Question

1. State one of the reasons, why cancer does not occur more often than it already does.

2. State one of the four general ways, a proto-oncogene is turned in to an oncogene.

Answer 1

1.By far the biggest risk factor for most cancers is simply getting older. More than three-quarters of all people diagnosed with cancer in the UK are over the age of 60.

And this is because cancer is a disease of our genes – the bits of DNA code that hold the instructions for all of the microscopic machinery inside our cells. Over time, mistakes accumulate in this code – scientists can now see them stamped in cancer’s DNA. And it’s these mistakes that can kick start a cell’s journey towards becoming cancerous.

The longer we live, the more time we have for errors to build up. And so, as time passes, our risk of developing cancer goes up, as we accumulate more of these faults in our genes.

In the graph below, you can see how UK life expectancy has increased over time and the number of people living into old age is higher than ever before.

This means there are now more people than ever living to an age where they have a higher risk of developing cancer.

But we can stack the odds of avoiding cancer in our favour. Things that happen throughout our lives can speed up – or slow down – the rate at which errors occur in our genes. These include things we can control, and some we can’t.

They include our lifestyle, our genetics & family history, our exposure to viruses, the job we do, the air we breathe – and they can all play different roles in our overall risk of developing the disease.

2.A proto-oncogene is a normal gene found in the cell. There are many proto-oncogenes. Each one is responsible for making a protein involved in cell growth, division, and other processes in the cell. Most of the time, these genes work the way they are supposed to, but sometimes things go wrong.

An activating mutation of one of the two alleles of aproto-oncogene converts it to an oncogene, whichcan induce transformation in cultured cells or cancer in animals. Activation of a proto-oncogene into an oncogene can occur by point mutation, gene amplification, and gene translocation.

• Point mutation-This mutation alters, inserts, or deletes only one or a few nucleotides in a gene sequence, in effect activating the proto-oncogene. According to the American Cancer Society, most of the mutations that cause cancer are acquired, not inherited. This means that you aren’t born with the gene error. Instead, the change happens at some point during your life.Some of these mutations result from an infection with a type of virus called a retrovirus. Radiation, smoke, and other environmental toxins may also play a role in causing mutation in proto-oncogenes. As well, some people are more susceptible to mutations in their proto-oncogenes.