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University of Colorado School of Medicine
 

Cell Biology

Bridget Coughlin, PhD


 
Why do platelets become "slippery" and not clot when they are overproduced? My mother had a cancer condition in which this happened and had bleeding problems which had to be treated with uracil to control the bleeding.

Some cancers can cause a high platelet count either by causing damage to tissues, causing blood loss (for example from the bowel) or by erroneously producing a response from the immune system that stimulates the bone marrow to produce platelets. Usually this is not a problem, but on rare occasions there can be abnormal clotting or bleeding, which would indicate that the platelets are not only too many, but also abnormal in some way, probably due to the disease process. I don’t know about uracil as a drug, sorry.

I've read that mitochondrial DNA is becoming a big area of research. What do we know about its significance?

As Dr. Coughlin said, most of the 37 mitochondrial genes are involved in energy production within that little dynamo. Any of them can be damaged by mutation. The inheritance is from the mother to the boy or girl children. However, because there are many mitochondria in the ovum, not all will have the mutation, so the disease may vary from unapparent to severe. There is a good article in Wikipedia: http://en.wikipedia.org/wiki/Mitochondrial_disease.

Could you explain the role of histones in the coiling of DNA?

To get a meter of DNA into a nucleus that’s only a few micrometers across, you have to do a lot of coiling! The first step is to wrap the double helix around a core of histone proteins called a nucleosome; they are placed about every 180 base pairs, and you have a total of about 3 billion base pairs. The histones are modified by several enzymes, increasing or reducing their net electrical charge, which tightens the DNA coil or loosens it up so a gene can be copied to RNA.

What specific role do cyclins play in the formation of cancer cells?

Cyclins are a large group of proteins involved, as the name suggests, in the passage of any cell through the cell cycle, called mitosis, or cell division. There are several mutations that occur that cause a cell to divide and the just keep dividing; it is one of the mutations that is frequent in cancer. As we’ll see in the last lecture, it’s not the only mutation...

I also believe Rosalind Franklin was responsible for the discovery of the double helix structure of DNA?

Indirectly. She did the critical X-ray crystallography experiments that revealed the structure, but had not gotten around to interpreting the data as she was occupied by another project. But she showed the X-ray picture at a meeting that Watson & Crick attended, and they instantly knew what it meant. They should (JJC’s opinion) have told her and asked her to co-author the paper with them; but they didn’t. However, she now has a medical school named in her honor in Chicago (http://www.rosalindfranklin.edu/) and neither Watson nor Crick do.

What is the difference between Crisco, butter-like spreads, butter and oil?

There are chemical differences, and these products get reformulated all the time; only a professional nutritionist could keep up. Crisco is made partly with hydrogenated oils, which are saturated. Butter is probably better for you; but it is very high calorie like all fats (9 kCal/gram) so use it in moderation. Many doctors think olive oil is about the perfect lipid.

What are some healthy sources for glucose when white sugar, white refined pasta and cereals are eliminated from your diet?

Whole grains are good; they have considerably lower glycemic indexes that food made with white flour. There are many of them, try different ones and see what you like. Bob’s Red Mill markets a wild array of exotics, many of them even at stores like Safeway or King Soopers. Fruit are fine; they have fructose but no one has implicated that source as harmful. Honey? The jury is still out on that.

If you don't eat sugar how does your body get enough glucose?

The body is really good at utilizing starch, which yields glucose when broken down by enzymes in saliva and the intestines. Starch is mostly in plant foods, like grains and fruits. It is a healthier source of carbohydrate than plain sugar (though a bit of sugar now and then is very nice!)

How do outside stimuli effect SNPs?

Single nucleotide polymorphisms are the little differences between my genes and yours; the sort of thing that gives blue or brown eyes, for example. A technical word is “alleles.” So we all have lots of these; and average person many have 300,000 differences from the “standard” human genome. Anything that can change the chemistry of DNA could cause a new SNP; this could be things in food, smoke, sunlight, and just the occasional error that all things are prone to. New SNPs are rare; at each cell division, the risk is less than 1 in a million ant a particular site on the DNA will be changed.