Chapter 1. Chapter 10: Mutations and Cancer

1.1 Introduction

Interactive Study Guide
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Polaris Trail

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?

1.2 Driving Question 1

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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
BBZUQ8LO98pv/rqwFvHUW32wJUTWBOzdF3Ugjo//o87XPo8jUAirDB/dBe4QBKQtOVzQmxsQ0v3DKEYVoMZkR0spNRMHVjHv A mutation occurring in gametes; passed on to offspring.
H3oSCnFcdmDFpPv0PRQ/NWBVyMyYa3ul8cSDw9JMwd3pXgjWXg1PwzHJv4Fq0dp9Wh6fpKazd8WfF8MdEGw6uVXOIPjxl6aV Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.
YWHjbFu32LtlEqAtTR0L3wmtYplui4Ui6eUMApmaCUJceQ76Etoq2ZSRuYwPgg81g9yuyxUXMZfwkAH9yS9IH7aK2iOz4GOl Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.
9/wUGq2QlngpvS1QQvlNNCT3ASC6jRyEqmdPHL5Wc8sRy7HJ+CFTrQFvKR2q651dVZedG8at5jRt4GzzxTcwUfFoFFaEo9mt A change in the nucleotide sequence of DNA.
5ySSJjEMnKIXTnm+nwx1EHpNfhROJuIdEPVpiXuucE0Zoth3huGjOh2BX+yALummMhzaENsHmW89XLu4rGfojSGmDP39hD6C A mutation that occurs in a body (nongamete) cell; not passed on to offspring.
Table
9
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Compare and contrast the normal BRCA1 allele with the allele that increases the risk of breast and ovarian cancer.

Question 1.1

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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.

Question 1.2

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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.

Question 1.3

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Alleles are slightly different versions of the same gene. Mutations cause these differences between alleles.

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

Question 1.4

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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).

Question 1.5

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These mechanisms are similar in that they all produce mutations in the DNA that could lead to cancer. They are different in that some preexist, like heritable mutations and some are acquired throughout a person’s life, like exposure to environmental pollution.

Question 1.6

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Yes, personal lifestyle choices can affect your likelihood of acquiring DNA mutations. For example, a person that repeatedly tans in a tanning booth with no sunblock are exposing themselves to a high amount of UV light which may cause mutations. Or the risk of acquiring DNA mutations is very high for someone who choses to smoke cigarettes. These are personal choices that can affect the amount of DNA mutation that occurs throughout a person’s life.

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

Question 1.7

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

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Yes; this is a mutation of a germ-line cell (gamete).

Question 1.8

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No, this is a mutation of a somatic cell (nongamete).

Question 1.9

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No, although this mutation affects the LEVEL of a germ-line cell (in this case, sperm) it is still a mutation in a somatic cell and in not passed on to offspring.

Review Questions

Question 1.10

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

a. Smoking cigarettes 2YvaXR/y8mhoD5Q0hHYKqg==

b. Heredity 2YvaXR/y8mhoD5Q0hHYKqg==

c. UV sun tanning beds 2YvaXR/y8mhoD5Q0hHYKqg==

d. Char 2YvaXR/y8mhoD5Q0hHYKqg==

Correct.
Incorrect.

Question 1.11

True or False: Tumor suppressor genes suppress tumors by pausing the cell cycle so a dividing cell can make repairs. 2YvaXR/y8mhoD5Q0hHYKqg==

Correct.
Incorrect.

Question 1.12

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2
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Question 1.13

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2
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1.3 Driving Question 2

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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
BqtvYpvj71SKcXH+Bu/V+OpAovzh6JBMswZup5rxn69w9VaM2bMCO/lOZD9iIjY8hTLzQZaaHY1yTsbmD8NbAGRM2QtvXl4HPvRo+z3yXo5uoICM9NPUVJudxSW2pWFRnCyovprtZBlbS5isDEVhUvvx2Dlb7E8+A+JFrzFLHTlbDcJ5YXKo1MmI4b15fiFE A gene that codes for proteins that monitor and check cell cycle progression. When these genes mutate, tumor suppressor proteins lose normal function.
oLd+wHQHloW6uKVBwNZEHyMcdVm5Yt3Zd4835Y4jMTTyioea+I13P9jTQzM3LTib6IuCIxIsl9ZYj4IyhNA03tYj+Zjho52HsLm9+JWuVDKNBk+d00VCUAFTvb0Y1OyCRdS5+X2Mt6vp/4+hjVpEfmOIyuQjmWQHRuIm2pZGnwdX9eT5FFVTc1vRtZbxjNug A noncancerous tumor that will not spread throughout the body.
f66mKDq31nV7R6Av0qw/+IoI05W3h67POT+hfCBLms0JgxTMD9SWd1eIAvLWX9g8dr67tl9rB82lvUyuvCj9BjyOPEkZYFWFMu5zUvW1bCKMppFwKz2uISyvskWkNUcg+DTy2k4GfnhjbmEs677vc6g0pj9HboSCQJLrRm7QwUeOUN6QJMloD75BC/k/Xz4e Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.
9FraIbWpzNaI7rxjye6FgKkhBcoLoHfYjvuODwthh5++xJZwuU9f/vBvqAX5QagQKJOcE/Cj2q02eThec1S7zxPc8sTWa6Q3Rhkrb7309Lah1LVihogAxCTwJYkIn+7CQvKAoxUDQMXGeHuemrVbfN0m4HQZTI9CUZH3B2ZcjhiON6+xqAgY47iHa7rCmy4X A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually.
aHUlwpPrSwa+eqO32Kx9glJJtuR6J8EUQfeZzU38zniAcATA1LO8XW0BJ6W0RjZo1NUweKPbYnXQb88IDz6sdlIH47OntsrD9dVMfb9v3/wVSDFGUkEo/H2tIOhBhl/DBD4ss92bLFZ/UyauXrii2O1kbo85K/8oZeE8F5b2dwPsCBrtTxZteYZbSbJ37CxG A mutation occurring in gametes; passed on to offspring.
jvZ5S/wVAS9v0/6+NQNPn8nLANLNYuasvgedLYuCaZkhcq72fL3G8zMLO+U1/mNt1Xe9GwKDwg6LORLyWVMFhukEdbN9TljA+saVWYom+v2GY9YIS8x1dYsyeI/0W4gks3G8zvlmVNE0zWmeW6IAulFQDtw5mwo9CWRZjliVRsR2cEQ2WyxTcM5w2QUnSDHz A gene that codes for a protein that helps cells divide normally.
S7K+6Zan22lral5PWnCG+jAoF6N7kzvDW8mf+rvTH3qRTWl6/vJVOINQr14YOXfJRidSUvgufQVWusHehti/ilEbWXVnAzAiHvmb51G0ydgldWaj4OM6UHG5ktYQY296M2CxisaxJQtm5woDCIvXorrvxe2c167NMeBvkzU2UcHeP0B2TAr0VDFuzrg3ndtX A change in the nucleotide sequence of DNA.
6KSEECbQvBLjAsW4MJiie4xQZQmT8iezd/FCU+54M8Bt4WzIJ0uV7AW8P2migzkZtfiweeFg+aHuYOneU1h0c6odXyftOUfqMlPQpwc9hLR+GN6BfAQ+qZTvWdGlQfDIYm0lbp5SVqCPwWlhRTwyz2OjgeJ3qm1k+GZhmLZNjsM5tltC9+97dhki6rt3AsSE Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.
0OB6+b/Dr83EYpdbgSO1g2WVUN90qRzm6ymfmrM3fLeFMiodt/m5GCtF7zGdCXCWJ56Cta2o3GWlhvQlS/obbEB1KS3bQtp5TGlDvGxqxoLG5jLOGaFLB5a3VcGgjCsDzo6Cwqe+UUCSoeOhFGn3I0UWOsloGqCyh+AiHcznh3n7n2Vjinl0x9ugDwhHGnA+ A cancerous tumor that spreads throughout the body.
hQ7bF3PdulKOv68/jQDBP12Eypc3pdTbtu1Icffk2HgkvgZlXmw9YrXbsl91/Ko3HqaLmsDqAla2DTFGn8XS9Lk894BkXkRmumixVckWQa84ercPgvf9DMowqya83uGAFyneqXortxQQzFOgVomE1X4mJtk/OkUwMmhSD4VJRMqkXroAqeOt7DHNhjUH1CHh A mutation that occurs in a body (nongamete) cell; not passed on to offspring.
Table
9
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Correct.
Incorrect.

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

Question 1.14

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

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TAC GGC AGC CTA CCT normal allele

Question 1.15

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TAC GGC AGC CCT ACC T mutated allele with insertion

Question 1.16

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AUG CCG UCG GGA UGG A mRNA

Question 1.17

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The mutated protein may cause cancer because if it is nonfunctional and can no longer regulate the cell cycle, cancer may develop.

Question 1.18

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Not necessarily. For cancer cells to develop, the mutation would have to result in a dysfunctional protein that somehow caused the deregulation of the cell cycle leading to uncontrolled proliferation.

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

Question 1.19

Use Infographic 10.6 to answer the following questions:

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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.

Question 1.20

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The point at which a proto-oncogene is most likely active is at the initiation of the cell cycle or G1 because a proto-oncogene promotes cell division in response to appropriate signals.

Question 1.21

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BRCA1 proteins are most likely active during the S Phase of the cell cycle because they are DNA repair proteins and it is during the S Phase that DNA replication happens.

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

Question 1.22

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An oncogene.

Question 1.23

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Mutated proto-oncogenes (or oncogenes) increase cancer risk because they are now continually “turned on” and stimulate the cell to divide uncontrollably.

Question 1.24

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Mutated tumor-suppressor genes increase cancer risk because they can no longer pause the cell cycle when there are mistakes in the DNA or cause apoptosis, so the damaged cell is allowed to continue through the cell cycle to grow and divide.

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

Question 1.25

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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.

Question 1.26

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For hereditary cancers, the DNA mutation is already present. There are still some things a person can do, however, to reduce their risk of developing cancer. They could elect to be genetically screen for specific mutations, the results of which may influence other activities in their lives (for example, a person may quit smoking if they find they have a mutation that predisposes them to lung cancer). If a deleterious mutation is confirmed (aka a mutation that has been associated with the development of cancer, like a mutation in the BRCA1 gene), the person could elect to have prophylactic surgery to remove the tissue that is likely to develop cancer.

Review Questions

Question 1.27

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2
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Question 1.28

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2
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Question 1.29

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2
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1.4 Driving Question 3

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.

Question 1.30

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 LU/yM02nlYRE6AmYkP5/HeY78u0=
A single mutation in a tumor suppressor gene associated with DNA repair.
LU/yM02nlYRE6AmYkP5/HeY78u0=
The cell is bigger and there is double the amount of organelles.
LU/yM02nlYRE6AmYkP5/HeY78u0=
There is only one copy of genomic DNA in the cell.
LU/yM02nlYRE6AmYkP5/HeY78u0=
There is only one copy of genomic DNA in the cell.
Describe its consequences LU/yM02nlYRE6AmYkP5/HeY78u0=
DNA replicates resulting in chromosome duplication.
LU/yM02nlYRE6AmYkP5/HeY78u0=
There is twice as much DNA in the cell.
LU/yM02nlYRE6AmYkP5/HeY78u0=
It is pretty similar, but there is less protein synthesis and growth happening.
LU/yM02nlYRE6AmYkP5/HeY78u0=
Correct.
Table

2
Step A Step B Step C Step D
Describe the mutation A single mutation in a tumor suppressor gene associated with DNA repair. Additional mutations in proto-oncogenes activate them into oncogenes. Additional mutations affect tumor suppressor genes associated with apoptosis signaling. Additional mutations permit tissue invasion, new blood vessel growth, and spread.
Describe its consequences The resulting protein can no longer function normally and DNA mutations are not repaired. Additional mutations begin to pile up. The cell is continually dividing without stopping for DNA repair. The mutated cell is not told to self-destruct. Cells continue to divide; the tumor is growing. The tumor contains malignant cells that invade both nearby and distant tissues.
Table
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Question 1.31

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There are many different kinds of proteins that control the cell cycle. It is unlikely that a mutation in a single gene, and thus a single protein, would cause cancer since there would be other proteins that would likely correct the mistake or, if all else fails, signal the cell to undergo apoptosis.

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

Question 1.32

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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.

Question 1.33

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I would tell my friend that just because they have a mutation that predisposes them to heart disease, it does not mean that they will absolutely develop heart disease. It means that they have a higher probability than most people of developing heart disease. So it is especially important for them to make healthy and safe life-style choices.

Review Questions

Question 1.34

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Question 1.35

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2
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Question 1.36

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2
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