Can We Change Our Genes?

Analyze and investigate emerging scientific issues. For example, genetically modified food, stem cell research, genetic research and cloning.


Genetic Issues

What if you could grow yourself a new arm? What if you knew exactly what disease you might get in 40 years? What if you had a clone 15 years younger than you who you could teach to do things differently than you did?

Dolly, the sheep, and her clone

Genetics is a relatively new field of scientific study, only having been around for about the last 60 years. With new technology, scientists are able to do more and more to help improve our lives, but they are often controversial. Cloning can result in new organs, stem cells can be used to do research on many diseases, the DNA of our food can be changed so that it grows better, and genetic research can tell us what diseases we or our offspring might develop.

It is important to stay informed of these issues because they will form many of the political and ethical issues of the future, if not the present! Many people take a side on these issues based on fear and misinformation; if you understand what these issues are actually about, you can make more informed decisions that could ultimately lead to a better life for you and your children.

Cloning is not all about making copies of oneself. Scary movies and sci-fi television series would have us believe that scientists would like to make armies of super-intelligent humans that could dominate the entire world. However, that’s completely untrue! Cloning is mainly the use of DNA to make organs that can be used to treat diseases and to replace organs that have failed. If someone has a heart attack and needs a new heart, their own DNA could be used to create that new organ!

As we have previously seen, a zygote starts dividing and the cells differentiate. This power to divide into any other cell of the body is used by scientists in stem cell research. Stem cells can be taken from aborted embryos, but can also be taken from adult cells through often complicated and painful procedures through the bone marrow. Stem cells can be used to create organs, like cloning, that can replace failed or diseased organs in a patient. Stem cells can also be used to research human diseases, as they do not harm living humans, instead of performing those experiments on mice.

Scientists have raised concerns over the dangers of GM food- the mouse on the right was fed GM food

Genetically modified food (GM) is food that has been genetically changed so that it will be resistant to pests, will grow bigger, taller or otherwise be more healthy and more valuable when it is sold. In a way, GM has been happening for thousands of years, as farmers choose the most healthy crops to plant for the next year. GM food is a more technical, and less understood, way of making changes to crops so that farmers can get the most out of their land.

In general, genetic research that is done on humans allows us to see inside ourselves and truly figure out who and what we are. Many people argue that this information can be misused; for example, an insurance company may deny health insurance to someone who has a certain genetic disease that they will only suffer from in 20 years. On the other hand, if we know what diseases we may get, we can start treatment for those diseases before it even becomes an issue.

Questions
Remember
1. What is genetic research?
2. Are stem cells differentiated? How do you know?
3. Why could GM food be bad for you?
Put it together
4. Choose one of the issues and make a one paragraph argument in support of it.
5. Choose one of the issues and make a one paragraph argument against it.
Think about it
6. Food companies want to patent foods that they breed so that they can make money off of selling the seeds. Take the viewpoint of a company that wants to patent a new tomato that doesn't ever go rotten. Write a two paragraph persuasive argument to the Supreme Court of the United States arguing the point.
Review
7. In which cells does mitosis happen?
8. What is a gene?
9. List all of the possible crosses among plants in the F2 generation.
10. How can you avoid mutations that can cause cancer?
Controversy over Genetically Engineered Food

Adapted from an article by Rick Weiss

On a recent day in the English countryside, a handful of people dressed in white decontamination suits trudged to the center of a brilliant green plot of canola plants. Working methodically, knowing the police would soon arrive, the team members cordoned off part of the plot with plastic tape. They opened large bags bearing biohazard symbols and, to the cheering of friends and supporters around the field’s perimeter, began uprooting the lush plants. The plants were engineered by the Monsanto Company, a giant biotechnology firm based in St. Louis, Missouri, to contain a gene from a soil bacterium. That gene protects the plants from a popular weed killer made by Monsanto. Within minutes on that morning in July 1998, more than two dozen constables arrived at the scene. A police helicopter hovered overhead. The protesters were ordered to stop their destructive act. “We can’t,” one explained. “We have work to do.” “Arrest Monsanto!” another exclaimed. “They’re causing criminal damage to other farmers’ crops through genetic pollution!”

The arrests took just 20 minutes, but the group had made its point. Other activists would soon follow in their muddy steps, convinced that a new generation of genetically altered plants being studied on scattered test plots constitute a serious threat to human health and the environment.

Human efforts to modify food crops are not new. In the first 10,000 years or so that people planted and harvested crops, they steadily cultivated hardier varieties by saving and replanting seeds from their best plants. Selective breeding, in use by about 5000 BC, gave farmers another tool to improve their crops. Improvements came slowly but were eventually substantial. The scientific revolution ushered in by the Renaissance encouraged experimentation in selective breeding and quickened the pace of change. Many of the world’s global food staples have changed so much that they would not be recognizable to ancient tillers of the soil.

In the new world of agricultural biotechnology, scientists are no longer constrained by barriers between species. They can take genes from entirely unrelated organisms—viruses, bacteria, even fish and other animals—and splice them directly into plants. In doing so, they are redefining the very nature of the crops upon which humanity has long depended.

Supporters of genetically engineered food have put forward a bold vision for the new agricultural biotechnology. They see a world in which key food crops will be genetically altered to offer better nutrition, repel pests, and flourish in hostile environments—a world in which food is plentiful and hunger scarce. This vision, however, is not universally shared. Some farmers, consumers, environmentalists, and governments have expressed concern that genetically engineered crops pose substantial risks to human health, the environment, and rural economies.

The first genetically engineered field crop to be marketed for human consumption in the United States was the Flavr Savr tomato, which was endowed with genes that delayed ripening. The tomato was approved by the Food and Drug Administration (FDA) in 1994 after years of development by Calgene, a California biotechnology company. The tomato failed commercially, however, in part because of its high retail price. Later that year, Asgrow Seed Company’s virus-resistant squash became the second genetically engineered crop to gain approval in the United States.

Agricultural biotechnology received a major boost in late 1996, when researchers at Monsanto began marketing a new kind of soybean. The soybean was engineered to contain a bacterial gene that allows the soybean plants to withstand the toxins in Monsanto’s popular herbicide, Roundup. Until then, many farmers had relied on hand tilling to control weeds in soybean fields—a tedious, expensive, and time-consuming task. The new variety, known as Roundup Ready soybeans, enabled farmers to spray the weed killer as needed without worrying about killing their crop. The modified soybeans were an instant hit. By 2000 more than 14 million hectares (35 million acres) of Roundup Ready soybeans had been planted in the United States, accounting for more than 55 percent of the nation’s total soybean plantings.

Scientists have also added nutritional genes to crops to increase levels of healthy fats, oils, key vitamins, and other nutrients. In one development with vast medical potential, researchers developed a strain of rice with three extra genes that allow the rice to make beta carotene, which the body converts to vitamin A. Vitamin A deficiency affects 250 million children globally and is the world’s leading cause of blindness.

The agricultural biotechnology revolution is not limited to food crops. Researchers have used gene transfer techniques to make plants that can decontaminate environmental pollutants, such as poisons in the soil around old munitions sites. For example, tobacco plants were given bacteria genes that allowed them to break down TNT, an explosive, into nontoxic byproducts. Researchers have even engineered plants to produce human antibodies or polymer plastics in their cells—advances that could someday revolutionize medicine and industry.

One issue voiced by opponents concerned the possible human health risks of genetically modified food. A 1996 study published in the New England Journal of Medicine, for example, found that a soybean engineered to contain a gene from the Brazil nut to boost the bean’s nutritional value could trigger harmful reactions in people allergic to Brazil nuts. This finding raised the specter of consumers eating potentially life-threatening ingredients in their genetically altered food without knowing about it until it was too late.

Another concern among opponents was that crops engineered for herbicide resistance, such as the Roundup Ready soybean, might create “superweeds” by cross-pollinating with wild, weedy relatives growing nearby. Cross-pollination could give those weeds unprecedented resistance to the very weed killers that farmers were counting on to control pest plants. This type of gene transfer was evident in Canadian canola plants in 1999, when farmers in the province of Saskatchewan discovered that multiple applications of Roundup failed to kill wild canola plants growing along roadsides. Experts continue to disagree about the extent of the problem and the environmental impact. The discovery, however, has served as a potent reminder that herbicide-resistant genes can spread to pest plants.

  1. Identify and define at least six vocabulary terms from the article.
  2. Make a Venn Diagram of 3 pros, 3 cons, and in the middle, a brief summary of what the issue is.
  3. Where do you stand on this issue? Write a two paragraph letter to a member of the government, making sure to reference at least three pieces of evidence from the article in your response.
Scientists Reprogram Human Skin Cells Into Stem Cells

U.S. scientists say they’ve reprogrammed human skin cells into ones with the same blank-slate properties as embryonic stem cells, a breakthrough that could aid in treating many diseases while sidestepping controversy.

Human embryonic stem cells have the ability to become every cell type found in the human body. Being able to create these cells en masse and without using human eggs or embryos could generate a potentially limitless source of immune-compatible cells for tissue engineering and transplantation medicine, said the scientists, from the University of California, Los Angeles.

The researchers genetically altered human skin cells using four regulator genes, according to findings published online in the Feb. 11 edition of the journal Proceedings of the National Academy of the Sciences.

The result produced cells called induced pluripotent stem cells, or iPS cells, that are almost identical to human embryonic stem cells in function and biological structure. The reprogrammed cells also expressed the same genes and could be coaxed into giving rise to the same cell types as human embryonic stem cells, the researchers said.

“Our reprogrammed human skin cells were virtually indistinguishable from human embryonic stem cells,” lead author Kathrin Plath, an assistant professor of biological chemistry and a researcher with the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, said in a prepared statement. “Our findings are an important step towards manipulating differentiated human cells to generate an unlimited supply of patient specific pluripotent stem cells. We are very excited about the potential implications.”

The UCLA findings confirm similar work first reported in late November by researcher Shinya Yamanaka at Kyoto University and James Thompson at the University of Wisconsin. Together, the studies demonstrate that human iPS cells can be easily created by different laboratories and are likely to mark a milestone in stem cell-based regenerative medicine, Plath said.

Reprogramming adult stem cells into embryonic stem cells has significant implications for disease treatment. A patient’s skin cells, for example, could be reprogrammed into embryonic stem cells that could be prodded into becoming beta islet cells to treat diabetes, hematopoetic cells to create a new blood supply for a leukemia patient, or motor neuron cells to treat Parkinson’s disease, the researchers said.

These new techniques to develop stem cells could potentially replace a controversial method to reprogram cells called somatic cell nuclear transfer (SCNT), sometimes referred to as therapeutic cloning. To date, therapeutic cloning has not been successful in humans.

“Reprogramming normal human cells into cells with identical properties to those in embryonic stem cells without SCNT may have important therapeutic ramifications and provide us with another valuable method to develop human stem cell lines,” study first author William Lowry, an assistant professor of molecular, cell and developmental biology, said in a prepared statement. “It is important to remember that our research does not eliminate the need for embryo-based human embryonic stem cell research, but rather provides another avenue of worthwhile investigation.”

However, top stem cell scientists worldwide stress further research comparing reprogrammed cells with stem cells derived from embryos — considered the gold standard — is necessary.

  1. Identify and define at least six vocabulary terms from the article.
  2. Make a Venn Diagram of 3 pros, 3 cons, and in the middle, a brief summary of what the issue is.
  3. Where do you stand on this issue? Write a two paragraph letter to a member of the government, making sure to reference at least three pieces of evidence from the article in your response.
Human Cloning Controversy

Yesterday’s announcement of the successful creation of a human embryo using a cloning technique in the United States has refuelled debate about the regulation of stem cell research.

The technique, undertaken by Advanced Cell Technology (ACT) in Massachusetts, paves the way to produce human embryonic stem cells that exactly match a particular patient, eliminating the risk of an immune response.

Advanced Cell Technology’s research, which is published in the online journal E-biomed: the Journal of Regenerative Medicine, is privately funded. Publicly-funded research into human cloning has been outlawed in America.

But the Australian Academy of Science is supportive of such work, with certain restrictions.

“We do believe this sort of research should be done, but under strictly regulated conditions,” said Professor John White, the Academy’s spokesman on cloning matters.

“We believe that it is a debate that has to be had in public.”

The researchers at Advanced Cell Technology successfully replaced the DNA in a human egg with that removed from the nucleus of an adult skin cell, a process called somatic cell nuclear transfer.

The egg began dividing as if it had been fertilised by a sperm, to become a ball of cells.

“The contentious matter is the use of a human egg and the transfer of human DNA into that egg,” said Professor White. “That is new.”

After several days, the ball of cells grows to a stage at which stem cells can be obtained.

“That’s the stage where there are totally potent cells which can become any cell in the body.”

Advanced Cell Technology has been at pains to point out that their research is for ‘therapeutic cloning’ — that is, for medical purposes — rather than ‘reproductive cloning’, which would aim to develop a new individual.

The distinction between the two is in the treatment of the embryo once somatic nuclear transfer has occurred.

Therapeutic cloning destroys the embryo in the process of deriving stem cells. With reproductive cloning, the embryo would be implanted into a womb for gestation into a baby.

Stem cells can be kept in culture and continually replenished.

“The whole purpose of doing this [research] would be to add to the cell lines that presently exist,” explained Professor White.

“At the moment stem cell lines already exist that are being continued in culture in many countries.”

Stem cells are a type of cell that can be transformed into virtually any of the 200 kinds of cell in the human body. This means that, in theory at least, they can be grown ‘to order’ to help people suffering from degenerative diseases.

In a treatment situation, the DNA from the patient would be injected into a woman’s egg that had had its DNA extracted.

“The egg is grown to the stage where in the blastocyst you could harvest and then grow up in culture, some of those stem cells which would be useful for you personally,” explained Professor White. “That is the hope.”

Stems cells can also be harvested from adults.

“There are many places where stem cells must be present because bone and other tissues regenerate,” said Professor White.

“But whether those cells are totally potent — that is, they can become any other cell — is not in my view proven.”

A House of Representatives report tabled earlier this year in Australia did not support the creation of embryos for experimentation.

Currently, embryos being used for stem cell research are from miscarriages or abortions, or left over from in-vitro fertilization.

But there was an escape clause in the report, said Professor White.

“It didn’t rule out the cell nuclear transfer technique at all, but said it should be held over for three years to see if something else came up in the meantime.”

“I think that things are moving so quickly there may be a case for looking at that three-year moratorium, but that is a matter for discussion.”

  1. Identify and define at least six vocabulary terms from the article.
  2. Make a Venn Diagram of 3 pros, 3 cons, and in the middle, a brief summary of what the issue is.
  3. Where do you stand on this issue? Write a two paragraph letter to a member of the government, making sure to reference at least three pieces of evidence from the article in your response.
OGT Diagnostic Test
Standard & Benchmark Questions Asked Correct Skipped Incorrect
Standard I: Earth and Space Sciences (A) 3
Standard I: Earth and Space Sciences (B) 5
Standard I: Earth and Space Sciences (C) 1
Standard I: Earth and Space Sciences (D) 3
Standard I: Earth and Space Sciences (E) 4
Standard I: Earth and Space Sciences (F) 4
Standard II: Life Sciences (A) 2
Standard II: Life Sciences (B) 2
Standard II: Life Sciences (C) 4
Standard II: Life Sciences (D) 4
Standard II: Life Sciences (H) 3
Standard II: Life Sciences (I) 2
Standard III: Physical Sciences (B) 2
Standard III: Physical Sciences (D) 4
Standard III: Physical Sciences (E) 1
Standard III: Physical Sciences (F) 3
Standard III: Physical Sciences (G) 2
Standard III: Physical Sciences (H) 1
Standard IV: Science and Technology (A, B) 2
Standard V: Scientific Inquiry (A) 2
Standard VI: Scientific Ways of Knowing (A) 1
Standard VI: Scientific Ways of Knowing (B) 1
OGT Review

Daily Routine

1. 10 minutes to rewrite and respond to Extended Response question

2. Trade papers and correct Extended Response question (10 minutes)

3. 1st mini-lecture to big group of students (15 minutes); small group starts on assigned activities and/or vocabulary

4. 2nd mini-lecture to small group of students (if applicable, 15 minutes); big group starts on assigned activities and/or vocabulary

5. Everyone works on assigned activities and/or vocabulary (30 minutes)

6. 5 minutes for exit question based on day’s lesson

Date 1st Period

Mini-Lecture 1

1st Period

Mini-Lecture 2

4th Period

Mini-Lecture 1

4th Period

Mini-Lecture 2

2.28 ES-C

Activity: Oxygen on Earth

PS-A

Topic Skill: Atomic Structure

LS-C (Davante, Chaza)

Test Skills: Diagrams

3.1 ES-A

Topic Skill: Stars

PS-D (Saffo, Tamera)

Topic Skill: Newton’s Laws

PS-B

Topic Skill: Mixtures, Solutions, Acids, Bases

WOK-B (Davante, Antonio, Darnisha)

Topic Skill: Speed, Velocity and Acceleration

3.2 LS-C

Test Skills: Diagrams

LS-E (Saffo, Tamera)

Activity: Adaptive Radiation

ES-A

Topic Skill: Stars

LS-D (Monique, Kassia, Antonio, Conner, Austin)

Activity: Cycles of Matter

3.3 LS-G

Test Skills: Graphs

ES-F (Darnaisa, Justin)

Activity: Finite Resources

ES-C

Activity: Oxygen on Earth

3.4 LS-I

Activity: Natural Selection and Animals

PS-A (Jeremy, Eboni)

Topic Skill: Atomic Structure

LS-A

Article: Interview With a Ribosome

LS-J (Jelanie)

Topic Skill: Relationships and Ecosystems

3.7 PS-E

Test Skills: Units

PS-D (Eboni, Myanna)

Activity: Cycles of Matter

LS-B

Activity: Cell Division

PS-E (Alexis, Jelanie, Jasmine, Darnisha)

Test Skills: Units

ST-B (Bruce)

Test Skills: Graphs

3.8 PS-G

Test Skills: Tables

LS-B (Celestine, Myanna)

Activity: Cell Division

PS-F

Topic Skill: Formation of Energy and Transformations

WOK-C (Keyonna, Austin, Ju’Juan, Bruce, TJ)

Test Skills: Passages

3.9 ES-E

Test Skills: Charts

ES-D (Zebr’e, Chanel, Myanna)

Test Skills: Short Answer

PS-G

Test Skills: Tables

PS-D (Davante, Jelanie)

Topic Skill: Newton’s Laws

3.10 ES-B

Article: Rocks Tell Tale of Early Warm Atmosphere

LS-F (Marcus, Isolene, Jerome, Robert)

Test Skills: Extended Response

LS-E

Activity: Adaptive Radiation

ES-B (Davante, Kassia, TJ, Jasmine)

Article: Rocks Tell Tale of Early Warm Atmosphere

3.11 LS-A

Article: Interview With a Ribosome

LS-J (Jeremy, Yvette, Myanna, Justin)

Topic Skill: Relationships and Ecosystems

LS-I

Activity: Natural Selection and Animals

PS-C (Davante, TJ, Jasmine)

Test Skills: Experiments

Directions for Activities

– For “Test Skills” sheets, write down the most important tip on the inside cover of your folder

– Complete the activity.  Get an answer sheet from me.  Correct your answers and hand back the answer sheet.

– For “Topic Skills” sheets and other activities, write down the most important fact that you learned on the inside cover of your folder.

Directions for Vocabulary

– Get a blank vocabulary sheet and take one set of your assigned words.  Complete the vocabulary sheet.

– Place the vocabulary sheet back in your folder.

Science Fair
Projects: Week Two

1st Period, Anatomy & Physiology: http://shawmst.org/thebody/

Programming: http://shawhighstudents.org/webdesign/

  • Finish “Lesson 3: Structure of the Internet”
  • Start “Lesson 5: HTTP, Client vs. Server”, “Lesson 8: What is Design?”, “Lesson 9: Your First Page”

Environmental Science: http://shawmst.org/biology/ ; http://shawhighstudents.org/apes/

Gardening: http://shawmst.org/biology/ ; http://shawhighstudents.org/apes/

Projects: Week Three
Projects: Week Five
Test Activity
Snakes and Rabbits

In Forest Hills, there are snakes and rabbits (among other animals). For each snake to survive a year, they need to eat three rabbits. However, since rabbits reproduce quickly, each rabbit produces three new rabbits every year. Snakes don’t reproduce as quickly, each one only producing one new snake per year. You are going to find out what happens to the rabbit and snake populations of Forest Hills over the course of 10 years, starting in 2011.

  1. To start off your populations, take the number of the month that you were born (January = 1, February = 2, March = 3, etc.) and multiply it by 10. Write that down here: _____
  2. Add to the number from #1 the day of the month that you were born. Write that sum here: _____
  3. This number is the number of snakes in 2011. Enter it into the table below for Column A in 2011.
  4. Now, multiply the number of snakes by 12 to get the number of rabbits in 2011. Write that product here: ___
  5. Enter your answer from #4 into the table below for Column B in 2011.

Due to the size of Forest Hills, if the number of snakes goes above 100, then there is not enough space in the ecosystem for the snakes. They die off in huge numbers, and there will only be 10 surviving snakes. If the number of rabbits goes over 1,000, then there is not enough food or space for the rabbits. They die off in huge numbers, so there will only be 100 surviving rabbits.

Year A# of Snakes B# of Rabbits CSurviving Snakes DRabbits

killed

ESurviving Rabbits FNew rabbits produced
Column C (previous year)multiplied by 2 Column E (previous year)+ Column F (previous year) This is equal to Column A unless A is over 100; then this is 10 Column Cmultiplied by 3 Column B- Column D

If this is over 1,000 then it drops to 100

Column Emultiplied by 3
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020

Now create a graph for Columns A and E. Use one color for Column A, and another for Column E.


Miller & Levine Biology Book

Do the review questions listed. Make sure all questions are correct for full credit. You can always read the book so that you can get all of the information that you need!

Ethics
  1. Read about one of the genetic ethical controversies 
  2. Make a Venn Diagram of 3 pros, 3 cons, and in the middle, a brief summary of what the issue is.
  3. Get in a group of three, where each one of you has a different issue.
  4. In turn, every group member should explain their issue to everyone else, without stating their own opinion. Make sure to give pros and cons!
  5. On two pieces of construction paper taped together (on the short side) draw three lines going across. Label each one a different genetic ethical controversy. Label one side of the lines “AGREE” and one side of the lines “DISAGREE”.
  6. For each issue, determine where you stand. Then, sign your name where you feel you stand on each issue.
Transcription & Translation

Background

As we know, DNA is in the nucleus of a cell. The ribosomes that make proteins from the DNA’s instructions are located outside the nucleus of the cell. So how do the genetic instructions get outside of the nucleus?

Transcription

DNA has two halves, as we have already seen. The two halves (strands) separate from each other, then a copy of one half gets made. This copy is messenger RNA, or mRNA. This mRNA can then leave the nucleus.

Translation

The mRNA then goes to a ribosome. The ribosome is made up of two halves, which open and then close on the strand of mRNA. The ribosome then reads the mRNA, pulling it through the two halves. Every time it finds a codon, it then calls a tRNA. That tRNA has an amino acid attached to it. By pulling in multiple tRNAs, the ribosome assembles a protein.

Activity

Draw and label with descriptive captions the following steps of how DNA becomes a protein in a Four Door foldable. The four doors should contain:

  1. A gene of DNA is transcribed into mRNA
  2. mRNA leaves the nucleus
  3. Ribosomes translate the mRNA, adding amino acids
  4. The amino acids form a protein

Translation

Transcription

Sex-Linked Traits

From Kihei Charter STEM Academy

Background:

Sex-linked traits are those whose genes are found on the X chromosome but not on the Y chromosome. In humans the X chromosomes are much larger than the Y chromosome and contains thousands of more genes than the Y chromosome. For each of the genes that are exclusively on the X chromosomes, females, who are XX, would obviously have two alleles. Males, who are XY, would have only one allele. Thus females with one recessive allele and one dominant allele, for a gene that is unique to the X chromosome, will always display the dominant phenotype. However, a male with a recessive allele for a gene unique to the X chromosome will always exhibit that recessive trait because there is no other corresponding allele on the Y chromosome.

In humans, each of two different sex-linked genes has a defective recessive allele that causes a disease. The diseases are hemophilia and colorblindness. In hemophilia, the defective allele prevents the synthesis of a factor needed for blood clotting. In colorblindness, the defective allele prevents a person from seeing certain colors.

Use the information below to answer the following questions.

XH - X chromosome with normal dominant allele (no hemophilia)
Xh - X chromosome with recessive hemophilia allele
Y  - Y chromosome (does not contain gene)
XB - X chromosome with normal dominant allele (not colorblind)
Xb - X chromosome with recessive colorblind allele
Y  - Y chromosome (does not contain gene)
  1. Write the genotypes for the following phenotypes of red-green color blindness.
    1. normal male
    2. normal female carrying no colorblind alleles (Homozygous)
    3. colorblind male
    4. normal female carrying the colorblind allele (Heterozygous)
    5. colorblind female
  2. Complete a Punnett’s Square between XBXB x XbY.
    1. What proportion/percent of the male children are colorblind?
    2. What proportion/percent of the female children are colorblind?
  3. Complete a Punnett’s Square between XBXb x XBY.
    1. What proportion of the male children are colorblind?
    2. What proportion of the female children are colorblind?
  4. What is the probability that a colorblind woman who marries a man with normal vision will have a colorblind child? Show the Punnett’s Square.
  5. A normal-sighted woman (whose father was colorblind) marries a colorblind man. Show the Punnett’s Square.
    1. What is the probability that they will have a son who is colorblind?
    2. What is the probability that they will have a colorblind daughter?
  6. For the following Sex-Linked Punnett’s Squares:
    H = normal blood clotting
    h = hemophilia

    Show the Punnett’s Square between XHXh x XHY. What is the probability that any of their offspring will have hemophilia?

  7. A woman who is a carrier for hemophilia marries a hemophiliac man. Show the Punnett’s Square.
    1. What proportion of the male children are hemophiliacs?
    2. What proportion of the female children are hemophiliacs?
  8. A phenotypically normal man marries a homozygous normal woman. Show the Punnett’s Square. What is the probability that any of their children will be hemophiliacs?
  9. A phenotypically normal woman has phenotypically normal parents. However, she has a hemophiliac brother (Mom is carrier).
    1. What is mom’s genotype?
    2. What is dad’s genotype?
    3. What is the brother’s genotype?
    4. Show the Punnett’s Square.
    5. What are her chances of being a carrier for hemophilia?
  10. Answer the following questions using your knowledge of sex-linked traits and the background information.
    1. What is a sex-linked trait?
    2. Why must males inherit colorblindness or hemophilia from their mothers?
    3. Why is colorblindness or hemophilia more common in males than in females?