Huntington's: An Overview

Huntington's Disease (HD) is an autosomal genetic disorder that results in the deterioration of the nervous system. It doesn't usually present symptoms until the person is in their 30s-40s.
Because HD is a dominant trait, there are no carriers. Thus, is a child is tested and found to have HD, then one of the parents must have it (even if they don't know it yet)
Symptoms include "uncontrolled movements, loss of intellectual faculties, and emotional disturbance"(1) once HD presents itself. Early symptoms may include "mood swings, depression, irritability or trouble driving, learning new things, remembering a fact, or making a decision" (1).

Each child of a parent with HD has a 50-50 chance of getting the disease. Because Huntington's presents itself later in life, many people already made the decision to have children. If they did not know one of their parents, it would problematic because they they don't know what they may pass on.

Testing for Huntington's became available in 1993, however, there is no cure or treatment for it (2). HD develops in almost 100% of people who have the mutation. (6) The best we can do it to treat the symptoms of the disease.

HD is surprisingly common. More than 250,000 Americans are at risk, which means that a parent had the gene. HD affects as many people as Hemophilia, Cystic Fibrosis or muscular dystrophy (2).

Most at-risk individuals do not decide to test for the mutation. The 'prospect of finding out that one has an untreatable lethal mutation and having to decide whom then to tell are simply to frightening" (5)




"rendering of a broken DNA helix... Researchers recently uncovered evidence that faulty DNA repair may be to blame for the onset of Huntington's disease symptoms." (7)

The Argument: Pro

The problem with screening for Huntington's disease is lies in revealing a child with HD. By doing so, you are also revealing that one of the parents must have HD. Is this a violation of privacy of the parent? It has become a conflict between the rights of a parent and the rights of a child. Should the parents have the ability to screen their child for HD if they know it's in the family history? Or should the child be able to make the decision when she or he's 18? Even if they were allowed to, however, they would know they had a chance of having HD because their parents would be revealed as having HD in the meantime. Should that make a difference? Should the parents have the ability to keep the test results from the child? If there is a couple, and the mother wants her fetus tested for HD, but the father doesn't want to know if he has HD? Should the mother be able to make the decision? Or should the father's argument prevail? The questions of ethics arises. Here are some arguments in FAVOR or screening an infant for HD.


-By screening infants for HD, you are giving the parents the chance to prepare themselves or their child for lives with HD.

-By screening infants for HD, you are preventing further cases of HD from spreading. If each child grows up knowing they have HD, they will be able to make a fully formed decision about having children. As most people have children before their 30s, and they may not know their parents medical history, they can decide whether or not they want to subject their children to the possible dangers.

-One man was convinced he had HD and decide not to have children. He took up dangerous sports, like skydiving and cliff-jumping. If he had been screened for the disease, he would have found that he didn't have the mutation. (6)

-By screening a child for HD, you are giving the family the chance to be ready to treat early symptoms. Not to mention that the family may be able to participate in drug trials or experimental medicine.

-By not informing a child about their HD, they will face huge, traumatic, and life-changing events when they do find out. Any long-term dreams they have will be hopeless. If they grow up knowing they have HD, then they will be prepared to deal with HD as an adult.

-If we start screening all infants for HD, the problem soon won't be a problem. If anyone at-risk knew they had HD, then testing the infant wouldn't be a problem because the parent would already know if the had HD or not. However, this would not solve the problem of whether or not it is important to wait until the child turns 18.

The Argument: Con

Here is a sample of the arguments against screening infants for Huntington's disease. I won't post all of them up here (wouldn't want to give the other side too much of an advantage!)

-By not screening infants for HD, you are allowing the child to make the decision when they're 18. Because HD doesn't usually present itself until 30s-40s/50s, then the child is given plenty of time to make their own choice
~~~~~Pro Counter Attack: If an infant is not screened for HD and it is left up to them for when they turn 18, then they will see their parents suffer from it in the meantime. They will know they have a 50/50 chance of having HD. How would you feel if you were a potential, ticking time-bomb? They may assume the worst and act out rashly.

-The rights of the parents come first. If they don't want to know, then they shouldn't have to.
~~~~~~Pro counter attack: They should have thought of that first. Because they didn't get themselves screened in the first place, they are now inflicting the decision on someone else.

Post-Debate Reflection

It was really a very civilized debate.


I debated with Mr. Cornelius Chavis. He had a lot of good points.

We discussed the screening of infants with Huntington's disease. He was arguing against it and I was arguing for it. The debate opened with us presenting our sides; I started and went over my three minutes (and my 30 second grace period; whoops). Then Cornelius presented his points. Some of them are listed above, but he also brought several more points to my attention. The first one was that anyone who was tested and knew they were positive may become suicidal. I countered this by citing an article (Bioethics for the Future) that stated that people who tended not to be bale to handle the results would not go for the testing and that the suicide rate was lower than expected. He other thing he pointed out was that by diagnosing an infant, you can also diagnose an adult. If that adult did not want to know, then it would be a violation of those rights. I responded that, if the adult had been tested in the first place, it would not be an issue. Not to mention the fact that he would have been able to make an informed decision about whether or not he wanted to have children if they had a 50/50 chance of having Huntington's disease. Another case I chose to bring up to support this was one in which my mom had seen. She had traveled to Florida to stay with my aunt in a Cancer Treatment Center and there was a young woman there who had cancerous tumors. It turned out they were genetic. One of the toughest things she had to cope with was the fact that she may have passed it onto her son without knowing it.

Sources/Bibliography

1. http://www.ninds.nih.gov/disorders/huntington/huntington.htm
2. http://www.hdsa.org/about/our-mission/what-is-hd.html
3. Terrenoire, Gwen. Journal of Medical Ethics. Huntington's Disease and the ethics of genetic prediction. 1992.
4. http://www.scu.edu/ethics/publications/iie/v9n2/outstrips.html
5. http://virtualmentor.ama-assn.org/2009/09/ccas2-0909.html
6. Bioethics: Choices for the Future. When Diagnosing a Fetus Also Diagnoses a Parent: Huntington's Disease.
7. http://www.sciencedaily.com/releases/2007/04/070422141755.htm

Part II: Design a Species

1. TRAITS (phenotypes and genotypes)







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2. THE CREATURES

Frederick Wilhelm III




The possible genotypes (given that he is male):
ee = Green eyes
AA or Aa = Green legs and arms
rr = no spots
TT = Buck teeth
FF = Eyebrows arched down
JJ = Tin foil hair
X(n)Y = Male, pointed nose

As you can see, I gave him an example genotype on the card beside him.





Lawrence Wigbert Jr.



The possible genotypes (given that he is male):
Ee or EE = blue eyes
aa = red arms and legs
RR or Rr = red body spots
Tt = single tooth
Ff = one eyebrow arched up and one arched down
HH = cotton ball hair
X(N)Y = male, button nose

As you can see, I also gave him a example genotype on the card beside him.

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3. PEDIGREE
Here, I created a sample pedigree with a key for the eye color of the creatures:

Key:


Pedigree:

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4. DIHYBRID CROSS



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5. PRACTICE PROBLEMS

1. What would the creature with the genotype EeAARRttFfLHX(n)X(n) look like?

2. Cross a a homozygous blue-eyed creature with a heterozygous blue-eyed creature. Then cross the the F1 generation. What are the ratios for each cross? In the F1 generation, are there any green eyed-creatures?

3. What is the purpose of crossing a homozygous green eyed creature (recessive) with an blue creature with an unknown genotype? Is there a word for this?

4. What would an a creature with this genotype look like? eeaarrTtffHHX(N)X(n)


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6. Pictures
See answers above. Pictures are in the 1st question, along with the possible genotypes and descriptions of the displayed traits.

Part III: Creature DNA Fingerprinting

Who could have blasphemed the Easter Bunny?

Could it be Lawrence? Or Frederick? *Dun dun dun...*


We must prove them innocent! Here is a sample of their complemetary DNA sequence that cleaves in 3 spots:




Will it match with the crime scene DNA in gel electrophoresis?