In grade eight Science we learned about the basic unit of life, cells, and we started to learn about human body systems as well. It was in grade eight science that I first heard about Deoxyribonucleic acid or DNA and how it carries all the genetic information of cells. In grade nine Science we are learning more about DNA, about how the nucleus controls the function of the cell, and about both asexual and sexual reproduction It has been sixty-five years since James Watson and Francis Crick published their remarkable paper in the British Science Journal Nature on 25th April, 1953 titled ‘Molecular Structure of Nucleic Acid.
‘ The structure they had unraveled was the double helix of Deoxyribonucleic acid or DNA. (Refer to Fig. 1: The Double Helix). They began their paper with a simple statement: “We wish to suggest a structure for the salt of deoxyribonucleic acid (D.
N.A,). This structure has novel features which are of considerable biological interest.” Their paper is too complicated for me to understand in grade nine but perhaps when I am in grade 12 or at university I will sit and read their paper carefully.
Fig. 1: The Double Helix (Watson and Crick, Nature, 1953)How Watson, Crick and Rosalind Franklin unraveled the structure of DNA is a remarkable story. They extracted DNA out of cells, then made it into a crystal of DNA and then used X-rays to take a picture of the structure of Deoxyribonucleic acid (refer to Fig. 2: Rosalind Franklin’s X-ray diffraction, DNALC). Fig.
2: Rosalind Franklin’s X-ray diffraction, DNALCGreat interest in DNA began around the time they won the 1962 Nobel Prize. After winning the Nobel Prize Dr. James D. Watson wrote a book called ‘The Double Helix: A Personal Account of the Discovery of the Structure of DNA’ (Dr. Watson’s book is available as a pdf through the University of Washington).
” In 2005 Dr. James Watson gave a Ted Talk address titled: How We Discovered DNA. From his own words we find the following interesting observations:”And so I didn’t really get happy until 1960, because then we found out, basically, you know, that there are three forms of RNA. And we knew, basically, DNA provides the information for RNA. RNA provides the information for protein. And that let Marshall Nirenberg, you know, take RNA — synthetic RNA –put it in a system making protein .
. . So that’s the first cracking of the genetic code, and it was all over by 1966.” One area where our understanding of DNA can be used is in genetic counseling. In his 2005 Ted Talk Dr. James Watson gives several examples of how our understanding of DNA has allowed us to better understand the genetic basis to a number of afflictions like cancer, autism and schizophrenia.
There are two basic ways that genetic counseling can be done. One is to do it clinically, where the patients are asked to relate their family histories, with an emphasis on familial diseases such as heart disease, cancer, mental health issues, congenital afflictions and the like. Clinical counseling is based not on a specific knowledge of the actual state of the patient, but on a statistical model of what might be the underlying cause of their affliction, or in the case of a woman who might be wanting to mother a child, what are the odds that the offspring may carry a disease. Two examples of diseases that can be counseled clinically are first, beta thalassemias, which is an inherited genetic blood disorder caused by reduced or absent synthesis of the beta chains of hemoglobin (which in its mild form caused chronic anemia, and in its major form can be fatal), 7 and second an affliction known as Rh incompatibility. In the past, throughout much of the industrialized world, it was required that the man and the woman had to have blood tests before they decided to marry. This was because of the health risks to the child because of possible RH – factor incompatibility Rh incompatibility is a condition that increases risk of anemia, stillbirth, premature birth, and immune system issues for the baby.
In the mid-1960’s the Rh incompatibility affliction was sorted out by a series of simple injections. Genetic counseling today is able to decide whether this injection is needed by the mother to be. The second approach to genetic counseling is to draw blood sample from the patient and then do an analysis of the DNA in the blood.
In the case of beta thalassemias a person can be assessed for the severity of their affliction and, in some cases, treated. In the case of a life threatening beta thalassemias affliction, the patient can opt for gene therapy and a bone marrow transplant (blood is produced in the bone marrow). Gene Therapy and bone marrow transplant procedures like this is done at Vancouver Hospital. Today blood samples can be used to also assess a patient’s risk for several forms of cancer, such as breast cancer, ovarian cancer and prostate cancer.
Techniques like Nuclear Medicine, (including Positron Emission Tomography) and drug therapy can then be used to both treat and monitor the treatment of the patient.One area of genetic counseling of particular concern is in the increase of male and female hypospadias, which is when the urethra does not fully develop and properly form while a baby is in their mother’s uterus, requiring corrective surgery at age four or five. The urethra is how the urine passes from the bladder to the outside. Hypospadias mostly afflicts male babies, but more and more female babies are being born with this congenital disorder and the rate of occurrence has increased at an alarmingly increasing rate in the industrialized world, suggesting that an endocrine disruptor is the cause. Since 1960 the rate has almost tripled to 1 in 250, and hypospadias is the single largest congenital affliction by far of newborns. (refer to Fig.
3: Increase in Hypospadias Rates in US 1970 to 1997). Fig. 3: Increase in Hypospadias Rates in US 1970 to 1997Similar trends have been noted internationally. This rate is considerably higher than other afflictions such as autism, and dwarfism, and needs to be addressed either clinically or through other means of counseling, and at the very least through an environmental health perspective (counseling on nutrition, for example).