with your last name, first initial ‘_V1’. Thus the title for Charles Darwin’s report is DarwinC_V1. Use the ‘Save As’ option to save the file as Word 97 .doc file. Submit the report in the Dropbox before 11:00 PM PST on the second Saturday of class.

      Virtual Lab Report Part I         Due: Second Saturday of the course

 

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