11. Cell Division

Cancer

Soils, water, and the atmosphere are major components of the abiotic (nonliving) environment. Describe how green plants affect the abiotic environment in ways that are advantageous to humans.

Short Video: Tumor Growth

Animation: The Human Life Cycle

 Cancer is caused by viruses, and older people are more susceptible to viral infections. 

 No. Viruses are responsible for about 15% of human cancer cases. 

 Cancer lies dormant for many years before causing problems. 

 No. Although some cancers develop slowly, many can be very aggressive and develop quickly. 

 Most cancers are inherited as a recessive allele, so it takes time for the allele to be expressed. 

 Cancer involves changes in gene expression, and it takes many years for gene expression to change. 

 No. Gene expression can change almost instantaneously. 

 Cancer involves an accumulation of mutations, and older people have had more time to accumulate mutations in their DNA. 

If you roll the dice more times, are you more or less likely to roll snake eyes?

Why is cancer more prevalent in older people?

Types of Genes Regulating Cell Growth

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
a. disruption of mitotic spindle formation.
b. suppression of cyclin production.
c. myosin denaturation and inhibition of cleavage furrow formation.
d.inhibition of DNA synthesis.

 inherited from one parent, like an autosomal dominant allele 

 inherited from both parents, like an autosomal recessive allele 

 No. Radiation is one possible cause of cancer-causing mutations, but it is not the primary one. 

 caused by the accumulation of somatic mutations 

What is at the root of cancer?

Most human cancers are __________.

Oncogenes and Tumor Suppressor Genes - Tumor Genetics

The mycelial growth habit leads to a body with a high surface-area-to-volume ratio. Why is this important?
a. Mycelia have a large surface area for absorption.
b. The hyphae that make up mycelia are long, thin tubes.
c. Most hyphae are broken up into compartments by walls called septa, although some exist as single, gigantic cells.
d. Hyphae can infiltrate living or dead tissues.

 No. This is not a characteristic of a cancer. 

 No. Oncogenes promote cancer, and cancerous cells generally show decreased cell-cell adhesion. 

 No. Oncogenes are cancer-causing genes; repair of DNA damage would help prevent cancer. 

Review the terminology for the different types of genes involved in cancer.

In the human genome, oncogenes __________.

 The cancer cells produce molecules that inhibit the growth factors required for cell division. 

 No. If they were inhibited, cell division could not occur. 

 The cancer cells exhibit anchorage dependence. 

 No. Cancer cells are characterized by the lack of anchorage dependence. 

The cancer cells spend the majority of their time in the G0 phase.

No. Cells in the G0 phase have assumed a nondividing state.

 All of the listed responses are correct. 

 No. Only one of the choices is correct. 

 The cancer cells do not exhibit density-dependent inhibition. 

Consider how cancer cells differ from noncancerous cells.

Which of the following hypotheses is best supported by observing cancer cells in a culture?

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?
a. Proto-oncogenes first arose from viral infections.
b. Proto-oncogenes are mutant versions of normal genes.
c. Proto-oncogenes are genetic “junk.”
d. Proto-oncogenes normally help regulate cell division.

Animation: Causes of Cancer

They stimulate normal cell growth and division.

Which of the following processes do normal proto-oncogenes typically exhibit?a) &nbsp; &nbsp;They normally suppress tumor growth.b) &nbsp; &nbsp;They enhance tumor growth.c) &nbsp; &nbsp;They stimulate normal cell growth and division.d) &nbsp; &nbsp;They are underexpressed in cancer cells.

 No. They are probably tumor-suppressor genes. 

 No. They are normal parts of the human genome. 

How are they inherited?

The BRCA1 and BRCA2 genes are thought to be what type of genes?

 Benign tumors arise by transformation; malignant tumors do not. 

 No. Both types of tumors arise when a single cell undergoes transformation. 

 Cells of benign tumors metastasize; those of malignant tumors do not. 

 Benign tumors will not kill you; malignant tumors will. 

 No. Consider an untreated or inoperable benign brain tumor. 

 Benign tumors do not arise by transformation; malignant tumors do. 

 Cells of benign tumors do not metastasize; those of malignant tumors do. 

A person with a malignant tumor is said to have cancer.

What is the difference between a benign tumor and a malignant tumor?

BioFlix: Meiosis Interphase

The cancer gene we all have - Michael Windelspecht

No. The p21 gene can halt the cell cycle, but it is not the guardian angel.

No. The BRCA1 gene is involved in the development of breast cancer.

No. The ras gene is a proto-oncogene. When it is mutated, it stimulates cell division.

No. The myoD gene is a master regulatory gene involved in the differentiation of muscle cells.

This gene has multiple effects.

What gene has been called the "guardian angel of the genome"?

One difference between cancer cells and normal cells is that cancer cells
a. are unable to synthesize DNA.
b. are arrested at the S phase of the cell cycle.
c. continue to divide even when they are tightly packed together.
d. cannot function properly because they are affected by density-dependent inhibition.

Tumor Suppressor Genes: What is Cancer? Video Series

No. myoD is involved in muscle cell differentiation.

 No. These both function primarily as tumor-suppressor genes. Full cancer development usually involves both oncogenes and tumor-suppressor genes. 

 No. These genes are primarily involved in breast cancer development. 

No. Although APC is implicated in many inherited colon cancers, myoD is involved in the differentiation of muscle cells.

Think about what it takes to really disturb the cell cycle.

What two genes are often mutated in colon cancer?

GCSE Biology - What is Cancer? 'Benign' and 'Malignant' Tumours Explained  #43

How do cancer cells behave differently from healthy ones? - George Zaidan

Describe three ways that cancer cells differ from normal cells.

 A person can inherit cancer cells from one of his/her parents. 

 No. A person does not inherit cells from his/her parents. A person inherits chromosomes. 

 All of the mutations necessary for full cancer development can be inherited, giving a person a predisposition to developing cancer. 

 No. It is unlikely that a person whose genome contained all the mutations necessary for full cancer development would live long enough to reproduce. 

 Proto-oncogenes can be inherited, giving the person a predisposition to developing cancer. 

 No. Proto-oncogenes are always inherited. For the most part, proto-oncogenes are normal genes that code for growth factors. 

 Tumor-suppressor genes can be inherited, giving the person a predisposition to developing cancer. 

 No. Tumor-suppressor genes are always inherited, but they help prevent cancer. 

 One or two of several mutations necessary for full cancer development can be inherited, giving a person a predisposition to developing cancer. 

Remember that cancer usually requires several mutations for full development.

In what way can cancer be hereditary?

When activated by signals in the cell, Protein X can stop cells from growing and dividing into new cells. What type of gene codes for Protein X?a) Oncogene.b) Tumor-suppressor gene.c) Protein kinase gene.d) Protein Vesicle gene.e) Proto-oncogene.

 Mutations in a single gene cannot significantly increase susceptibility to cancer. 

No. Mutations in a single gene can significantly increase the chances of developing some types of cancer. As an example, inheriting one mutant BRCA1 allele exposes a woman to a 60% probability of developing breast cancer before the age of 50, compared with only a 2% probability for an individual homozygous for the normal allele.

 Study results suggest that mutations in genes that are transcribed into ncRNA do not likely contribute to cancer development. 

 No. Studies suggest that mutations in genes for ncRNA, such as miRNA, can cause errors in gene regulation that lead to uncontrolled cell growth. 

We now understand that all cancers result from some mutation in the p53 gene.

No. Although it is understood that p53 protein plays a critical role in the regulation of normal cells and suppressing tumor development, the loss of p53 function is not associated with all tumors.

 Nearly all cancers are caused by the multistep accumulation of mutations over the life span of the individual. 

 No. Individuals can inherit mutations that increase their chances of developing cancer. Also, tumor viruses, such as papillomaviruses, are responsible for about 15% of human cancer cases. 

 In order for a cell to become fully cancerous, it typically must have at least one active oncogene and the mutation or loss of several tumor-suppressor genes. 

Is cancer development dependent on one or multiple factors coming into play?

Which of the following accurately characterizes our current understanding of cancer development?

Oncogenes: What is Cancer? Video Series

Malignant tumors do not spread to other sites.

Benign tumors have not lost growth control.

Benign tumors have not spread to other sites.

Malignant tumors have not lost growth or control.

The difference between benign and malignant tumors is:a) Malignant tumors do not spread to other sites.b) Benign tumors have not lost growth control.c) &nbsp;Benign tumors have not spread to other sites.d) &nbsp;Malignant tumors have not lost growth or control.

 is typically more than 10 times larger than a normal cell 

 No. A cancer cell does contain a nucleus. 

 requires less nutrients than a normal cell 

 No. Cancer cells are dividing cells and, as such, require lots of nutrients. 

 No. Only one of the listed responses is correct. 

 does not respond to the chemical signals that control cell division 

Consider what a cancer is and what it does.

A cancer cell __________.

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