What are genetic disorders?
Genetic disorders are diseases transmitted genetically and there are many ways that they can be passed along. Since a baby would receive 23 chromosomes from the mother and 23 chromosomes from the father, these are what determine whether you will get a genetic disease or not. It is all based on the past history of your family. If a mother or father has a dominant gene for a disease, that is already a 50% chance that the baby could end up with a genetic disease. Another way that a genetic disorder can occur is by the mutation and abnormality of genes. Genetic disorders are passed on through the genes that you inherit from your parents. Everything about you is programmed by genes on your DNA for example; your eye color, tongue rolling ability, gender and whether you have hairy knuckles or not. Each baby gets one set of DNA from the mother, and one from the father and it is how those genes combine together.
(This is a picture of some strands of DNA)
What is breast cancer?
The genetic disorder that I have researched is Breast Cancer. However, there only theories about how people get breast cancer, and scientists are only in the discovery phase with breast cancer genes. Due to this, I will compare cancer to Xeroderma Pigmentosa because the way each of these disorders are transmitted genetically are different.
Cancer is known as mitosis out of control, this means that cells reproduce way to fast and there are so many cells that they just bunch up together and form tumors. Knowing that that is what cancer is, breast cancer is when a bunch of breast cells bunch up and form a tumor. If the cancer is not treated, it can metastasize, this means that the cancer will spread to other parts of the body. The two most common types of breast cancer are ductal carcinoma and lobular carcinoma. Ductal carcinoma is when the cancer starts to form in the milk ducts of the breast. Lobular carcinoma is when the cancer forms in the lobules. Lobules are the glands that produce milk.
(This is a picture of a mammogram, on the left side it is a picture of a cancerous breast, and on the right side is a picture of a normal breast)
With breast cancer, not everyone that has breast cancer will have the genefor it. In fact, most cases occur in people without the gene for it. There may be a generic component but at this stage in research, scientists don't know what causes breast cancer in people without the gene. But they do know that if you have the gene, you will have about an 80 to 90 percent chance of getting it because for some reason, people with the gene are more susceptible to getting it. What scientists do know is that there isn't only one breast cancer gene, there is two; BRCA 1 and BRCA 2. They also know that it is only a 5 to 10 percent chance that it is hereditary and can be passed along from parents to children. This is why it is not easy to explain how breast cancer is inherited based on genetics and also why I have given an example of how xeroderma pigmentosa is genetically inherited. It really goes to show the complexity of breast cancer and that it isn't as straightforward as most diseases.
Three breast cancer symptoms include a painless lump in the breast, something abnormal seen on a mammogram, or vary rarely, blood from the nipple. Treatments for breast cancer include surgery, chemotherapy, and radiation. There are two different types of surgeries that doctors can perform to try to remove the cancer tumor. The first type is a breast-conserving surgery, this surgery is when the doctors only remove part of the breast that is affected. The other type of surgery is a mastectomy, this surgery is when the doctors remove the entire breast. However, there are different types of mastectomies. The two most common are a simple mastectomy and a skin-sparing mastectomy. A simple mastectomy is where the doctors do not reconstruct the breast using lymph node tissue after removing it. A skin-sparing mastectomy is when the doctors immediately reconstruct the breast using lymph node tissue (usually from under the armpit) after removing it. Some side affects of the treatments include; weakness and fatigue, hair loss, lowered resistance to infections (low white blood cell count), bleeding, diarrhea, premature menopause,weight gain, nausea and vomiting, mouth soreness, loss of appetite , bone and joint pain, wounds heal very slowly. However, this is only a few of the side affects, the list goes on and on. Each person reacts differently to treatment and will have different side affects, this also depends on the type of medication that the person is taking.
What is Xeroderma Pigmentosa?
Xeroderma pigmentosa (XP) is a genetic disease where a person is very sensitive to the ultraviolet rays from the sun. This condition mostly affects the person's eyes and skin that is exposed to the sunlight. Symptoms of sunburn, blisters, dry skin (xeroderma), changes in skin coloration (pigmentosa), freckling and tanning can develop within minutes of the children being exposed to the sun. Other symptoms include scaling of the skin, spider-like blood vessels, crusting of the skin, and oozing raw skin surface. 50 percent of children who have this disease develop their first skin cancer by the age of ten years old. People who have this disease develop many skin cancers in their lifetime. This is because when a person with this disease gets sunburn, their skin does not heal and it just keeps getting worse and worse. The skin becomes very thin after a while and this is when the color of the skin changes. The most affected areas of this disease are the eyes, face, lips, tip of tongue, scalp, and eyelids. Since this disease is an autosomal recessive disease, a baby could inherit it if it got one XP gene from its mother and one XP gene from its father.
Possible outcomes of the offspring:
- X is dominant gene for a child that is not affected by the disease
- x is a recessive gene for a child affected by the disease
| x | x | |
| X | Xx | Xx |
| x | xx | xx |
This punnett square represents the results of the children of a woman and a male. The couple would have a 50% chance of having children that are not affected by the disease but will be carriers of the gene for the disease and a 50% chance of having children who will be affected by the disease.
| X | x | |
| X | XX | Xx |
| X | XX | Xx |
This punnett square is for another couple. This couple would have a 50% chance of having children who are not affected by the disease and a 50% chance of having children who are not affected by the disease but who are carriers of the disease.
| x | x | |
| x | xx | xx |
| x | xx | xx |
This punnett square is for another couple who both have the disease. Unfortunately, 100% of their offspring will be affected by the disease.
(This is a picture of a child who has xeroderma pigmentosa)
Controversies with breast cancer:
A controversy with the breast cancer genes is that doctors don't have the whole picture. The answer to curing breast cancer is not completely based on genetics and scientists and doctors don't know what the other causes are. A theory that researchers believe is that cancer is caused due to environmental reasons and not as a result of genetics. Another theory is that wearing underwire bras cause breast cancer but none of these theories have been proven. Another controversy involves the technology of genetic altering. Some questions that are being asked are should we be doing this at all? Where does it stop? and, once people have the technology to alter peoples genetics, will people use the technology for bad reasons?
What is gene therapy?
Gene therapy is when doctors use genes for treatment or prevention of diseases. Gene therapy is only being tested at the moment and if it is successful, it could lead to doctors using this method instead of using medicines to treat diseases. Basically what it is, is when doctors put genes into a person to try to make the new genes take over the job of the genes that have a disease or disorder. The study of gene therapy is actually focused mainly on cancer at the moment. There are multiple uses for gene therapy, first, for the genes to take over old genes that no longer function properly. Two, to switch a normal gene for an abnormal one. Three, to try to repair the gene that is damaged and diseased. Four, to alter the genes, for example; deciding the traits, appearance, or gender of your baby. However, this is an example of how gene therapy could potentially go way to far. This is the stage when people have taken advantage of technology and there are many controversies regarding this subject. The last way that gene therapy could possibly be used for is called a "spindle transfer", this is when doctors would fix a whole mitochondria that could potentially have non-functioning mitochondrial DNA.
Sources:
http://www.givf.com/geneticservices/howisgeneticdiseaseinherited.shtml
http://www.webmd.com/breast-cancer/guide/treatment-side-effects
http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-treating-surgery
http://www.breastcancer.org/risk/factors/genetics
http://ghr.nlm.nih.gov/handbook/therapy/genetherapy
http://ghr.nlm.nih.gov/condition/xeroderma-pigmentosum
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002438/
http://www.news-medical.net/health/What-is-Gene-Therapy.aspx
Image Sources: