Biology
In adults, over 90% of all cancers are either adenomas (adenocarcinomas) or carcinomas, including cancers of the skin, lung, colon, breast, and prostate. Which one of the four basic tissue types gives rise to most cancers? Give two reasons why this tissue is more likely to produce cancerous cells.
Skin cancer is the most common[footnoteRef:2]. Each year over 2 million people are treated for basal cell and squamous cell carcinoma in the United States alone. The next most common cancer type is prostate cancer. [2: http://www.cancer.gov/cancertopics/wyntk/skin]
The risk of skin cancer is increased by exposure to UVB radiation, whether by natural sunlight or tanning beds[footnoteRef:3]. Studies in skin-humanized mice show UVB induced DNA damage, p53 expression, and epidermal disorganization[footnoteRef:4], changes that would be expected to increase cancer risk. [3: http://www.cancer.gov/cancertopics/wyntk/skin/page5] [4: Garcia et al., 2010. Amer. J. Pathol., 177, 865-]
Genetics also plays a role on many levels[footnoteRef:5]. Persons with fair skin, blue or gray eyes, lots of freckles, or red and blond hair will tend to burn rather than tan when exposed to sunlight. The redness produced when the skin is sun burned is an indication of skin trauma, including DNA damage[footnoteRef:6]. An increased risk of developing melanoma and other types of skin cancer can run in some families as well. [5: http://www.cancer.gov/cancertopics/wyntk/skin/page5]...
Brittany and Joshua are physically normal but they have a daughter with galactosemia, an autosomal recessive disease. The daughter is homozygous recessive. What are Mary and Joe's genotypes?
An autosomal recessive disease can only manifest if an individual contains two mutated copies of the same gene. In the case of galactosemia the genes known to cause this disease are galactose-1-phosphate uridylyltransferase, galactokinase, or galactose epimerase[footnoteRef:7]. Since the parents are physically normal then both must be heterozygous carriers for the same mutated gene. [7: http://ghr.nlm.nih.gov/condition/galactosemia]
3. In recent years more mothers are breast-feeding their babies. At the same time, mothers have been protecting the skin of babies from sunlight, to reduce UV exposure. A side effect of this protection has been weak bones and other symptoms of rickets in breast-fed babies.
a. Mothers who are breast-feeding are told to give the babies Vitamin D, and to encourage young children to play outside. Why? The answer does not involve obesity.
The gradual shift from a primarily agrarian society to an urban one has reduced the amount of sun exposure children receive. When exposed to sunlight cholesterol (7-dehidrocholesterol) in healthy human skin is converted to vitamin D3[footnoteRef:8]. This vitamin is important for…
