Bio 203 Ch. 18 Practice Test Questions

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

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.

Why is cancer more prevalent in older people?

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

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

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

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

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.

Which of the following statements about inhibition is/are true?

It allows a cell to adapt quickly to fluctuations in the availability of important substances. It is common in anabolic pathways. If the end product accumulates in the cell, the whole pathway is shut down. The end product of the metabolic pathway controls the activity of the first enzyme in the pathway.

What is the evolutionary significance of alternative RNA splicing?

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

In what way can cancer be hereditary?

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

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 represents our current understanding of the role that ncRNA is thought to play in gene regulation?

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. 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.

Instead of developing a head and a tail, an abnormal Drosophila embryo develops two tails. This is most likely due to __________.

a mutation in a maternal effect gene

You have inserted the gene for human growth factor into the E. coli lactose operon, replacing the structural genes with the gene for human growth factor. What substance must you add to your culture of bacteria to cause them to produce human growth factor for you?

allolactose

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 __________.

alternate arrangements of exons from a primary transcript

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

histone acetylation

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

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

Cells can influence each other's development by a process known as __________

induction

E. coli, the bacterium may need to synthesize tryptophan, or its hosts a human, may supply all the tryptophan it needs. Why do both bacteria and humans need tryptophan?

its is one of the 20 amino acids used by all organisms to synthesize proteins

Cell differentiation is first observable when __________.

mRNAs for tissue-specific proteins appear in a cell

Which of the following is/are involved in controlling eukaryotic gene expression?

methylation of DNA transcriptional regulation DNA packing mRNA processing

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

promote the degradation of mRNA and bind to complementary mRNA sequences to prevent translation

What two genes are often mutated in colon cancer?

ras and p53

In general, operons that encode the enzymes of a biosynthetic (anabolic) pathway (such as the trp operon) are __________, and those encoding the enzymes of a catabolic pathway (such as the lac operon) are __________.

repressible ... inducible

In some cases, DNA methylation and removal of acetyl groups from histones (i.e., deacetylation) combine to __________.

silence certain genes

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

specific binding of activator molecules to enhancers protein-protein interactions that are promoted by the activation domains of activator proteins

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 __________.

steroid hormones

In the human genome, oncogenes __________.

stimulate cell division

In an inducible operon, the inducer is often the __________ in the pathway being regulated; the inducer binds to the __________, which then becomes __________.

substrate ... repressor ... inactive

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

the p53 gene

Both repressible and inducible operons control gene expression at the level of __________.

transcription

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

tumor-suppressor genes

MyoD promotes muscle cell development by __________.

turning on the expression of multiple muscle-related genes

What is the role of proteasomes?

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

In prokaryotic genomes, groups of functionally related genes along with their promoters and operators are found together in

an operon

Cytoplasmic determinants __________.

are coded for by maternal genes

Post-transcriptional controls of gene expression __________.

can include translational controls can include changes to mRNA stability may involve changes to the rate at which an mRNA is translated may involve regulation of mRNA splicing

Most human cancers are __________.

caused by the accumulation of somatic mutations

A scientist clones a regulatory gene that is involved in controlling the expression of other genes, and discovers that the regulatory gene encodes an enzyme that acetylates histones. It is likely that this enzyme regulates gene expression by __________.

causing looser packing of the chromatin at the target gene, thereby enhancing transcription

A bacterium can make the amino acid glycine or absorb it from its surroundings. A biochemist finds that glycine binds to a repressor protein and causes the repressor to bind to the bacterial chromosome, turning off an operon. If it is like other similar operons, the presence of glycine will result in the

cessation of the synthesis of glycine

Which of the following statements is NOT associated with epigenetic inheritance? DNA phosphorylation removal of acetyl groups from histones chemical mutagens DNA methylation histone acetylation

chemical mutagens

In eukaryotes, DNA packing seems to affect gene expression primarily by __________. (

controlling access to DNA

Gene expression in bacteria is regulated primarily by __________.

controlling the transcription of genes into mRNA

A cancer cell __________.

does not respond to the chemical signals that control cell division

In a eukaryote, transcription factors called activators may stimulate gene expression by binding to DNA sites called __________.

enhancers

Enhancers __________.

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

Specific cells that appear undifferentiated under the microscope but are already fated to become muscle cells are called __________.

myoblasts

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

nucleotide sequences in the 3′ untranslated region of the mRNA

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

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