bio chapter 10

MALIGNANT TUMOR

A cancerous tumor that spreads throughout the body.

MUTATION

A change in the nucleotide sequence of DNA.

mutation

A change in the nucleotide sequence of DNA.

PROTO-ONCOGENE

A gene that codes for a protein that helps cells divide normally.

TUMOR SUPPRESSOR GENE

A gene that codes for proteins that monitor and check cell cycle progression. When these genes mutate, tumor suppressor proteins lose normal function.

ONCOGENE

A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually.

GERM-LINE MUTATION

A mutation occurring in gametes; passed on to offspring.

germ-line mutation

A mutation occurring in gametes; passed on to offspring.

SOMATIC MUTATION

A mutation that occurs in a body (nongamete) cell; not passed on to offspring.

somatic mutation

A mutation that occurs in a body (nongamete) cell; not passed on to offspring.

BENIGN TUMOR

A noncancerous tumor that will not spread throughout the body.

How would you explain to someone with a limited understanding of genetics the relationship between mutations and alleles?

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

CARCINOGEN

Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.

MUTAGEN

Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.

Mutagen

Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.

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).

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.

Why do mutated proto-oncogenes increase cancer risk?

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

Why do mutated tumor-suppressor genes increase cancer risk?

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.

In general, will any mutation that produces a dysfunctional protein increase cancer risk? Explain.

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 the DNA sequences shown for the normal and mutated BRCA1 alleles. Based on your understanding of transcription and translation, how different would proteins produced by these two alleles be?

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.

If a mutation that occurs during DNA replication is not corrected as a sperm cell is generated, is the new allele passed on to the next generation?

The new allele would be passed on to the next generation.

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 why a mutation in a single gene (either a proto-oncogene or a tumor suppressor gene) is unlikely to cause cancer on its own.

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.

What are some measures a person can take to reduce their risk of hereditary cancers? How do these measures reduce cancer risk?

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.

Why does a person with an inherited mutation in a proto-oncogene more likely to develop cancer at a younger age?

They require fewer additional mutations to develop cancer.

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

True

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

false

True or False. Avoiding all mutagens and carcinogens will guarantee a cancer-free life.

false

True or False: A person who has a mutation in their BRCA2 gene will develop breast cancer at some point in their life.

false

Mutations in DNA can be caused by:

smoking cigarettes, heredity, uv light from tanning bed, char

True or False: A person with a hereditary mutation in a tumor suppressor gene would especially benefit from reducing their risk of cancer from environmental factors.

true