Introduction

Chapter 1. Chapter 10: Mutations and Cancer

Interactive Study Guide
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Welcome to the Interactive Study Guide for Chapter 10: Mutations and Cancer. This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Fighting Fate:

When cancer runs in the family, ordinary measures are not enough

DRIVING QUESTIONS

  • What are mutations and how can they occur?
  • How does cancer develop and how can people reduce their risk?
  • Why do people with “inherited” cancer often develop cancer at a relatively young age?

Driving Question 1

What are mutations and how can they occur?

Why should you care?

Some mutations may be caused by mistakes made during DNA replication that aren’t repaired by normal cellular mechanisms. Even though such mistakes are very rare during each replication event, replication itself is so frequent that mutations add up over time. Mutations give rise to new alleles – i.e., alternative forms of a gene that can be passed from parent to offspring.

For most women, the risk of developing breast cancer is 12-15% (1 in 7 women). For women with a mutation in the BRCA1 gene, however, the lifetime risk of developing breast cancer is 40-80%. Moreover, the mutation also creates a 20-50% lifetime risk of developing ovarian cancer. The mutation is hereditary and involves only a small change in the normal BRCA1 DNA sequence.

Lorene Ahern inherited her mutated BCRA1 allele from one of her parents. But mutations – including those that increase cancer risk – can be caused in other ways as well. Understanding the causes of mutations can help us make wise lifestyle choices that can reduce our own cancer risks.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Compare and contrast the normal BRCA1 allele with the allele that increases the risk of breast and ovarian cancer.
  2. Illustrate and describe how errors in DNA replication and repair can result in mutations.
  3. Compare and contrast the three different ways in which DNA mutations may be acquired.
  4. Predict whether a mutation in the DNA of different parental cells will be inherited by their offspring.

Infographic Focus

The infographics most pertinent to the Driving Question are 10.1, 10.2, 10.3, 10.4 and 10.5.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
A mutation occurring in gametes; passed on to offspring.
Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.
Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.
A change in the nucleotide sequence of DNA.
A mutation that occurs in a body (nongamete) cell; not passed on to offspring.
Table
9
Try again.
Correct.
Incorrect.

Compare and contrast the normal BRCA1 allele with the allele that increases the risk of breast and ovarian cancer.

1.

Compare the DNA sequences shown in Infographic 10.1 for the normal and mutated BRCA1 alleles. Based on your understanding of transcription and translation, how different would the proteins produced by these two alleles be? (Review Ch. 8 as necessary, with particular attention to the structure of mRNA codons and how they code for amino acids.)
The mutated BRCA1 allele has an insertion of a base pair at the 8th position. This causes all the following amino acids to be different from the normal BRCA1 allele. So the two proteins produced by the two alleles would be very different.

Describe how errors in DNA replication and repair can result in mutations.

2.

Describe the three possible outcomes of a mistake at a single nucleotide during DNA replication.
A single nucleotide mistake during DNA replication can be repaired correctly, repaired incorrectly or not repaired at all. All three would result in different alleles of the gene.

Compare and contrast the three different ways in which DNA mutations may arise.

4.

Based on Infographic 10.5, what are the three major ways in which an individual may acquire DNA mutations?
DNA mutations can be inherited, they can arise through mistakes in DNA replication and they can be directly caused by environmental insults (mutagens and carcinogens like smoking and UV light).

Predict whether a mutation in the parent DNA will be inherited by their offspring.

7.

Will a child inherit the following mutations from their parent? Why or why not?

A mutation caused by a chemical that affects the mother’s egg cells.
Yes; this is a mutation of a germ-line cell (gamete).

Review Questions

10.

Mutations in DNA can be caused by: (mark "true" for all that are correct)

a. Smoking cigarettes

b. Heredity

c. UV sun tanning beds

d. Char

Correct.
Incorrect.

Driving Question 2

How does cancer develop and how can people reduce their risk?

Why should you care?

Cancer is a disease caused by problems in the cell cycle control mechanisms. Two types of genes control the frequency and timing of cell division. Proto-oncogenes normally control how often a cell divides (often by responding to external signals that initiate division), while tumor suppressor genes – including BRCA1 – typically slow down cell division, repair damaged DNA, and kill cells whose DNA is irreparably damaged. Lorene Ahern’s mutated BRCA1 allele increases her risk of breast cancer because the protein it produces cannot repair damaged DNA. If enough DNA damage accumulates in a group of cells over time, cancer is a likely result.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Illustrate and describe the process by which a mutation can cause cancer.
  2. Compare and contrast the roles of proto-oncogenes and tumor suppressor genes in regulating the cell cycle.
  3. Explain how mutations in proto-oncogenes and tumor suppressor genes can increase cancer risk.
  4. List and explain some ways in which people may reduce their cancer risk.

Infographic Focus

The infographics most pertinent to the Driving Question are 10.3, 10.4, 10.5, 10.6 and 10.7 and Table 10.2.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
A gene that codes for proteins that monitor and check cell cycle progression. When these genes mutate, tumor suppressor proteins lose normal function.
A noncancerous tumor that will not spread throughout the body.
Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.
A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually.
A mutation occurring in gametes; passed on to offspring.
A gene that codes for a protein that helps cells divide normally.
A change in the nucleotide sequence of DNA.
Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.
A cancerous tumor that spreads throughout the body.
A mutation that occurs in a body (nongamete) cell; not passed on to offspring.
Table
9
Try again.
Correct.
Incorrect.

Illustrate and describe the process by which a DNA mutation can cause cancer.

14.

Create your own version of Infographic 10.4 by following these 4 steps:

Copy the normal allele sequence shown in the illustration.
TAC GGC AGC CTA CCT normal allele

Compare and contrast the roles of proto-oncogenes and tumor suppressor genes in regulating the cell cycle.

19.

Use Infographic 10.6 to answer the following questions:

Explain why the symbol for proto-oncogenes is a green “go,” while the symbol for tumor suppressors is a red “stop”.
The symbol for proto-oncogenes is a green “go” because the normal function of these genes is to signal cells to progress through the cell cycle. In contrast, the symbol for tumor suppressors is a red “stop” because the normal function of these genes is to signal the cells to pause during the cell cycle in order to fix mistakes.

Explain how mutations in proto-oncogenes and tumor suppressor genes can increase cancer risk.

22.

What is a mutated proto-oncogene called?
An oncogene.

List and explain some ways in which people may reduce their cancer risk.

25.

What are some measures a person can take to reduce their risk of cancer? How do these measures reduce cancer risk?
To reduce their cancer risk, a person could wear sunblock to limit their exposure to UV radiation, thus preventing mutations caused by this mutagen. They could also avoid smoking cigarettes that contain many carcinogens that could mutate their DNA.

Review Questions

27.

The difference in the proteins produced by a normal allele and a mutated allele is:

A.
B.
C.
2
Try again.
Correct.
Incorrect.

Driving Question 3

Why do people with “inherited” cancer often develop cancer at a relatively young age?

Why should you care?

Lorene Ahern’s mutated BRCA1 increases her risk of developing breast cancer. However, it will not cause breast cancer by itself. Cancer cells have many abnormal traits: they divide without normal checks even when crowded, invade nearby tissues, cause new blood vessels to form that supply them with nutrients, and can eventually spread to distant locations in the body. These traits are the products of multiple mutations accumulating over time. For people who inherit high-risk mutations, this time is shorter than normal.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Outline the steps involved in a tumor becoming cancerous and explain why more than a single mutation is required.
  2. Using this model, explain why inherited mutations increase a person’s risk of developing cancer at an earlier age than normal.

Infographic Focus

The infographics most pertinent to the Driving Question are 10.1, 10.5, 10.6, 10.7, and 10.8.

Outline the steps involved in a tumor becoming cancerous and explain why more than a single mutation is required.

30.

Describe the steps outlined in infographic 10.7 by which a tumor may become cancerous by completing the following table:

Step A Step B Step C Step D
Describe the mutation

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.
Describe its consequences

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.

Fill in below:
A single mutation in a tumor suppressor gene associated with DNA repair.
Table

A single mutation in a tumor suppressor gene associated with DNA repair.

Using this model, explain why inherited mutations increase a person’s risk of developing cancer at an earlier age than normal.

32.

Using this model, explain why inherited mutations increase a person’s risk of developing cancer at an earlier age than normal.
Inherited mutations increase a person’s risk of developing cancer at an earlier age because they already have a mutation in a gene that is known to control the cell cycle in some way. Eventually, more mutations will happen and add to the problem. In these people, the initial step is already done.

Review Questions

34.

A mutation in a proto-oncogene that causes the protein to be non-functional will lead to cancer.

A.
B.
2
Try again.
Correct.
Incorrect.

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