ch 21 bio 1a
There is about 1,000 times as much DNA in a human cell as in an E. coli cell, but only about 5 times as many genes. What accounts for this discrepancy? (eText Concept 21.4) a) A human cell has much more noncoding DNA. b) Human cells are much larger than E. coli cells. c) E. coli bacteria are less able to respond to their environment than humans. d) The DNA packing is much more complex in a prokaryotic cell. e) Most of the genes in a human cell are turned off.
a) A human cell has much more noncoding DNA.
Who discovered "jumping genes" (transposons)? (eText Concept 21.4) a) McClintock b) Pauling c) Tatum d) Chase e) Crick
a) McClintock
Among the organisms listed below, which has the largest genome? (eText Concept 21.3) a) Polychaos dubia b) the archaean Archaeoglobus fulgidus c) brewer's yeast Saccharomyces cerevisiae d) Homo sapiens e) the Japanese canopy plantParis japonica
a) Polychaos dubia
What factor accounts most for the difference in genome size between vertebrates and prokaryotes? (eText Concept 21.3) a) Vertebrates have more protein-coding genes. b) Vertebrates have more genes for functional RNA molecules. c) Vertebrates have longer and more complex upstream regulatory sequences d) Many genes undergo alternative splicing, so that different proteins with different exon combinations are produced from the same gene. e) All of the listed responses are correct.
a) Vertebrates have more protein-coding genes.
The advantage of copy-number variants (CNVs) over SNPs in human genomic studies is that CNVs __________. (eText Concept 21.6) a) occupy much longer stretches of DNA than SNPs, and are likely to have greater phenotypic consequences b) are far greater in number but of equal size to SNPs c) have revealed significant genetic diversity existing among different human populations at geographic locations both near and far apart d) occur only in noncoding DNA, which generally mutates at a constant rate and is more informative in measuring the genetic variation among human populations e) provide reliable information about human genetic diversity
a) occupy much longer stretches of DNA than SNPs, and are likely to have greater phenotypic consequences
The similarity of the homeobox in many different kinds of organisms is evidence __________. (eText Concept 21.6) a) of the common ancestry of different life-forms b) that it is not responsive to natural selection c) of convergent evolution d) of its recent origin e) of analogy
a) of the common ancestry of different life-forms
Scientists have succeeded in sequencing the Neanderthal genome with DNA extracted from Neanderthal bones. Information from this project might reveal __________. (eText Concept 21.6) a) what genetic differences may be responsible for the superior abilities of modern humans to communicate and make more sophisticated tools b) why Neanderthals became extinct c) whether Neanderthals are the same species as modern humans d) whether Neanderthals had language ability e) All of the listed responses are correct.
a) what genetic differences may be responsible for the superior abilities of modern humans to communicate and make more sophisticated tools
The human genome is thought to contain about how many genes? (eText Concept 21.3) a) 1,000-2,000 b) 20,000-25,000 c) 4,000-6,000 d) 50,000-100,000 e) 13,000-15,000
b) 20,000-25,000
Open Hint for Question 31 in a new window A gene family has been identified that has undergone extensive duplication in humans, but is present in only one or a few copies in other primates or other mammals. What experimental approaches could be used to determine the function of this gene and its significance in human evolution? (eText Concept 21.6) a) Introduce these genes into yeast and study the phenotype of the resulting cells. b) Create knockout mice to determine their phenotype. c) Determine the timing and location of expression of these genes during embryonic development in fruit flies. d) Reduce the number of copies of this gene in a human subject. e) All of the listed responses are correct.
b) Create knockout mice to determine their phenotype.
Chromosomal rearrangements may be important in evolution because __________. (eText Concept 21.5) a) chromosomal rearrangements caused the extinction of dinosaurs, thereby allowing mammals to become dominant b) chromosome rearrangements lead to gene duplication, thus generating a "spare" copy of the gene that is free to evolve and acquire a new function c) chromosome rearrangements may cause genetic diseases d) offspring who inherit two differently arranged sets of chromosomes instantly become a new species e) chromosome rearrangements cause new genes to evolve
b) chromosome rearrangements lead to gene duplication, thus generating a "spare" copy of the gene that is free to evolve and acquire a new function
Recall that the human genome contains roughly 3 billion base pairs per haploid genome, and that about 25% of the mammalian genome is associated with genes, including introns and regulatory sequence. What would be the approximate average length of DNA per human gene, if the genome contained 20,000 genes? (eText Concept 21.4) a) 10,000 base pairs b) 1,000 base pairs c) 40,000 base pairs d) 80,000 base pairs e) 20,000 base pairs
c) 40,000 base pairs
How do transposable elements promote genetic diversity in a population? (eText Concept 21.5) a) A transposable element gene such as reverse transcriptase may become part of a normal cellular gene. b) A transposable element may carry along a gene or an exon to a different locus, leading to exon duplication or exon shuffling. c) A transposable element may cause genetic diversity by any of the above methods. d) Transposable elements that insert into an intron may provide an alternative splice site, leading to a protein with a new exon. e) Transposable element insertion into a regulatory sequence may alter the strength of transcription.
c) A transposable element may cause genetic diversity by any of the above methods.
Once an organism's genome sequence has been determined, how do scientists generally start identifying all the genes within the genome? a) Hybridize the DNA with probes specific for known genes from other organisms. b) Use DNA microarrays to examine the expression of huge numbers of sequences from the genome under different conditions. c) Analyze the sequence using software that scans the sequence for telltale sequence elements such as promoters, transcription start and stop sites, and so on. d) Individually mutate all of the nucleotides within the genome, and determine which mutations cause a detectable phenotype. e) None of the listed responses is correct.
c) Analyze the sequence using software that scans the sequence for telltale sequence elements such as promoters, transcription start and stop sites, and so on.
What can be learned from comparing the genomes of distantly related species, such as yeast and humans, or plants and fruit flies? (eText Concept 21.6) a) Conserved genes indicate that they were transferred laterally from one species to the other. b) Genes found in humans but not in yeast provide insight into human evolution. c) Conserved genes provide insight into their evolutionary relationships. d) All of the listed responses are correct. e) None of the listed responses is correct.
c) Conserved genes provide insight into their evolutionary relationships.
Open Hint for Question 32 in a new window Why might a dog genome sequencing project prove particularly informative, compared to other mammalian genomes? (eText Concept 21.6) a) The dog genome is smaller than other mammalian genomes. b) Dogs are more closely related to humans than other mammals. c) Genetic variation between breeds may be linked to phenotypic variation. d) Dogs have large brains and sophisticated communication abilities. e) The dog genome lacks transposons.
c) Genetic variation between breeds may be linked to phenotypic variation.
Why might the number of genes in eukaryotic genomes underestimate the number of different proteins that an organism makes? (eText Concept 21.3) a) Organisms take up foreign DNA and make proteins encoded by these foreign DNA molecules. b) The genome rearranges its DNA so that different cells can make different proteins. c) Many genes undergo alternative splicing, so that different proteins with different exon combinations are produced from the same gene. d) All of the listed responses are correct. e) None of the listed responses is correct.
c) Many genes undergo alternative splicing, so that different proteins with different exon combinations are produced from the same gene.
The highly conserved sequence element present within homeotic genes is called the __________. (eText Concept 21.6) a) bicoid b) morphogen c) homeobox d) ced-3 e) TATA box
c) homeobox
What is a valid rationale for sequencing the chimpanzee genome? (eText Concept 21.6) a) to determine whether another human pathogen such as HIV could originate from viruses that infect chimpanzees b) to reconstruct chimpanzees if they become extinct c) to determine what genetic changes determine uniquely human features such as large brains and language ability d) to be able to study human diseases in chimpanzees e) to determine whether any chimpanzee genes could be used to genetically engineer superior humans, or vice versa
c) to determine what genetic changes determine uniquely human features such as large brains and language ability
In the U.S., the National Center for Biotechnology Information (NCBI) provides __________. (eText Concept 21.2) a) a database of protein structures b) BLAST c) Genbank d) All of the listed responses are correct. e) None of the listed responses is correct.
d) All of the listed responses are correct.
The eukaryotic genome is much less tidy and compact than the genomes of prokaryotes. Eukaryotes, but not prokaryotes, have __________. (eText Concept 21.4) a) a large proportion of their DNA that is never expressed b) introns, some of which are bigger than the genes they interrupt c) short sequences of nucleotides that may be repeated thousands of times d) All of the listed responses are correct. e) None of the listed responses is correct.
d) All of the listed responses are correct.
Which of the following best describes the experimental evidence that the FOXP2 gene is vital to the normal development of vocalization in vertebrates and yet has evolved among different vertebrate lineages? (eText Concept 21.6) a) Knocking out one of the two FOXP2 genes in mice and humans had no effect on the development of vocalization in either species. b) Replacing the FOXP2 gene in mice with a humanized version of the gene had no negative effects on the mice but did lead to the development of brain cells in neural circuits that are associated with speech development in humans. c) When scientists knocked out the FOXP2 gene in human subjects, they observed the development of severe speech and language impairment. d) Replacing the FOXP2 gene in mice with the human form of the gene had a neutral effect on development of vocalization in mice. e) Replacing the mouse FOXP2 gene with songbird versions of the gene caused the transgenic mice to vocalize like songbirds.
d) Replacing the FOXP2 gene in mice with the human form of the gene had a neutral effect on development of vocalization in mice.
An example of a systems biology experiment might be __________. (eText Concept 21.2) a) determining the normal biochemical function of the gene involved in insulin resistance b) comparing the insulin resistance gene in human, mouse, and chimpanzee genomes c) determining what gene mutation causes insulin resistance d) determining how insulin resistance affects transcription of thousands of other genes in the genome e) All of the listed responses are correct.
d) determining how insulin resistance affects transcription of thousands of other genes in the genome
The molecular data indicate that the globin gene family __________. (eText Concept 21.5) a) evolved from a common ancestor of the alpha- and beta-globin genes, but that myoglobin and leghemoglobin arose from a different ancestor b) evolved through exon duplication c) arose through convergent evolution, where genes of different ancestry become similar over time because they have the same function d) evolved from a common globin gene ancestor that gave rise to both alpha- and beta-globin genes, as well as myoglobin and plant leghemoglobin e) has two distinct evolutionary lineages, originating from an ancestral alpha-globin gene and an ancestral beta-globin gene
d) evolved from a common globin gene ancestor that gave rise to both alpha- and beta-globin genes, as well as myoglobin and plant leghemoglobin
What tool or resource is useful for identifying previously unknown protein-coding genes in a genomic DNA sequence? a) plasmids b) DNA microarrays c) protein structure database d) software that searches for translational start and stop signals e) All of the listed responses are correct.
d) software that searches for translational start and stop signals
Although it contains roughly the same number of genes as the nematode genome, the human genome is thought to produce greater phenotypic diversity by means of __________. (eText Concept 21.3) a) regulation of gene expression by miRNAs b) post-translation addition of carbohydrates to polypeptides c)alternate splicing of RNA transcripts d) post-translational cleavage of a polypeptide into active forms e) All of the listed responses are correct.
e) All of the listed responses are correct.
The number of genes in an organism's genome is not a perfect indication of the organism's complexity because __________. (eText Concept 21.3) a) individual genes can be expressed in more or less complex ways in different organisms b) alternative splicing can increase the number of polypeptides made from a single pre-mRNA c) individual polypeptides can interact to form multiple types of protein complexes d) post-translational modifications can increase the types of proteins produced by a single gene e) All of the listed responses are correct.
e) All of the listed responses are correct.
Why might active transposons be rare in natural populations? (eText Concept 21.5) a) Organisms do not wish to evolve new genes. b) Multiple copies of a transposon suppress each other. c) The immune system attacks active transposons as foreign invaders. d) Transposons have a dramatically higher rate of mutation than other genes. e) Individuals with active transposons are usually eliminated by natural selection, because transposition events usually produce harmful mutations.
e) Individuals with active transposons are usually eliminated by natural selection, because transposition events usually produce harmful mutations.
How can the varying fitness of double-mutant yeast cells provide insights into interactions between gene products?(eText Concept 21.2) a) If double-gene mutants produced smaller colonies than single-gene mutants, then the two genes and their products likely interact. b) If double-gene mutants produced larger colonies than single-gene mutants, then the two genes and their products likely interact. c) If double-gene mutants produced colonies equal in size to single-gene mutants, then the two genes and their products do not interact. d) The first and second listed responses are correct. e) The first, second, and third listed responses are correct.
e) The first, second, and third listed responses are correct.
Alu elements __________. (eText Concept 21.4) a) make up nearly 50% of the human genome b) are found only in the human genome c) are present in all mammals d) encode their own transposase e) are derived from or related to transposable elements
e) are derived from or related to transposable elements
Multigene families arise as a result of __________. (eText Concept 21.5) a) the action of restriction enzymes b) protein degradation c) transformation d) RNA splicing e) errors during DNA replication and recombination
e) errors during DNA replication and recombination
Evolution can rapidly alter a protein-coding gene so it encodes a protein with a different structure and function through __________. (eText Concept 21.5) a) recombinant DNA b) homologous recombination c) single nucleotide substitutions d) mutations in the regulatory sequence of a gene e) exon duplication and exon shuffling
e) exon duplication and exon shuffling
Open Hint for Question 6 in a new window Studies that determine gene annotation __________. (eText Concept 21.2) a) simultaneously sequence the genomes of multiple species in an environmental sample b) use fluorescent RNA probes to determine the presence and location of a gene c) determine the frequencies of specific genes throughout the genome d) attempt to determine a gene's exact locus in the genome e) identify which genes are protein-coding within a genome
e) identify which genes are protein-coding within a genome
Detailed comparison of the human and chimpanzee genomes has revealed that __________. (eText Concept 21.6) a) most differences are in the form of single nucleotide substitutions b) chimpanzees have more chromosomes c) chimpanzee transposons are different from human transposons d) human and chimpanzee genomes are so similar that they should be considered to be the same species e) most differences are in the form of chromosomal rearrangements
e) most differences are in the form of chromosomal rearrangements
Segments of eukaryotic DNA that can move from one site to another in the genome by means of an RNA intermediate are called __________. (eText Concept 21.4) a) alleles b) plasmids c) introns d) transposons e) retrotransposons
e) retrotransposons
How do sequence by synthesis techniques differ from previous sequencing methodologies? a) the application of metagenomic techniques to arranging the sequenced DNA fragments of the genome of interest b) the use dideoxynucleotides to label the ends of DNA fragments c) the use of computer programs to arrange the correct order of DNA fragments that are first sequenced d) the use of sets of unique genetic markers to establish gross genomic structure e) simultaneous sequencing of many small fragments of DNA, thereby reducing the amount a time required to sequence a genome
e) simultaneous sequencing of many small fragments of DNA, thereby reducing the amount a time required to sequence a genome
