Exam 3 Flashcards
What is applied genetics in prenatal medicine used for?
The goal is to detect, and hopefully cure (well, at least treat), certain kinds of genetic diseases.
How are genetic diseases developed?
Human development from fertilized egg to new-born baby can go wrong for many reasons, including environmental insults (e.g., alcohol abuse during pregnancy giving rise to fetal alcohol syndrome) or genes (perhaps inherited from one or both parents) that do not function properly.
What is ultrasonography used for in prenatal medicine?
Ultrasonography can detect large-scale anatomical problems. But what about more subtle problems, such as disorders of chromosome numbers or biochemistry?
How can one detect certain genetic abnormalities?
Amniocentesis and chorionic villus sampling (let’s just call the latter CVS) can be used to detect certain genetic abnormalities, by looking at chromosomes and genes, or by looking at gene products (proteins). An extra copy of chromosome 21 might be detected. Such trisomy results in a disorder known as Down syndrome.
What are genetic counselors?
Genetic counselors advise people with known genetic diseases on the odds of having children that may be affected – they are experts in the understanding of patterns of inheritance for such diseases. With that advice, affected couples can then make informed decisions about whether they wish to become biological parents.
What is a way to detect subtle problems in pregnancy even before Amniocentesis and CVS?
Amniocentesis and CVS can detect subtle problems fairly early in pregnancy, but the technique of pre-implantation genetic diagnosis (or PGD) allows detection of problems even before a very young embryo implants into its mother’s womb.
In PGD, cells from very young embryos produced by in vitro fertilization are screened for chromosomal abnormalities and defective genes. Only those embryos whose cells reveal normal chromosomes and genes are then put into their mothers’ wombs.
What is the most recent tool developed for prenatal diagnosis?
We’ve fairly recently developed another tool for prenatal diagnosis. Believe it or not, DNA from a fetus can be found in a pregnant woman’s blood. We can isolate that fetal DNA, make copies (by PCR) and sequence it to see if it is normal. This is a very low-risk procedure because all it involves is taking some of Mom’s blood.
What is applied genetics in gene therapy used for?
The goal is to replace a defective gene with a functional copy, and so cure – well, at least treat – a genetic disease. But, would the offspring of such a cured individual be guaranteed a disease-free life? Not necessarily, but do you know why?
How do we edit genes using CRISP-Cas9?
Gene editing using CRISP-Cas9 will revolutionize gene therapy in the (not so distant?) future. But right now it isn’t in clinical use. Here’s how we do it now…
Remember our ISICU strategy? First, Isolate a functional gene, then Copy it and finally Use it by putting it into an affected person.
Fatty blobs (liposomes) and gene guns can be used to put DNA into cells.
Viruses are also used as so-called vectors to “infect” human cells carrying defective genes with functional copies. That’s what parasitic viruses normally do – inject genetic material (their own, of course) into host cells.
Gene editing using CRISP-Cas9 isnt always fool proof. Why? How does gene therapy work overall?
People may mount an immune response against the virus, destroying both it and the good genes. Or, the virus may place its payload of genes into the human DNA but in the wrong place. This might cause cancer (why?).
Overall, current successes for gene therapy are quite limited, but there is great promise for the future, especially once the use of CRISPR-Cas9 kicks in.
What are stem cells? What are the different kinds?
Stem cells have the potential to develop into any kind (or almost any kind) of mature cell type. Not surprisingly, embryonic cells seem to be the most useful stem cells, called totipotent stem cells. Of course, embryonic cells have to develop into every kind of cell present in the adult body. Pluripotent stem cells are less versatile, and committed stem cells are the least versatile.
While it is convenient to separate stem cells into these three types, they are more like points on a continuum going from most to least versatile.
How can stem cells help is treat diseases?
If stem cells can be coaxed to develop into specific cell types, then we may be able to devise better treatments for such conditions as Parkinson’s disease (a brain disorder), spinal cord injury and Type I diabetes (and many more).
One clinical use of stem cells is in the treatment of certain kinds of blood cancer. A patient’s own blood stem cells are destroyed and replaced with blood stem cells from a healthy donor.
There’s lots of experimental work going on. One troubling observation is that stem cells sometimes develop into tumors rather than the desired cell type.
What are the two motivations for cloning a person and describe them
In reproductive cloning, I make a replica of the complete donor individual. For example, I might clone a dead child or spouse (there’s a pretty healthy industry in the cloning of dead pets).
In therapeutic cloning, I’d clone a very early embryo from which I would then harvest stem cells (remember, they are totipotent). Research on therapeutic cloning is going ahead in the U.S., but with strict regulations. Certain other countries also are moving ahead in research on therapeutic cloning.
Has a human been cloned yet?
We have cloned humans to early embryonic stages with the goal of obtaining stem cells (that’s therapeutic cloning). Claims have been made that humans have been cloned to birth or beyond (that’s reproductive cloning), but these claims haven’t been supported by any evidence
How have politics impacted stem cell research?
The George W. Bush administration put restrictions on federally-funded research on stem cells in the U.S. (such research was restricted, but not banned). Many scientists and some politicians feared that the U.S. might lose its edge if stem cell research shifted abroad to countries with fewer regulations.
With the advent of the Obama administration, restrictions on the use of embryonic stem cells were relaxed somewhat – which isn’t to say that regulations on and legal challenges to their use in research aren’t continuing.
