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Ch. 24 - Cancer Genetics
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All textbooksKlug 12th EditionCh. 24 - Cancer GeneticsProblem 29

Chapter 23, Problem 29

Skin cancer carries a lifetime risk nearly equal to that of all other cancers combined. Following is a graph [modified from K. H. Kraemer (1997). Proc. Natl. Acad. Sci. (USA) 94:11–14] depicting the age of onset of skin cancers in patients with or without XP, where the cumulative percentage of skin cancer is plotted against age. The non-XP curve is based on 29,757 cancers surveyed by the National Cancer Institute, and the curve representing those with XP is based on 63 skin cancers from the Xeroderma Pigmentosum Registry.

Explain why individuals with XP show such an early age of onset. 

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Hello everyone and welcome to today's video. So which of the following can be a symptom of scleroderma, pig Mentos um in Children and so were given certain symptoms that we need to select it from. But before we do that, let me quickly remind you of what this condition can cause. And it's basically a condition that makes it more difficult to repair cells after UV damage. So the UV damage is going to affect the DNA makeup of the cells and the cells are going to degrade normally. Our bodies can repair this but this, but the person that has this condition simply cannot do it as effectively. So they will have more extensive damage from just a few minutes of sun exposure. So let's go over answer choices. Knowing this answer choice A. We have severe sunburn after a few minutes of sun exposure. So something that would take a normal person hours to obtain this person with the condition listed is going to suffer after a few minutes. This sounds like it is a symptom so we're not going to cancel this out. Then we have answer to it is B and C. The appearance of records in sun exposed areas and dry skin after a few minutes of sun exposure is actually both going to be symptoms of the condition because like we said, it makes it more difficult to repair the cells. So the damage that sun exposure normally does is going to be more extensive and it's going to act faster on them. So because all of our answer choices are correct. We're going to select answer choice. The options are correct. As a final answer to our question. I really hope this video helped you, and I hope to see you on the next one.
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Textbook Question

The table in this problem summarizes some of the data that have been collected on mutations in the BRCA1 tumor-suppressor gene in families with a high incidence of both early-onset breast cancer and ovarian cancer.

Predisposing Mutations in BRCA1
Kindred    Codon    Nucleotide     Coding Effect     Frequency in
                               Change                                    Control
                                                                                Chromosomes    
 1901          24           -11 bp          Frameshift           0/180
                                                       or splice
 2082        1313         C→T           Gln→Stop            0/170
 1910        1756         Extra C        Frameshift           0/162
 2099        1775         T→G            Met→Arg            0/120
 2035         NA*          ?                  Loss of                NA*
                                                       transcript                                      _
Source: (1994). Science 266:66–71. © AAAS.

Although the mutations listed in the table are clearly deleterious and cause breast cancer in women at very young ages, each of the kindred groups had at least one woman who carried the mutation but lived until age 80 without developing cancer. Name at least two different mechanisms (or variables) that could underlie variation in the expression of a mutant phenotype, and propose an explanation for the incomplete penetrance of this mutation. How do these mechanisms or variables relate to this explanation?

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Textbook Question

Researchers have identified some tumors that have no recurrent mutations or deletions in known oncogenes or tumor-suppressor genes and no detectable epigenetic alterations. However, these tumors often have large chromosomal deletions. What are some possible explanations that could account for the genetic causes behind these tumors?

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Textbook Question

Skin cancer carries a lifetime risk nearly equal to that of all other cancers combined. Following is a graph [modified from K. H. Kraemer (1997). Proc. Natl. Acad. Sci. (USA) 94:11–14] depicting the age of onset of skin cancers in patients with or without XP, where the cumulative percentage of skin cancer is plotted against age. The non-XP curve is based on 29,757 cancers surveyed by the National Cancer Institute, and the curve representing those with XP is based on 63 skin cancers from the Xeroderma Pigmentosum Registry.

Provide an overview of the information contained in the graph. 

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Textbook Question

Although cancer is not a contagious disease in humans or other vertebrates, there have been rare cases in which cancers have spread from one organism to another. Describe three cases of these contagious cancers and what conditions might have led to their appearance. For an introduction to this topic, see http://www.cancer.org/cancer/cancerbasics/is-cancer-contagious.

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