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13 Apr 2018

Ch. 10 Case Study: Hospital Tests Babies Al and Victoria are in their early 30s and had been married for 5 years when their first child was born. Victoriaâs pregnancy was perfectly normal, and she had continued working until one week before the babyâs birth. She had never felt better. At birth, Al and Victoriaâs son appeared perfectly normal. A few days after they took the baby home, the doctor called to say that the baby needed more tests. He asked that both parents come to them office visit because he wanted to talk to them. In his office the doctor said that a blood test done in the hospital showed that their child had a genetic disorder called phenylketonuria (PKU). If their child was not treated using a special diet, he would become mentally retarded. Al and Victoria had never heard of PKU and this news upset them. They immediately called around to family members and found that only a few relatives on either side of the family had ever heard of PKU, and none knew of any family member with the disorder. Al and Victoria wondered how a genetic disease that no one in their family had could suddenly appear in their child. They made an appointment for another visit with the doctor, and in the meantime began reading about PKU. 1. Why was Al and Victoriaâs baby tested for PKU in the first place? 2. Neither Al nor Victoriaâs family has a history of PKU. Should Al and Victoriaâs baby have been tested at all? Explain. 3. Should Al and Victoria have the right to refuse this testing for their child? Why or why not? 4. PKU is a treatable genetic disorder. Affected children must follow a strict diet that prevents many of the conditionâs symptoms. Does this information change your opinion about testing the baby? 5. Testing newborn for PKU is done in every US state; some states offer more extensive testing for newborns. Al and Victoria live in one of these states. Should they have been notified of the testing? Why or why not?

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15 Apr 2018

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Genetics question on genetic dwarfism:

Seven months pregnant, an expectant mother was undergoing a routine ultrasound. While prior tests had been normal, this one showed that the limbs of the fetus were unusually short. The doctor suspected that the baby might have a genetic form of dwarfism called achondroplasia. He told her that the disorder was due to an autosomal dominant mutation and occurred with a frequency of about 1 in 25,000 births. The expectant mother had studied genetics in college and immediately raised several questions. How would you answer them?

1. How could her baby have a dominantly inherited disorder if there was no history of this condition on either side of the family?

2. Is the mutation more likely to have come from the mother or the father?

3. If this child has achondroplasia, is there an increased chance that their next child would also have this disorder?

4. Could this disorder have been caused by X rays or ultrasounds she had earlier in pregnancy?

Thank you!

ultramarinemule185

read the article. and video

https://www.youtube.com/watch?v=MW3ugmGt-9s

By referencing the textbook reading and the video; audio, answer the following questions:

1) Define karyotype.

2) Define Down Syndrome.

3) Describe the challenges addressed in the Perfect video. Compare and contrast to the Herzenberg family.

Only Human is a new podcast from WNYC Studios. Hosted by Mary Harris, Only Human tells stories we all can relate to. Because every body has a story. Subscribe to Only Human on iTunes or wherever you like to get your podcasts.

When Lee Herzenberg remembers the day her son Michael was born, she laughs and calls it a "cool birth." Her obstetrician was a friend, and she describes it almost like a party â "a little bit painful, but that you forget very quickly." Lee even got a kick out of the fact that a resident learned to do an episiotomy on her.

It was November 1961, and she was at the newly christened Palo Alto-Stanford Hospital Center; her husband, Len, was a biology professor on campus. Like most fathers at the time, he didn't attend the birth, which meant he wasn't there when Michael started turning blue.

The nurses whisked the newborn off to the nursery without telling Lee anything was wrong.

It was then that a doctor noticed the characteristic features of Down syndrome: floppy muscles, eyes that slanted upward. They got Michael breathing again, but doctors thought his prognosis was grim. They gave Michael just a few months to live. A daisy chain of physicians was called, and Lee says it was a pediatrics professor who told her husband what had happened. Then Len was dispatched to tell Lee.

She remembers the moment with uncharacteristic emotion. "We hugged each other, and it was a terrible conversation to realize that you'd lost the baby, but the baby was lost," Lee says now. "We knew immediately what we'd do. We had already made the decision that it was not a good thing to take the baby home, and so we didn't."

In the 1960s â an era before neurodiversity movements and early intervention programs â many people still called people with Down syndrome "mongoloids." Playwright Arthur Miller institutionalized his son, Daniel, in 1966. A few years later, an article in The Atlantic Monthly argued that "a Down's is not a person."

Lee and Len Herzenberg had seen friends struggle with the birth of a child with Down syndrome and had even gone with a colleague to an institution, where he dropped off his own infant daughter.

So, they decided Michael would never come home.

But Michael wasn't absolutely lost to them. Michael's birth sparked their search for a blood test that has revolutionized prenatal care in this country.

I made the mistake of telling one scientist I was reporting about "Len Herzenberg's lab." He corrected me instantly: "Len and Lee's lab." Because Lee Herzenberg was "leaning in" decades before Sheryl Sandberg coined the phrase. At 81, Lee, a professor of genetics, is still running the lab she and her husband founded more than 50 years ago. Len died in 2013.

The lab is a quirky place, even by Stanford standards. Lee rarely sits on chairs, preferring cushions on the floor. She's often accompanied by her bichon frise, Gigi. Researchers can often be found working in this basement office well into the night.

But Lee Herzenberg isn't just quirky. She is one of the few professors at Stanford â possibly the only one â never to have officially graduated from college. Instead, she trained by her husband's side, auditing courses while he got his Ph.D. at Caltech (women weren't allowed to attend at the time) and working at his labs at the Pasteur Institute in Paris and the National Institutes of Health.

And the science that's been done here has changed the course of medicine.

The Herzenbergs are best known as the creators of the modern-day fluorescence-activated flow cytometer, or FACS. It was a machine born out of frustration: Len couldn't stand squinting down a microscope looking at cells.

Before the FACS, a biologist peering at slides could feel like he was playing a really intense round of "Where's Waldo," staring at crowds of all kinds of cells, trying to pinpoint the exact ones he was looking for. Not only was it annoying â Len Herzenberg worried it wasn't particularly scientific. He wanted a way to find and describe cells that didn't rely on his worn-out eyes.

The FACS allows you to pour cells in, program the machine to find whatever it is you're looking for, and then it will spit out a little tube of just those cells alone. And the FACS gives you all kinds of information, too: how big the cells are and how much DNA they have inside.

The FACS was used to diagnose AIDS because the technology can quickly and easily sort out T cells. The FACS was used to find the first stem cells. When Len Herzenberg died, one colleague told The New York Times that "without Len, tens of thousands of people now alive would not be."

But in the 1970s, the Herzenbergs were still proving the value of this machine. That's when they started thinking about using it to create a blood test for Down syndrome.

Len had seen research from Finland claiming it was possible to see a fetus's cells in a mother's blood. It was hard to believe. But he figured that FACS, with its nearly magical sorting capabilities, could figure it out. So he took on a medical student named Diana Bianchi as a research associate and made sorting out these cells her project.

If they could isolate these cells, he could learn a lot about the developing fetus, including whether the fetus had chromosomal abnormalities.

"They had a very personal reason for doing this, because of their son Michael," Bianchi says now. "They wanted to have a test that could be offered to any pregnant woman â that would be noninvasive and would allow them to know if a child had Down syndrome. The first step, however, was to show that you could pull out fetal cells."

Scientists now estimate that for every 200 billion cells in a mother's bloodstream, about 10 of those are fetal cells. Bianchi was one of the first people to see them.

The New York Times quoted Len saying the work was a "first step" toward a blood test for Down syndrome for all pregnant women. But it would take 30 years for a practical test to become a reality.

As it turned out, Len's FACS wasn't the right tool for prenatal diagnosis. There weren't very many fetal cells to be sorted, and if a pregnant woman already had children, scientists couldn't be sure if the cells in her blood came from the current fetus or one of her older kids.

But in 2008, Len helped ensure the right tool was found.

A researcher named Stephen Quake had discovered a way to sequence chunks of fetal DNA floating in expectant mothers' blood. As a member of the National Academy of Sciences, Len made sure the paper was published in the academy's journal. Another researcher, Dennis Lo, confirmed Quake's findings. Three years later, the tests were on the market.

Now, at just 10 weeks into a pregnancy, a whole range of things can be revealed with this test. Not just Down syndrome, but a host of other chromosomal abnormalities as well as the sex of the child to be.

Until this test, doctors had to rely on amniocentesis, an invasive procedure that involves inserting a needle in the womb to sample amniotic fluid, or biopsying the placenta, to tell them with any reliability whether a fetus had a chromosomal abnormality. These tests aren't just uncomfortable; they come with a risk of miscarriage. By some estimates, in the past five years the number of these procedures performed in this country has plummeted by more than 50 percent.

To some parents, this knowledge can be alarming. Advocates in Ohio are trying to pass a law preventing abortions if Down syndrome is the reason (North Dakota and Indianahave already passed similar laws).

Lee Herzenberg is honest about what she would have done if she'd known early on in her pregnancy that Michael had Down syndrome.

"I'd say if I had the choice of not pushing Michael into this life â if I at that time would know I was carrying a Down syndrome child â I would have aborted the child," she says. "I see no reason Michael has to live the life he leads. The fact that we've made it very happy for him or that he's made it very happy for us â all of that is adapting to a situation, but I don't think it's fair or proper."

But Lee is alarmed that these tests are now being used to determine the sex of unborn babies. She worries about parents choosing to abort girls.

Diana Bianchi, that medical student from the Herzenberg lab, is now a professor at Tufts, where she founded the Mother Infant Research Institute. She's still working in prenatal testing. In fact, perfecting these tests has become her life's work.

But her focus has shifted. Now that she can detect Down syndrome so early, she wants to treat it early, too â in the womb. Because finding this chromosomal abnormality at 10 weeks means there's a window of opportunity: The brain changes associated with Down syndrome don't occur until a month or so later. Theoretically, you could treat a fetus before some brain changes occur at all.

Bianchi's work is still early. She's experimenting with mice, giving them existing drugs in utero to see if she can forestall brain damage.

There's an often-quoted statistic, that 90 percent of parents who find out that their fetus has Down syndrome will abort. But that statistic is from a study done in the United Kingdom. In the U.S., far fewer women terminate.

"We have to unpack this connection between prenatal testing and abortion," she says. "We have good data to suggest that approximately 40 plus percent of women who know their fetus has Down syndrome continue their pregnancy. There are many women who speak very highly of the fact that this allows them to prepare."

The Down syndrome baby who kicked off the search for this blood test is now a 54-year-old man. He lives in a squat house in Redwood City, Calif., just a 30-minute drive from his birth mother's home.

For years, Michael lived with a local woman named Barbara Jennings, who raised a number of children with developmental challenges. The Herzenbergs' pediatrician helped them find her when Michael was a newborn. The Herzenbergs would visit Michael every month or so, but they never felt they should bring him home. When Barbara died, Michael moved to this group home.

It's hard to know how much Michael understands when I speak to him, though he has learned to read and use a cellphone. And he's stubborn. A lot like his mother, actually. "Michael has the hardest head in the whole world," says Janet Thomas, the caretaker who runs this house. "He does whatever he wants to do. He does not care whatever you say. He's going to do whatever it is he wants to do â that's Michael."

I asked Lee if she ever regretted not raising Michael, and she said no. "It was a decision that was selfish, if you like, because we had things we wanted to do. In retrospect, a lot of things would never have gotten done. There would be no FACS had we decided to do this. Because it would have been a very intensive kind of upbringing."

As for Michael, he clearly loves his mother, no matter what she decided. In Michael's room, there are photos on almost every surface, with snapshots of his biological and adopted families. In the corner is a huge poster of his father, celebrating when he won the Kyoto Prize for his contributions to biotechnology. And deep in one album, there's a picture of Len and Lee together. The caption reads: "Michael's Other Mom + Dad."

pearswan961

Roger Maxwell is very health-conscious. He runs, swims, and hikes; follows a lowcarbohydrate diet; and generally feels great. He sees a physician when he needs to, in addition to annual physical exams at the large company where he is an engineer. He'd never allow himself to get so out of shape that heart disease would be a risk. Because of his strict adherence to this healthy lifestyle, Roger is surprised when a medical intern, gazing at his yearly elecfrocardiogram (ECG) at his work physical, clearly picks up on something.

"What? What are you looking at?" Roger blurts out while buttoning up his shirt.

"Oh, it's probably nothing." But she doesn't look like it's probably nothing.

"The heart murmur? My mom's been telling me about it since childhood. Not a big deal. The doctors called it something last year, something I never heard of." "Did you check it out?" asks the intern.

"Nah. It wasn't bothering me, so I forgot about it. Why? What's wrong?"

"Well, maybe you should ask the doctor to explain it again and suggest what to do."

"About what?"

"The doctor will explain it. Please don't worry, though," says the intern as she rushes off to the next patient.

Roger's electrocardiograms had in fact been showing that he has had long QT syndrome, and not a heart murmur, for many years. The doctor explains that this is a problem with the heart's rhythm, and not its valves. Roger goes home and Googles long QT syndrome right away. What he finds concerns him enough to alert his relatives.

Long QT syndrome is a lengthening in the time that it takes the ventricles (the lower two heart chambers) to recover after a contraction, called the QT interval on an electrocardiogram. This delay is called torsade de pointes, and it causes lightheadedness upon standing or even fainting, as blood pressure drops when the heart rhythm becomes abnormal. If the arrhythmia turns into the more erratic condition called ventricular fibrillation, it can be deadly. Some cases â¢of sudden cardiac arrest in people who apparently do not have heart disease are in fact due to long QT syndrome. This 'may have been the case with Roger's aunt, Amelia, his mother's sister, who died at age 34 of what was thought to be a heart attack, but, now Roger realizes, was more likely an arrhythmia. Still, with only one affected relative, Roger had never thought of his aunt's â¢early demise as a family history, especially since his mother is healthy.

Roger reads that in people with some forms of long QT syndrome, fatal arrhythmia can be triggered by intense emotions or a sudden loud sound. The first recorded case of the condition was a little girl, who collapsed dead â¢when her teacher suddenly yelled at her. Her older brother had died in a similar circumstance. Suddenly, Roger remembers that his daughter Sheila faints very easily. She even passed out once at a rock concert because she got so excited. He'd never panicked over it because his mother fainted easily, too. A pattern was emerging.

Long QT syndrome is caused by mutations in any of at least 10 genes that encode either proteins that form parts of ion channels (potassium, sodium, or calcium) or proteins that affect the functioning of these channels. Ion channels control the spread of nerve impulses and the resulting muscle contraction. The time for the heart's reeovery after a beat, called repolarization, extends the period when ions are trapped inside heart muscle cells because the channels are blocked, too slow to open, or too quick to close in people who are at elevated risk due to inheriting a mutation. People with long QT syndrome can experience arrhythmia if they take certain drugs that prolong the QT interval. These drugs include certain antibiotics, antidepressants, and diuretics ("water pills").

Roger reads about the different genes and drug combinations that cause long QT syndrome on Wikipedia, and then he scans www.genetests.org to find labs that test for all of them. Only then does he make an appointment with a cardiologist, and he arranges to have his blood and that of his daughter and mother sent to one of the labs. Two weeks later, he learns that they all have a dominant mutation in a gene called HERG (for "human ether-a-go-go") that causes long QT syndrome type 2 (LQT2). Even healthy family members could have inherited the mutation, because 15 percent of people with long QT syndrome do not have symptoms. The concern is their increased risk of developing symptoms in the futureâperhaps suddenly.

Question 1 : Roger is upset that in the past doctors had not been more insistent that he follow up on the abnormal ECG pattern. When he mentions this to his primary care physician, she answers, "I didn't say anything because you are so healthy, and people who have cardiac arrest from long QT do so in young adulthood. You're too old to worry about it." But Roger should be worried, because

a. he looks younger than he is, so could still be at risk

b. the condition can be inherited, so others in the family could be affected.

c. he could die at any time.

d. he can no longer take antibiotics.

e. long QT syndrome can cause cholesterol to build up in his coronary arteries.

2. Individuals who should take genetic tests for long QT syndrome are

a. all the people in generation IV.

b. Eric, Joan and Peter, and then Dylan, Anika, Sean, Keri, and Anna if a parent has the mutation.

c. Juanita, Larry, Joan, Peter, and Ellie.

d. Abe, Sara, Craig, Philip, Edwin, and Yvonne.

e. Only those who are athletic.

3. The mode of inheritance of long QT syndrome in the Maxwell family is

a. X-Iinked recessive

.b. autosomal recessive.

c. autosomal dominant.

d. sex-limited.

e. X-Iinked dominant.

4. Some people who inherit the same mutation as Roger do not experience any symptoms. This means that the mutation is

a. variably expressive.

b. genetically heterogeneic.

c. polygenic.

d. incompletely penetrant.

e. dominant.

5). The fact that mutations in any of several genes can cause long QT syndrome means that the condition is

a. variably expressive.

b. genetically heterogeneic.

c. polygenic.

d. incompletely penetrant.

e.recessive.

6). The risk that Sean, Keri, or Anna has inherited the family's mutation for long QT syndrome is

a. 1

b. Â¾

c. Â¼

d. Â¼

e. 1/8

7) Roger is relieved that he does not have- LQT7, which affects skeletal as well as cardiac muscle, causing short stature and scoliosis. He is also glad that he doesn't have LQT8, which causes many symptoms, or either of two types that also cause deafness. These other forms of the condition, with more than one symptom, exhibit

a. invariable expressivity.

b. complete penefrance.

c. genetic homogeneity.

d. pleiotropy.

e. phenocopy.

8) The reason that mutations in different genes all cause the same phenotype of extended QT interval on an ECG is that

a. the heart is an extremely complex organ.

b. the genes all encode proteins that affect ion channels essential for maintaining heartbeat.

c. the genes all encode the same protein.

d. the mutations all affect the genes in the same way.

e. the QT interval is highly variable, even within individuals at different times.

9). A phenotypic pattern in a family that could be due to inherited long QT syndrome is

a. sudden cardiac death in one or more young people and individuals who faint easily.

b. many individuals who eat a very fatty diet and are sedentary but do not develop heart disease.

c. many individuals with hypertension.

d. many individuals who suffer heart attacks after age 50.

e. a family with rnany athletes who have very low heart rates because of intense and frequent exercise.

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