Mastering Biology 10

Which of the following is characteristic of the lytic cycle? a) A large number of phages are released at a time. b) Many bacterial cells containing viral DNA are produced. c) Viral DNA is incorporated into the host genome. d) The viral genome replicates without destroying the host. e) The virus-host relationship usually lasts for generations.

a) A large number of phages are released at a time.

How do cells become differentiated? a) Different genes are expressed so that different proteins are produced. b) Paternal effect genes begin the process of differentiation by providing positional information. c) They differentiate through the process of mitosis. d) Some cells contain maternal chromosomes and some contain paternal chromosomes. e) The DNA in each cell changes so that the appropriate proteins are produced.

a) Different genes are expressed so that different proteins are produced.

Which of the following has the largest genome and the fewest genes per million base pairs? a) Homo sapiens (human) b) Haemophilus influenzae (bacterium) c) Drosophila melanogaster (fruit fly) d) Arabidopsis thaliana (plant) e) Saccharomyces cerevisiae (yeast)

a) Homo sapiens (human)

How has gene duplication played a critical role in evolution? a) It produces redundant copies of existing genes, which are then free to mutate and adopt new functions. b) It almost always introduces immediate benefits for the organism. c) It increases the amount of DNA in the genome. d) It increases the number of pseudogenes in the genome. e) It increases the likelihood of viral infection in cells.

a) It produces redundant copies of existing genes, which are then free to mutate and adopt new functions.

Which of the following statements about genome sizes is true? a) Most eukaryotes have larger genomes than most prokaryotes. b) Species within a phylogenetic group such as flowering plants or insects have similar genome sizes. c) Large animals have larger genomes than plants. d) The human genome is the largest and most complex. e) All of the above statements are true.

a) Most eukaryotes have larger genomes than most prokaryotes.

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have a) T4 protein and T4 DNA. b) T4 protein and T2 DNA. c) T2 protein and T4 DNA. d) T2 protein and T2 DNA. e) a mixture of the DNA and proteins of both phages.

a) T4 protein and T4 DNA.

By what mechanism might transposons contribute to gene duplication? a) Transposons may promote unequal crossing over during meiosis. b) Transposon insertion may disrupt an exon. c) Transposons may promote accidents in meiosis, leading to polyploidy. d) Transposons cause failure of chromosomes to segregate during mitosis. e) Transposons may lead to slippage of DNA polymerase during DNA replication.

a) Transposons may promote unequal crossing over during meiosis.

Which viruses have single-stranded RNA that acts as a template for DNA synthesis? a) retroviruses b) lytic phages c) bacteriophages d) viroids e) proviruses

a) retroviruses

What is considered to be the first evidence of differentiation in the cells of an embryo? a) the occurrence of mRNAs for the production of tissue-specific proteins b) cell division occurring after fertilization c) changes resulting from induction d) determination of specific cells for certain functions e) changes in the size and shape of the cell

a) the occurrence of mRNAs for the production of tissue-specific proteins

The number of genes correlates with _____. a) the size of the genome in prokaryotes b) and is approximately equal to the number of different proteins that a species can make c) being much higher among Eubacteria than in Archaea d) the size of the genome in eukaryotes e) being higher in Archaea than in eukaryotes

a) the size of the genome in prokaryotes

Eukaryotic genomes are larger than prokaryotic genomes. a) true b) false

a) true

Transposons may or may not leave a copy behind at the original site, whereas retrotransposons always leave a copy behind at the original site. a) true b) false

a) true

Transposons move by means of a DNA intermediate, whereas retrotransposons move by means of an RNA intermediate. a) true b) false

a) true

Fragments of DNA have been extracted from the remnants of extinct woolly mammoths, amplified, and sequenced. These can now be used to a) understand the evolutionary relationships among members of related taxa. b) study the relationships among woolly mammoths and other wool-producers. c) appreciate the reasons why mammoths went extinct. d) clone live woolly mammoths. e) introduce into relatives, such as elephants, certain mammoth traits.

a) understand the evolutionary relationships among members of related taxa.

Why is it ineffective to treat viral disease with antibiotics? a) Due to excessive antibiotic use, most viruses have evolved to be resistant to antibiotics. b) Antibiotics inhibit enzymes specific to bacteria and have no effect on virally encoded enzymes. c) Pathogenic RNA viruses have a high rate of mutation, producing new genetic varieties that are insensitive to antibiotic treatment.

b) Antibiotics inhibit enzymes specific to bacteria and have no effect on virally encoded enzymes.

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following might best give you an answer? a) You use an antibiotic known to prevent translation. b) You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same. c) An analysis of amino acid production by the cell shows you that there is an increase at this stage of embryonic life. d) You assess the position and sequence of the promoter and enhancer for this gene. e) You explore whether there has been alternative splicing by examining amino acid sequences of very similar proteins.

b) You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

Use the following information to help you answer the following question. Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16. 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) differential gene regulation over time c) differential translation of mRNAs d) intron activation e) pseudogene activation

b) differential gene regulation over time

Eukaryotes have higher gene densities than prokaryotes. a) true b) false

b) false

Retrotransposons reverse the effects of transposons. a) true b) false

b) false

Within eukaryotes, genome size is a reliable predictor of phenotypic complexity. a) true b) false

b) false

Multigene families are a) usually clustered at the telomeres. b) identical or similar genes that have evolved by gene duplication. c) groups of enhancers that control transcription. d) sets of genes that are coordinately controlled. e) equivalent to the operons of prokaryotes.

b) identical or similar genes that have evolved by gene duplication.

Double-stranded viral DNA is incorporated into a host cell as a _____. a) promoter b) provirus c) transposon d) lac e) homeoboxes

b) provirus

The genetic material of HIV consists of _____. a) single-stranded DNA b) single-stranded RNA c) double-stranded DNA d) double-stranded RNA e) none of the above

b) single-stranded RNA

As a result of the lytic cycle, _____. a) the host cell is not destroyed b) the host cell's DNA is destroyed c) viral ribosomes are produced d) viral DNA is incorporated into host cell DNA e) a prophage is created

b) the host cell's DNA is destroyed

Which of the following is a major distinction between a transposon and a retrotransposon? a) A retrotransposon always uses the copy-paste mechanism, while a transposon uses cut and paste mechanism. b) A transposon is related to a virus and a retrotransposon is not. c) A transposon moves via a DNA intermediate and a retrotransposon via an RNA intermediate. d) A transposon always leaves a copy of itself at its original position and a retrotransposon does not. e) The positioning of a transposon copy is transient while that of a retrotransposon is permanent.

c) A transposon moves via a DNA intermediate and a retrotransposon via an RNA intermediate.

All of the statements below are true. Select the statement that best supports the view of most biologists that viruses are nonliving. a) The viral genome may be single-stranded or double-stranded RNA or DNA. b) Viruses are obligate intracellular parasites. c) An isolated virus is unable to replicate its genes or regenerate ATP.

c) An isolated virus is unable to replicate its genes or regenerate ATP.

How do prions, which are misfolded proteins, infect organisms? a) Prions only arise through spontaneous mutation. They are not transmissible. b) Prions recruit ribosomes to make more copies of the wrong form of the protein. c) Prions enter brain cells and cause normal forms of the protein to refold into the prion form. d) Prions enter brain cells through the lymphatic system and make copies of themselves. e) None of the above.

c) Prions enter brain cells and cause normal forms of the protein to refold into the prion form.

Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory? a) Viruses can reproduce only inside host cells. b) Viruses can infect both prokaryotic and eukaryotic cells. c) Viral genomes are usually similar to the genome of the host cell. d) Viruses contain either DNA or RNA. e) Viruses are enclosed in protein capsids rather than plasma membranes.

c) Viral genomes are usually similar to the genome of the host cell.

HIV uses which of the following processes to synthesize a DNA strand using its RNA genome as a template? a) conjugation b) reverse translation c) reverse transcription d) transcription e) translation

c) reverse transcription

Which of the following can be duplicated in a genome? a) DNA sequences above a minimum size only b) DNA sequences below a minimum size only c) sequences, chromosomes, or sets of chromosomes d) entire chromosomes only e) entire sets of chromosomes only

c) sequences, chromosomes, or sets of chromosomes

What type of noncoding DNA comprises the largest portion of multicellular eukaryotic genomes? a) introns b) pseudogenes c) transposons d) gene regulatory sequences e) centromeric sequences

c) transposons

Bioinformatics includes all of the following except a) using computer programs to align DNA sequences. b) using mathematical tools to make sense of biological systems. c) using molecular biology to combine DNA from two different sources in a test tube. d) analyzing protein interactions in a species. e) developing computer-based tools for genome analysis.

c) using molecular biology to combine DNA from two different sources in a test tube.

Bioinformatics includes all of the following except a) development of computer-based tools for genome analysis. b) use of mathematical tools to make sense of biological systems. c) using molecular biology to provide biological information to a system so that it gets expressed. d) analyzing protein interactions in a species. e) using computer programs to align DNA sequences.

c) using molecular biology to provide biological information to a system so that it gets expressed.

Why might the cricket genome have 11 times as many base pairs than that of Drosophila melanogaster? a) The two insect species evolved at very different geologic eras. b) Drosophila are more complex organisms. c) Crickets must make many more proteins. d) Crickets must have more non-coding DNA. e) Crickets have higher gene density.

d) Crickets must have more non-coding DNA.

Emerging viruses arise by a) the spread of existing viruses more widely within their host species. b) mutation of existing viruses. c) the spread of existing viruses to new host species. d) all of the above e) none of the above

d) all of the above

How do prions differ from viruses? a) Unlike viruses, prions are infectious proteins. b) Unlike viruses, prions do not include any nucleic acids. c) Unlike a virus, a prion is a single molecule. d) all of the above

d) all of the above

What is the source of a viral envelope? a) host cell DNA b) prophages c) provirus d) host cell membrane e) viral glycoproteins

d) host cell membrane

What is proteomics? a) the study of how a single gene activates many proteins b) the study of how amino acids are ordered in a protein c) the totality of the functional possibilities of a single protein d) the study of the full protein set encoded by a genome e) the linkage of each gene to a particular protein

d) the study of the full protein set encoded by a genome

What is the goal of comparative genomic studies? a) to identify homologues in model organisms for genes involved in human disease b) to study how genomes evolve c) to identify genes that are important for evolution of a particular species d) to study genetic variation within a species or a population e) All of the above are goals of comparative genomic studies.

e) All of the above are goals of comparative genomic studies.

Why are viruses called obligate intracellular parasites? a) They must use a host cell's amino acids to synthesize proteins. b) They must use a host cell's nucleotides for transcription and replication. c) They must use a host cell's metabolic enzymes and pathways to obtain energy. d) They must use a host cell's ribosomes to synthesize proteins. e) All of the above.

e) All of the above.

Which of the following is a representation of gene density? a) C. elegans has ~20,000 genes. b) Humans have 27,000 bp in introns. c) Humans have 2,900 Mb per genome. d) Fritillaria has a genome 40 times the size of a human. e) Humans have ~25,000 genes in 2,900 Mb.

e) Humans have ~25,000 genes in 2,900 Mb.

What is the function of reverse transcriptase? a) It catalyzes the formation of a polypeptide from an RNA template. b) It catalyzes the formation of DNA from a polypeptide template. c) It catalyzes the formation of RNA from a polypeptide template. d) It catalyzes the formation of RNA from a DNA template. e) It catalyzes the formation of DNA from an RNA template.

e) It catalyzes the formation of DNA from an RNA template.

Use the following information to help you answer the following question. Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16. How might identical and obviously duplicated gene sequences have gotten from one chromosome to another? a) by deletion followed by insertion b) by transcription followed by recombination c) by normal meiotic recombination d) by normal mitotic recombination between sister chromatids e) by chromosomal translocation

e) by chromosomal translocation

A multigene family is composed of a) multiple genes whose products must be coordinately expressed. b) the many tandem repeats such as those found in centromeres and telomeres. c) a gene whose exons can be spliced in a number of different ways. d) a highly conserved gene found in a number of different species. e) genes whose sequences are very similar and that probably arose by duplication.

e) genes whose sequences are very similar and that probably arose by duplication.

The lytic cycle of bacteriophage infection ends with the _____. a) replication of viral DNA b) entry of the phage protein coat into the host cell c) assembly of viral particles into phages d) the injection of phage DNA into a bacterium e) rupture of the bacterium

e) rupture of the bacterium

In the lysogenic cycle _____. a) host DNA is destroyed and viral DNA is replicated b) a bacterium replicates without passing viral DNA to its daughter cells c) viral DNA is destroyed and host DNA is replicated d) a bacterium divides once before the lytic cycle is initiated e) viral DNA is replicated along with host DNA

e) viral DNA is replicated along with host DNA