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Chapter 18 Questions Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then

A

the amino acid acts as a corepressor

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2
Q

Muscle cells differ from nerve cells mainly because they

A

express different genes

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3
Q

The functioning of enhancers is an example of

A

transcriptional control of gene expression

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4
Q

Cell differentiation always involves

A

the production of tissue-specific proteins, such as muscle actin

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5
Q

Which of the following is an example of post-transcriptional control of gene expression?

A

the removal of introns and alternative splicing of exons

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6
Q

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

A

continuous transcription of the operon’s genes

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7
Q

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene

A

normally leads to formation of head structures

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8
Q

Which of the following statements about the DNA in one of your brain cells is true?

A

it is the same as the DNA in one of your heart cells

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9
Q

Within a cell, the amount of protein made using a given mRNA molecule depends partly on

A

the rate at which the mRNA is degraded

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10
Q

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cels?

A

proto-oncogenes normally help regulate cell division.

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11
Q

Which of the following would be most likely to lead to cancer?

A

amplification of a proto-oncogene and inactivation of a tumor-suppressor gene

-Excess copies of the proto-oncogene could stimulate cell division abnormally, and the inactivation of a tumor-suppressor gene would eliminate a brake on cell division.

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12
Q

All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs?

A

Proto-oncogenes are necessary for the normal control of cell growth and division.

-Proto-oncogenes can become oncogenes when a mutation or other genetic change increases the activity of the encoded protein.

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13
Q

Which of these are carcinogens?

A

cigarette smoke
fat
testosterone
UV light

(all of these substances can cause cancer)

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14
Q

_____ is a carcinogen that promotes colon cancer.

A

fat

-A diet high in fat increases the risk of both colon and breast cancer.

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15
Q

A cancer cell _____.

A

does not respond to the chemical signals that control cell division

-Cancer is a set of diseases in which cells escape from the control mechanisms that normally limit their rate of division.

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16
Q

In the human genome, oncogenes _____.

A

stimulate cell division

-Oncogenes are cancer-causing genes; repair of DNA damage would help prevent cancer.

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17
Q

Most human cancers are _____.

A

caused by the accumulation of somatic mutations

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18
Q

What gene has been called the “guardian angel of the genome?”

A

the p53 gene

-The p53 gene can activate several genes involved in DNA repair, halting of the cell cycle, or initiation of apoptosis.

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19
Q

What two genes are often mutated in colon cancer?

A

ras and p53

-ras, an oncogene, and p53, a tumor-suppressor gene, are often found to be mutated in colon cancers.

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20
Q

Why is cancer more prevalent in older people?

A

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

-Older people have simply had more cell divisions, more exposure to environmental carcinogens, and so on. Chance dictates that they have had more opportunities for mutations to occur.

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21
Q

In what way can cancer be hereditary?

A

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

-Because most cancers involve several mutations, a person who inherits one or more of these mutations will be more susceptible to cancer, but will not necessarily develop it,

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22
Q

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

A

tumor-suppressor genes

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23
Q

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

A

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.

-Although it is understood that p53 plays a critical role in the regulation of normal cells and suppressing tumor development, the precise ways that it carries out this role is not fully understood.

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24
Q

The control of gene expression is more complex in multicellular eukaryotes than in prokaryotes because _____.

A

in a multicellular eukaryote, different cells are specialized for different functions

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25
Q

In some cases DNA methylation and histone deacetylation combine to _____.

A

silence certain genes

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26
Q

In eukaryotes, DNA packing seems to affect gene expression primarily by _____

A

controlling access to DNA

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27
Q

A scientist clones a regulatory gene that is involved in controlling the expression of other genes, and discovers that the regulatory gene encodes a histone deacetylase enzyme. It is likely that this enzyme regulates gene expression by _____.

A

causing tighter packing of the chromatin at the target gene, thereby inhibiting transcription

28
Q

In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called a(n) _____.

A

enhancer

-Enhancers are sites within the DNA where activators bind, increasing the rate of transcription.

29
Q

Enhancers _____.

A
  • may be located upstream or downstream from the genes they regulate
  • may be located thousands of base pairs away from the promoter
  • increase the rate of transcription
  • are found in eukaryotic genomes
30
Q

Dioxin, produced as a by-product of various industrial chemical processes, is suspected of causing cancer and birth defects in animals and humans. It apparently acts by entering cells and binding to specific proteins, which then enter the nucleus and alter the pattern of gene expression. Therefore, dioxin acts by mimicking the action of _____.

A

steroid hormones

-Steroid hormones enter cells, bind to specific receptors, and enter the nucleus to affect transcription.

31
Q

Post-transcriptional controls _____.

A
  • may regulate the rate at which a molecule is translated
  • can include translational controls
  • can affect mRNA stability
  • can regulate mRNA splicing
32
Q

Which of the following is a means of controlling eukaryotic gene expression?

A
  • methylation of DNA
  • mRNA processing
  • DNA packing
  • transcriptional regulation
33
Q

What is the evolutionary significance of alternative RNA splicing?

A

It expands the number of proteins that can be coded for by one gene, increasing an organism’s ability to produce novel proteins.

34
Q

What is the role of proteasomes?

A

They are giant protein complexes that recognize ubiquitin and degrade the tagged proteins.

-Mutations that make cell cycle proteins impervious to proteasome degradation can lead to cancer.

35
Q

What determines how long a particular mRNA molecule will persist in a eukaryotic cell?

A

nucleotide sequences in the poly-A tail

-Nucleotide sequences in the untranslated region at the 3’ end of the molecule seem to be crucial in determining how long-lived a particular mRNA is.

36
Q

The expression of a gene located in a tightly coiled region of DNA can be promoted by _____.

A

histone acetylation

37
Q

Which of the following statements is NOT associated with epigenetic inheritance?

A

chemical mutagens

38
Q

A high rate of gene transcription in eukaryotic cells is usually dependent on _____.

A
  • specific binding of activator molecules to enhancers

- protein-protein interactions that are promoted by the activation domains of activator proteins

39
Q

Which of the following best depicts coordinate control of genes in eukaryotes?

A
  • Although a group of genes involved in a related metabolic process are typically scattered over different chromosomes, their co-activation is achieved by every gene of the group sharing a specific combination of control elements and activator molecules that bind to them.
  • Although a group of genes involved in a related metabolic process are typically scattered over different chromosomes, coordinated expression of this group is enhanced by the congregation of loops from different chromosomes in a specific site of the nucleus to form a transcription factory.
40
Q

Although the number of genes in the human genome is surprisingly low compared to less complex organisms, the number of possible products from those genes is greatly amplified by _____.

A

alternate arrangements of exons from a primary transcript

41
Q

Which of the following best describes the makeup of the human genome?

A

Genes for noncoding RNA make up the majority of meaningful genetic information in the human genome.

42
Q

The discovery of many noncoding RNAs is causing scientists to revise the long-held view that _____.

A
  • only DNA that codes for protein, tRNA, and rRNA is transcribed
  • there are only three types of RNA—tRNA, rRNA, and mRNA
  • the vast majority of the human genome consists of “junk” DNA
  • all genes code for proteins
43
Q

MicroRNAs and small interfering RNAs both function similarly in “silencing” genes. What are two ways in which they may act?

A

degrade mRNA and bind to complementary mRNA sequences to prevent translation

-miRNAs and siRNAs act in both of these ways to prevent a transcribed gene from being translated into protein. In addition to their normal roles in cells, researchers see these RNAs as useful tools in studying the function of genes by being able to silence them.

44
Q

It is hypothesized that an increase in the number and diversity of noncoding RNA (ncRNA) in the genomes of species has driven the evolution of morphological complexity by way of their influence on gene regulation. Which of the following accurately describes our current understanding of the role that ncRNA is thought to play in gene regulation?

A
  • Some ncRNA can promote the formation of heterochromatin, thereby blocking the expression of genes in the tightly coiled region.
  • ncRNAs can fine-tune translation by binding with mRNA via complementary base pairing and promote the degradation of the mRNA strand or block its translation.
  • Whereas some ncRNA block the transcription and translation of some genes, others have been observed to activate gene expression.
  • ncRNAs can re-establish proper patterns of DNA methylation in the genome during gamete formation.
45
Q

It is hypothesized that an increase in the number and diversity of noncoding RNA (ncRNA) in the genomes of species has driven the evolution of morphological complexity by way of their influence on gene regulation. Which of the following accurately describes our current understanding of the role that ncRNA is thought to play in gene regulation?

A
  • Some ncRNA can promote the formation of heterochromatin, thereby blocking the expression of genes in the tightly coiled region.
  • ncRNAs can fine-tune translation by binding with mRNA via complementary base pairing and promote the degradation of the mRNA strand or block its translation.
  • Whereas some ncRNA block the transcription and translation of some genes, others have been observed to activate gene expression.
  • ncRNAs can re-establish proper patterns of DNA methylation in the genome during gamete formation.
46
Q

MicroRNAs and small interfering RNAs both function similarly in “silencing” genes. What are two ways in which they may act?

A

degrade mRNA and bind to complementary mRNA sequences to prevent translation

-miRNAs and siRNAs act in both of these ways to prevent a transcribed gene from being translated into protein. In addition to their normal roles in cells, researchers see these RNAs as useful tools in studying the function of genes by being able to silence them.

47
Q

The discovery of many noncoding RNAs is causing scientists to revise the long-held view that _____.

A
  • only DNA that codes for protein, tRNA, and rRNA is transcribed
  • there are only three types of RNA—tRNA, rRNA, and mRNA
  • the vast majority of the human genome consists of “junk” DNA
  • all genes code for proteins
48
Q

Which of the following best describes the makeup of the human genome?

A

Genes for noncoding RNA make up the majority of meaningful genetic information in the human genome.

49
Q

Although the number of genes in the human genome is surprisingly low compared to less complex organisms, the number of possible products from those genes is greatly amplified by _____.

A

alternate arrangements of exons from a primary transcript

50
Q

Which of the following best depicts coordinate control of genes in eukaryotes?

A
  • Although a group of genes involved in a related metabolic process are typically scattered over different chromosomes, their co-activation is achieved by every gene of the group sharing a specific combination of control elements and activator molecules that bind to them.
  • Although a group of genes involved in a related metabolic process are typically scattered over different chromosomes, coordinated expression of this group is enhanced by the congregation of loops from different chromosomes in a specific site of the nucleus to form a transcription factory.
51
Q

A high rate of gene transcription in eukaryotic cells is usually dependent on _____.

A
  • specific binding of activator molecules to enhancers

- protein-protein interactions that are promoted by the activation domains of activator proteins

52
Q

Which of the following statements is NOT associated with epigenetic inheritance?

A

chemical mutagens

53
Q

The expression of a gene located in a tightly coiled region of DNA can be promoted by _____.

A

histone acetylation

54
Q

What determines how long a particular mRNA molecule will persist in a eukaryotic cell?

A

nucleotide sequences in the poly-A tail

-Nucleotide sequences in the untranslated region at the 3’ end of the molecule seem to be crucial in determining how long-lived a particular mRNA is.

55
Q

What is the role of proteasomes?

A

They are giant protein complexes that recognize ubiquitin and degrade the tagged proteins.

-Mutations that make cell cycle proteins impervious to proteasome degradation can lead to cancer.

56
Q

What is the evolutionary significance of alternative RNA splicing?

A

It expands the number of proteins that can be coded for by one gene, increasing an organism’s ability to produce novel proteins.

57
Q

Which of the following is a means of controlling eukaryotic gene expression?

A
  • methylation of DNA
  • mRNA processing
  • DNA packing
  • transcriptional regulation
58
Q

Post-transcriptional controls _____.

A
  • may regulate the rate at which a molecule is translated
  • can include translational controls
  • can affect mRNA stability
  • can regulate mRNA splicing
59
Q

Dioxin, produced as a by-product of various industrial chemical processes, is suspected of causing cancer and birth defects in animals and humans. It apparently acts by entering cells and binding to specific proteins, which then enter the nucleus and alter the pattern of gene expression. Therefore, dioxin acts by mimicking the action of _____.

A

steroid hormones

-Steroid hormones enter cells, bind to specific receptors, and enter the nucleus to affect transcription.

60
Q

Enhancers _____.

A
  • may be located upstream or downstream from the genes they regulate
  • may be located thousands of base pairs away from the promoter
  • increase the rate of transcription
  • are found in eukaryotic genomes
61
Q

In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called a(n) _____.

A

enhancer

-Enhancers are sites within the DNA where activators bind, increasing the rate of transcription.

62
Q

A scientist clones a regulatory gene that is involved in controlling the expression of other genes, and discovers that the regulatory gene encodes a histone deacetylase enzyme. It is likely that this enzyme regulates gene expression by _____.

A

causing tighter packing of the chromatin at the target gene, thereby inhibiting transcription

63
Q

In eukaryotes, DNA packing seems to affect gene expression primarily by _____

A

controlling access to DNA

64
Q

In some cases DNA methylation and histone deacetylation combine to _____.

A

silence certain genes

65
Q

The control of gene expression is more complex in multicellular eukaryotes than in prokaryotes because _____.

A

in a multicellular eukaryote, different cells are specialized for different functions

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