BIO exam review

BIO exam review - 426 Chapter j8 Cancer: IJncontrolled Cett...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
426 Chapter j8 Cancer: IJncontrolled Cett Division and Differentiation ,Joh^*-, M. b, (rora) . Ar^on blolSy .. ca^<z#s a-nal cum,eqf issues l dt .d, . Sa-r F1a. ,.;=,-- CA ,. Pear=o"t *+,ja.n,i,t Cut wri\s. . .+aG- 1e8. : :: I 1*i.it l t!r'.;.1!!a.{::' A car analogy demonstrates how a cell progresses toward cancer. At first your new car runs very well. As time goes on a few parts wear out, but you manage to keep it in good repair with regular service checkups. But as the car gets older, the need for repairs gets more frequent, and you aren't alwals able to keep up with them. Now the suspension needs re- placing, the tires are worn out, the accelerator pedal sticks occasionally. and the brakes are thin. No single defect is enough to cause an accident, but together they spell trouble. There may come a moment when you may not be able to control the car, and you'll have an accident. The same sort of progression occurs within cells. In fact, the single most imponant factor in the development of can- cer rnay be age. Skin cancer is uncommon before adulthood, even though most severe sunbums occur during childhood. Recall from Chapter 4 that the outerlayers ofyour skin are .ontinually being replaced by basal cells located at the base of the epidermis. The basal cells of a child's skin haven't beerr through very many cell divisions yet-they are still in gooci repair. But decades latet alier thousands more cell divisions and a few more sunburns, those same basal cells are about worn out. Cellular repair mechanisms fail more frequently; mechanisms controiling cell division become less effective. First there's dysplasia, then cancer. The cells are out of control. In addition, your parents may carry. a few of the cancer_ promoting mutations that have accumulated in the precursor cells to human eggs and sperm during the course ofiuman evolution. These rare heritable mutali,cns may not be enough to guarantee cancer, but they do incre ase your heitcble suscE_ tibiliry. If six mutations are required lo produce cancer, for ex_ ample, you could inherit five mutations and still be cancer free. This is why, even in families with a history ofcancer, some siblings develop the disease and others io not. The multigene basis of cancer also explains why it is possi_ ble to develop cancer even if there is no fimily history. Remem- ber that we all inherit a slightly different combination ofo,,. parents' genes, and ifyou happen to get mutated genes from boti parents, you could be ar greater risk than ei*ter of them. (We discuss gener-ic inheritdnce in more dera jl in Chaprer lg.) The process oftransforming a normal cell into i cancer_ ous one is called carcinogenesis. A carcinogen is any
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

BIO exam review - 426 Chapter j8 Cancer: IJncontrolled Cett...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online