Question 1

If a cell were unable to produce histone proteins, which of the following would be a likely effect?
A) There would be an increase in the amount of "satellite" DNA produced during centrifugation.
B) The cell's DNA couldn't be packed into its nucleus.
C) Spindle fibers would not form during prophase.
D) Amplification of other genes would compensate for the lack of histones.

Accepted Answer

Histones are key proteins that DNA molecules wrap around to form nucleosomes, which help DNA to be compacted into a compact structure that will fit inside the cell nucleus. Therefore, if a cell is unable to produce histone proteins, it wouldn't be able to pack its DNA tightly and efficiently into its nucleus.

Question 2

Which of the following statements describes a eukaryotic chromosome?
A) a single strand of DNA
B) a series of nucleosomes wrapped around two DNA molecules
C) a chromosome with different numbers of genes in different cell types of an organism
D) a single linear molecule of double-stranded DNA plus proteins

Accepted Answer

Eukaryotic chromosomes are typically large linear molecules of double-stranded DNA that are associated with proteins, such as histones, that help to package and organize the DNA. These protein-DNA complexes are often referred to as chromatin. Eukaryotes can have multiple chromosomes, and each chromosome contains many genes that help to direct cellular activities.

Question 3

Which of the following is most critical for the association between histones and DNA?
A) Histones are small proteins.
B) Histones are highly conserved (that is, histones are very similar in every eukaryote).
C) Histones are synthesized in the cytoplasm.
D) There are at least five different histone proteins in every eukaryote.
E) Histones are positively charged.

Accepted Answer

Histones are positively charged proteins, while DNA is negatively charged due to its phosphate groups. This electrostatic attraction between positively charged histones and negatively charged DNA is critical for the association between histones and DNA in the formation of nucleosomes.

Question 4

Several of the different globin genes are expressed in humans but at different times in development. What mechanism could allow for this?
A) exon shuffling
B) intron activation
C) pseudogene activation
D) differential translation of mRNAs
E) differential gene regulation over time

Accepted Answer

Differential gene regulation over time is the most likely mechanism for allowing different globin genes to be expressed at different times during development. This could occur through the activation of regulatory elements that control the timing and level of expression of each gene. Other mechanisms, such as exon shuffling or intron activation, would not explain the temporal regulation of globin gene expression. Pseudogene activation is also an unlikely mechanism, as pseudogenes are generally non-functional and do not contribute to gene expression. Differential translation of mRNAs could contribute to differences in protein abundance, but would not explain the specific timing of globin gene expression during development.

Question 5

Which of the following statements about the DNA in one of your brain cells is TRUE?
A) Most of the DNA codes for protein.
B) All of the genes of the genome are likely to be transcribed.
C) Each gene lies immediately adjacent to an enhancer.
D) Many related genes are transcribed from a single promoter.
E) It is the same as the DNA in one of your heart cells.

Accepted Answer

The DNA in all cells of an individual's body, whether they are brain cells or heart cells, is essentially the same. The differences in cell function are due to different patterns of gene expression rather than differences in the DNA sequence itself.

Question 6

Which of the following allows more than one type of protein to be produced from one gene?
A) alternative forms of chromatin remodeling
B) alternative forms of RNA splicing
C) alternative forms of nucleosomes
D) control of the frequency of translation initiation

Accepted Answer

Alternative forms of RNA splicing allow for different combinations of exons to be included or skipped during mRNA processing, resulting in the production of multiple types of proteins from a single gene. The other options refer to chromatin structure or translational control, which can regulate gene expression but do not directly impact the production of different protein variants.

Question 7

Why do histones bind tightly to DNA?
A) Histones are positively charged, and DNA is negatively charged.
B) Histones are negatively charged, and DNA is positively charged.
C) Both histones and DNA are strongly hydrophobic.
D) Histones are covalently linked to the DNA.
E) Histones are highly hydrophobic, and DNA is hydrophilic.

Accepted Answer

Histones are positively charged due to their high content of basic amino acids (arginine and lysine), while DNA is negatively charged due to its phosphate backbone. This electrostatic interaction between the positively charged histones and negatively charged DNA is what causes the tight binding between them.

Question 8

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is NOT coding for proteins?
A) most of the DNA serving as origins of DNA replication
B) DNA that consists of histone coding sequences
C) DNA that is translated directly without being transcribed
D) non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
E) non-protein-coding DNA that serves as binding sites for reverse transcriptase

Accepted Answer

Non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function can account for much of the DNA that is not coding for proteins. These small RNAs play important roles in gene regulation, chromatin remodeling, and other cellular processes. The other options, such as origins of DNA replication, histone coding sequences, and binding sites for reverse transcriptase, do not account for a significant amount of non-coding DNA. DNA that is translated directly without being transcribed is a hypothetical scenario and does not occur in cells.

Question 9

The predominant mechanism driving cellular differentiation is the difference in gene ________.
A) expression
B) sequences
C) order
D) replication

Accepted Answer

Cellular differentiation refers to the process through which cells develop into specific cell types with unique functions. Gene expression is the process by which the information encoded in a gene is used to direct cellular activities, such as the synthesis of proteins. Therefore, the difference in gene expression, rather than gene sequence or order or replication, is the predominant mechanism driving cellular differentiation.

Question 10

If you were to observe the activity of methylated DNA, you would expect it to ________.
A) be replicating nearly continuously
B) be unwinding in preparation for protein synthesis
C) have turned off or slowed down the process of transcription
D) be very actively transcribed and translated
E) induce protein synthesis by not allowing repressors to bind to it

Accepted Answer

Methylation of DNA is a type of epigenetic modification that typically results in the inhibition or silencing of gene expression. Methylation can physically obstruct transcription factors and prevent them from binding to DNA, which can lead to reduced transcription of the associated gene. Therefore, if you were to observe the activity of methylated DNA, you would expect it to have turned off or slowed down the process of transcription.

Question 11

Two potential devices that eukaryotic cells use to regulate transcription are ________.
A) DNA methylation and histone amplification
B) DNA amplification and histone methylation
C) DNA acetylation and methylation
D) DNA methylation and histone modification
E) histone amplification and DNA acetylation

Accepted Answer

Eukaryotic cells can use DNA methylation and histone modification as potential devices to regulate transcription. DNA methylation involves the addition of a methyl group to cytosine bases in DNA, which can prevent transcription factors from binding to the promoter region of a gene. Histone modification involves the addition or removal of chemical groups from histone proteins, which can alter the accessibility of DNA to transcription factors and RNA polymerase.

Question 12

Cell differentiation always involves ________.
A) the production of tissue-specific proteins, such as muscle actin
B) the movement of cells
C) the transcription of the myoD gene
D) the selective loss of certain genes from the genome
E) the cell's sensitivity to environmental cues, such as light or heat

Accepted Answer

Cell differentiation involves the production of tissue-specific proteins, such as muscle actin, which allow cells to carry out specialized functions and form specific tissues and organs. While movement and gene regulation (such as transcription of the myoD gene) may be involved in cell differentiation, they are not always necessary or sufficient for the process. The selective loss of certain genes from the genome is not a hallmark of differentiation, and while environmental cues may influence cell behavior, they do not define the process of differentiation itself.

Question 13

Use this information to answer the question(s) below.
-In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?
A) increased chromatin condensation
B) decreased chromatin condensation
C) activation of histone tails for enzymatic function
D) decreased binding of transcription factors
E) inactivation of the selected genes

Accepted Answer

Acetylation of histone tails is known to result in decreased chromatin condensation, which leads to increased accessibility of the DNA for transcription.

Question 14

Cloning of plants from cuttings demonstrates that ________.
A) an individual plant cell cannot de-differentiate and then re-differentiate
B) differentiated plant cells may contain embryonic mRNAs
C) plants lose genetic information in the differentiation process
D) mature plant cells retain the full genetic information needed to carry out the developmental processes to produce a new individual plant

Accepted Answer

Cloning of plants from cuttings involves taking a portion of a mature plant and forcing it to regenerate a new individual that is identical to the parent plant. This process is only possible because mature plant cells retain the full genetic information needed to carry out the developmental processes to produce a new individual plant. This demonstrates that differentiation of plant cells does not cause a loss of genetic information.

Question 15

Which of the following statements is TRUE of histones?
A) Each nucleosome consists of two molecules of histone H1.
B) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
C) The carboxyl end of each histone extends outward from the nucleosome and is called a "histone tail."
D) Histones are found in mammals but not in other animals or in plants or fungi.

Accepted Answer

Histone H1 is known as the linker histone, which is not part of the core nucleosome structure but is involved in the higher-order structure of chromatin by binding to the DNA between nucleosomes and helping to compact the chromatin structure.

Question 16

Mammals have a family between 500 and 1000 genes that encode receptor proteins on the surface of odor-receptor neurons. If all mammals have these genes, why do some mammals have a better sense of smell than others do?
A) Some of the genes actively transcribing receptor proteins in some species are completely absent in other species.
B) Some of the genes may have been mutated and rendered inactive in some species but not in others.
C) Some species, particularly humans, rely much less on odor detection for survival; thus, the genes have mutated to encode proteins that aid in other senses, such as sight.
D) Some species of mammals have a larger set of "basic odors" than other species.

Accepted Answer

Mutated or inactive genes can result in a diminished sense of smell in some species even if they possess the same number of receptor protein genes as other mammals.

Question 17

Muscle cells differ from nerve cells mainly because they ________.
A) express different genes
B) contain different genes
C) use different genetic codes
D) have unique ribosomes
E) have different chromosomes

Accepted Answer

Muscle cells and nerve cells have different functions, so they require different gene expression to carry out their respective tasks. However, both cell types contain the same genes, with the exception of certain genes required for their specific functions. Therefore, the best answer is A, as it correctly states that muscle cells and nerve cells express different genes to carry out their different functions.

Question 18

DNA methylation and histone acetylation are examples of ________.
A) genetic mutation
B) chromosomal rearrangements
C) karyotypes
D) epigenetic phenomena
E) translocation

Accepted Answer

DNA methylation and histone acetylation are epigenetic phenomena, which refer to heritable changes in gene expression that do not involve changes in the DNA sequence itself.

Question 19

Which method is utilized by eukaryotes to control their gene expression that is NOT used in bacteria?
A) control of chromatin remodeling
B) control of RNA splicing
C) transcriptional control
D) control of both RNA splicing and chromatin remodeling
E) control of chromatin remodeling, RNA splicing, and transcription

Accepted Answer

Control of both RNA splicing and chromatin remodeling are utilized by eukaryotes to control their gene expression but not by bacteria. Bacteria typically regulate gene expression at the transcriptional level, whereas eukaryotes have additional layers of control such as RNA splicing and chromatin remodeling.

Question 20

In a nucleosome, the DNA is wrapped around ________.
A) polymerase molecules
B) ribosomes
C) histones
D) a thymine dimer
E) satellite DNA

Accepted Answer

The DNA in a nucleosome is wrapped around histones, which are proteins that help pack the DNA into a compact structure.

Quiz 19: Control of Gene Expression in Eukaryotes

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

Which of the following statements describes a eukaryotic chromosome?

Which of the following is most critical for the association between histones and DNA?

Several of the different globin genes are expressed in humans but at different times in development. What mechanism could allow for this?

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

Which of the following allows more than one type of protein to be produced from one gene?

Why do histones bind tightly to DNA?

The predominant mechanism driving cellular differentiation is the difference in gene ________.

If you were to observe the activity of methylated DNA, you would expect it to ________.

Two potential devices that eukaryotic cells use to regulate transcription are ________.

Cell differentiation always involves ________.

Use this information to answer the question(s) below. -In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?

Cloning of plants from cuttings demonstrates that ________.

Which of the following statements is TRUE of histones?

Mammals have a family between 500 and 1000 genes that encode receptor proteins on the surface of odor-receptor neurons. If all mammals have these genes, why do some mammals have a better sense of smell than others do?

Muscle cells differ from nerve cells mainly because they ________.

DNA methylation and histone acetylation are examples of ________.

Which method is utilized by eukaryotes to control their gene expression that is NOT used in bacteria?

In a nucleosome, the DNA is wrapped around ________.