Question 1

Histone modification:

Accepted Answer

Histone modification can change over time in response to environmental cues, allowing genes to be turned on or off as needed. This is known as epigenetic regulation, which involves modifications to the chromatin structure that does not involve changes to the DNA sequence. These modifications can be influenced by various factors, including diet, stress, and exposure to toxins, and can result in changes in gene expression that may be either beneficial or harmful to the organism.

Question 2

In humans and other mammals, genes in the inactivated X chromosome:

Accepted Answer

Although genes in the inactivated X chromosome are silenced by heterochromatinization, some transcription still occurs at a low level. This is important for maintaining the stability and integrity of the chromosome. Therefore, option A and C are incorrect. Option D is also incorrect, as transcription without translation would not be useful for gene expression.

Question 3

In humans and other mammals, dosage compensation is achieved by:

Accepted Answer

In mammals, including humans, dosage compensation is achieved by randomly inactivating one X chromosome in each cell of females. This process is called X chromosome inactivation or Lyonization, named after the scientist who discovered it, Mary Lyon. This ensures that both males and females have the same effective dose of X chromosome genes. The inactivated X chromosome is condensed into a structure called a Barr body, which is visible in the nucleus of the cell.

Question 4

Epigenetic mechanisms of gene regulation include:

Accepted Answer

Epigenetic mechanisms of gene regulation include modifications to the way in which DNA is packaged within chromosomes (such as changes in histone acetylation or methylation) and chemical modifications to the DNA itself (such as DNA methylation). Changes to DNA sequences (A) and repression by binding of repressor proteins (D) are not considered epigenetic mechanisms. Chromosome organization into genomes (C) is not an epigenetic mechanism but rather a characteristic of genome structure.

Question 5

Insulin is needed to regulate sugar levels in the blood. While every cell in the body contains genes for the production of insulin, it is only produced by a specialized subset of cells in the pancreas. Therefore:

Accepted Answer

Insulin is only produced by a specialized subset of cells in the pancreas, so there must be mechanisms of gene regulation that allow for insulin expression in those cells and prevent insulin expression in other cells. This is an example of tissue-specific gene regulation, which ensures that each type of cell in the body produces only the proteins it needs.

Question 6

The process by which a single primary RNA transcript is used to make multiple proteins is called:

Accepted Answer

Alternative splicing occurs when different combinations of exons are spliced together to make different mRNA molecules, which in turn can code for different proteins. This allows for multiple proteins to be made from the same primary RNA transcript.

Question 7

In RNA editing:

Accepted Answer

RNA editing involves enzymes that change the base sequence of the primary RNA transcript, leading to changes in the protein for which it codes. Option A is incorrect because spliceosomes do not change the base sequence of the RNA transcript, they only remove introns and join exons together. Option B is incorrect because different spliceosomes can generate different variants of the same RNA transcript by splicing different exons together, but not by changing the base sequence of the RNA. Option D is incorrect because microRNAs are not involved in RNA editing, they regulate gene expression by binding to RNA transcripts and preventing their translation into protein. Option E is incorrect because spliceosomes and enzymes have different functions in RNA processing, and they do not work in combination to modify the same RNA molecule.

Question 8

Gene regulation by means of epigenetic mechanisms is useful to the organism because it:

Accepted Answer

All of the choices are correct. Epigenetic mechanisms allow for changes in gene expression without altering the DNA sequence, therefore bypassing the need for new mutations. These changes can also be rapidly reversed, allowing for adaptability to changing environmental conditions. Additionally, epigenetic mechanisms can differ between the sexes, providing a means for sexual differentiation.

Question 9

Epigenetic mechanisms of gene regulation _____ inherited by daughter cells and are _____.

Accepted Answer

Epigenetic mechanisms of gene regulation can be reversible and responsive to environmental changes. They are not necessarily permanent and can be altered by external factors.

Question 10

Regulatory transcription factors:

Accepted Answer

The answer of Regulatory transcription factors:
...

Question 11

In domestic cats, the coat-color pattern known as calico is an example of:

Accepted Answer

Calico coat color in cats is an example of all the listed mechanisms: it involves gene regulation at the chromosome level, dosage compensation, epigenetic regulation, and X-inactivation. This is because the genes for coat color are located on the X chromosome, and in females (who have two X chromosomes), one of the X chromosomes is inactivated in each cell in a process known as X-inactivation or Lyonization. This leads to patches of cells expressing one allele and other patches expressing the alternate allele, resulting in the distinctive calico pattern. This process is a form of dosage compensation, is regulated at the chromosome level, and involves epigenetic changes to the inactivated X chromosome.

Question 12

A woman is heterozygous for X-linked color blindness. Considering the implications of X-inactivation, her phenotype is:

Accepted Answer

X-inactivation means that only one of the two X chromosomes in a female is active in each cell. This means that the heterozygous woman would have some cells expressing the normal color vision allele and some cells expressing the color blindness allele. However, since the normal allele is dominant, the overall phenotype would be normal color vision.

Question 13

Although lifestyle choices cannot, in general, change our genomes, they can:

Accepted Answer

Lifestyle choices can alter the physiological states of our cells, which can affect the regulation of genes after they have been transcribed. This means that lifestyle choices can increase or decrease the rate at which some genes are transcribed. However, lifestyle choices cannot change the genetic code for translation or the metabolic pathways of glycolysis, as these are determined by the sequence of our DNA.

Question 14

Gene regulation in multicellular organisms leads to differential gene expression and specialized cell functions.

Accepted Answer

This statement is true. In multicellular organisms, different cells have different functions and require different gene expressions. Gene regulation plays a crucial role in determining which genes are expressed and at what levels in different cells. This allows cells to specialize and carry out specific functions.

Question 15

Gene regulation can occur at which of the following steps in the path from DNA to protein?

Accepted Answer

Gene regulation can occur at multiple stages in the process of gene expression, including during transcription (when DNA is transcribed to RNA), during translation (when RNA is translated into protein), and after protein synthesis (post-translational modifications and regulation). This ensures that proteins are produced at the right time, in the right amount, and in the right cell type, allowing for precise control over cellular functions.

Question 16

In the type of RNA editing in which C is converted to U, which of the codons listed below could be converted to AUG?

Accepted Answer

The answer of In the type of RNA editing in...

Question 17

Which of the following questions is about gene regulation?

Accepted Answer

The answer of Which of the following questions is about...

Question 18

A cell could potentially regulate transcription by adjusting the number and kinds of:

Accepted Answer

The answer of A cell could potentially regulate transcription by...

Question 19

Methylation, acetylation, and other histone modifications are important because they are associated with:

Accepted Answer

Methylation, acetylation, and other histone modifications are associated with chromatin remodeling, which affects gene transcription. By modifying the packaging of DNA, histone modifications can make it easier or harder for transcription factors to access specific regions of the genome, ultimately turning genes on or off. CpG island methylation can also affect gene transcription, but it is not the only type of histone modification and does not explain the full scope of their importance. Histone modifications also play a role in regulating cancer genes and transposable elements, but these are not their primary functions.

Question 20

Which one of the following statements about gene regulation is INCORRECT?

Accepted Answer

Gene regulation occurs in both prokaryotes and eukaryotes, therefore statement C is incorrect. Gene regulation can occur at multiple levels including the chromosomal, transcriptional, translational, and post-translational levels.

Quiz 19: Genetic and Epigenetic Regulation