Bio Chapter 12

25 July 2022
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Inborn error of metabolism
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a mutation in a gene that is inherited from one or both parents
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What are the three enzymes that are required for Argine synthesis?
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+Omithine, +Citrulline, Arginine
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polypeptide
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linear sequence of amino acid; it denotes structure.
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proteins
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Denotes function.
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Functional protein
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compsed of two or more different polypeptides
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Transcription
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produces an RNA copy of a gene, transcription literally means the act of making a copy.
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Structural genes
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produce RNA molecule that contains the information to specify a polypeptide with a particular amino acid sequence.
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Messenger RNA (mRNA)
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is created from structural genes ,it's function is to carry infomation from the DNA to cellular components called ribosomes
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Ribosomes
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play a key role in the synthesis of polypepties.
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Translation
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the process of synthesizing a specific polypeptide on a ribosome.
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The central dogma of gene expresssion at the molecular level
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In bacteria, transcription and translation occur in the cytoplasm In eukaryotes,transcription and RNA processing occur in the nucleus,whereas translation takes place in the cytosol
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RNA processing
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the RNA transcript, termed pre-mRNA is modified in ways that make it functionally active mRNA.
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where does transcription occur in eukaryotes?
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in the nucleus
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transcription and translation both occur in the same location, where dies this occur and what type of cell is this ?
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cytoplasm, bacteria
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what is the direction of flow of genetic infomation?
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DNA to RNA to protein
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Gene
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an organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product.
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Transfer RNA (tRNA)
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Translates the language of mRNA into that of amino acids.
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Ribosomal RNA(rRNA)
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forms part of ribosomes,which provide the site where translation occurs.
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Promoter
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The site where transcription begins .signals the beginning of transcription
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Terminator
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specifies the end of transcription.signals the end of transcription
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Transcribed region
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part of this region contains the infomation that specifies an amino acid sequence.
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Regulatory sequence
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site for the binding of regulatory proteins.the role of regulatory proteins is to influence the rate of transcription.
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How would removing a terminator from a gene affect transcription?where would transcription end?
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If a terminator was removed, transcription would occur beyond the normal stopping point.eventually,RNA polymerase would encounter a terminator from an adjacent gene,and transcription would end.
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Initiation
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Is a regonition step
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Sigma factor
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a protein that binds to RNA polymerase.Also it recognizes the base sequence of promoter ans binds there.
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RNA polymerase
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the enzyme that synthesizes strands of RNA.
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Elongation
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RNA polymerase synthesizes the RNA transcript for this to occur thesigma factor is released and RNA polymerase slides along the DNA in a way that maintains an open complex as it goes the DNA strand is used as a template for RNA synthesis .
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Template strand
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the portion of the DNA strand that is used as a template for RNA synthesis
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Coding strand
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has the same sequence of bases as the resulting mRNA,except for thymine in the DNA is substituted for uracil in the RNA.It carries information that codes the polypeptide.
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What are similarities and differences between the function of DNA polymerase and that of RNA polymerase?
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Both DNA and RNA polymerase use DNA strands as a templaate and connect the nucleotides to each other in a 5' to 3' direction based on complementarity base pairing.One difference is that DNA polymerase needs a preexisting strand,such as an RNA primer to begin DNA replication.Whereas RNA polymerase can begin the syntheis of RNA on a bare template strand.Another key difference is that DNA polymerase connects deoxyribonucleotides,where as RNA polymerase connects ribonucleotides.
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Transcription factors
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are proteins influenced by the ability of RNA polymerase to transcribe genes
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Introns
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transcribed but not translated into proteins.
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Exons
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sequences contained in the mature mRNA.they are expressed in regions whereas introns are intervening regions that are not expressed because they are removed from the mRNA.
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RNA splicing
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introns are removed and the remaining exons are connected to eachother.
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In what region does translation occur?
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cytosol
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spliceosome
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is comprised of several different subunits knowns as snRNPS(pronounced "snurps").they bind to specific sequences at three locations
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snRNPS
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containsmall nuclear RNA and a set of proteins
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Alternative splicing
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allows a signle gene to encode two or more polypetides with differences in their amino acid sequences/ allows complex eukaryotic species to use the same gene to make different proteins at different stages of development or in different cell types.
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Self-splicing
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RNA itself can catalyze the removal of its own intron.portions of te RNA act like an enzyme to cleave the covalent bonds at the intron-exon boundaries and connect the exons together.
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Ribozyme
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An RNA moecule that catalyzes a chemical reaction.
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Capping
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IS when mature mRNA of eukaryotes have a modified form of guanine covalently attached at the 5' end. this event occurs while a pre-mRNA is being made by RNA polymerase.After mRNA is in the cytosol the cap structure helps to prevent mRNA degration and is recognized by other cap-binding proteins that enable the mRNA to bind to a ribosome for translation.
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Poly A tail
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at the 3' end,most mature eukaryotic mRNAs have a string of adenine nucleotides. the poly A tail is not encoded in the gene sequence.A long poly A tail aids in the export of mRNAS from the nucleus.
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Genetic Code
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specifies the relationship between the sequence of nucleotides in the mRNA and the sequences of amino acids in a polypeptide.
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Codons
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the groups of three nucleotide bases read
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Codons for Pheylalanine (Phe)
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UUU UUC
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Codons for Leu
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UUA UUG CUU CUC CUA CUG
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Start codon
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AUG
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End codons/stop condons/termination codons
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UAA UAG UGA
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Coding sequence
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a region that specified the linear amino acid sequence of a polypeptide.
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If a mutation eliminated the start codon from a gene,how would the mutation affect transcription,and how would it affect translation?
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a structural gene would still be transcribed into RNA if the start codon was missing.however it would not be translated properly.
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Reading frame
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refers to the order in which codons are read during translation.
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If an anticodon in a tRNA molecule had the sequence 3'-ACC-5' which amino acid does it carry?
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It would bind to a 5'-UGG-3' codon and it would carry tryptophan.
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Anticodon
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is a three-based sequence in tRNA molecule that is complementary to a codon in mRNA bind to each other.
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N-terminus
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refers to the presence of a nitrogen atom(N)
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peptide bonds
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connect amino acids together,covalent bonds
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C-terminus
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a carboxyl group is always found at the end of the polypeptide.
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What is the function of the anticodon?
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The function of the anticodon in tRNA is to recognize a codon in an mRNA.
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What is the enzyme that catalyzes that attachment of amino acids to tRNA?
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aminoacyl-tRNA synthetases
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Which describes the hydrolysis of ATP.why is ATP needed to charge a tRNA?
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The attachment of an amino acid to a tRNA is an endergonic reaction.ATP provides the energy to catalyze this reaction.
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Initiation
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a complex is formed between an mRNA molecule,the first tRNA,and ribosomal subunits.
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Initiation factors
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proteins that facilitate the interactions between components.
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What promotes the binding between the mRNA and the small ribosomal subunit?
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A region near the 5' end of the mRNA is complementary to a region of rRNa is the small subunit.These complementary regions hydrogen-bond with each other to promote the binding of the mRNA to the small ribosomal subunit.
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elongation
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the covalent bonding of amio acids to each other,one at a time,to produce a polypeptide.
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release factor
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the three-dimmensional structure of a release factor protein mimics the structure of tRNAs which allows it to fit into the A site.
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Which of the following best represents the centreal dogma of gene expression? a. During transcription,DNA codes for polypeptides. b. During transcription,DNA codes for mRNA,which codes for polypeptides during translation. c.During translation,DNA codes for mRNA,which codes for polypeptides during transcription. d.none of the above.
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b. During transcription,DNA codes for mRNA,which codes for polypeptides during translation.
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Transcription of gene begins at a site on DNA called_____ and ends at a site on DNA known as____. a. The start codon, the stop codon b. A promoter,the stop codon c. the start codon, the terminator d. a promoter, the terminator e.none of the above
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d. a promoter, the terminator
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The functional product of a structural gene is a.tRNA b.mRNA c.rRNA d.a polypeptide e.a,b,and c.
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d.a polypeptide
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During eukaryotic RNA processing,the nontranslated sequences that are removed are called a.exons b.introns c.promoters. d.codons e.ribozymes
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b.introns
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The____ is the site where the translation process takes place. a.mitochondria b.nucleus c.ribosome d.lysosome e.ribozyme
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c.ribosome
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The small subnit of a ribosome is composed of a.protein b.an rRNA molecule c.many proteins d.many rRNA molecules e.Many proteins and one rRNA molecule.
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e.Many proteins and one rRNA molecule.
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The region of the tRNA that is complementary to a codon in mRNA is a. the acceptor stem b.the codon c.the peptidyl site d.the anticodon e.the adaptor loop.
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d.the anticodon
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During initiation of translation,the frist codon,______, enters the ____ and associates with the initiator tRNA. a.UAG,A site b.AUG,A site c.UAG, P site d.AUG, P site e.AUG,E Site
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d.AUG, P site
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The movement of polypeptide from the tRNA in the p Site to the tRNA in the A site is referred to as a.peptide bonding b.aminoacyl binding c.translation d.the peptidyl transfer reaction e.elongation
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d.the peptidyl transfer reaction
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The synthesis of a polypeptide occurs during which stage of translation? a.initiation b.elgongation c.termination d.splicing
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b.elgongation
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What is the function of an aminoacyl-tRNA synthetase?
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Each of these 20 enzymes catalyzes the attachment of a specific amino acid to a specific tRNA molecule.
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How many nucleotides are contained in a single codon? 1 3 4 6 9
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3
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The process that produces mRNA from DNA is called transcription. translation. replication. processing. post-translational modification.
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transcription.
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The processes of transcription and translation are collectively known as RNA processing. gene duplication. protein synthesis. DNA synthesis. gene expression.
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gene expression.
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The transcription process in a eukaryotic gene directly produces _________. rRNA pre-mRNA mRNA DNA Protein
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pre-mRNA
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An organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product is called a _______. chromosome trait allele gene expression
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gene
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Transcription begins near a site in the DNA called the ______. promoter enhancer response element transcription unit regulatory sequence
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promoter
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If a DNA template strand has a sequence of 3′ TACAATGTAGCC 5′, then the RNA produced from it will be which sequence? 3′TACAATGTAGCC5′ 5′ATGTTACATCGG3′ 5′AUGUUACAUCGG3' 3′AUGUUACAUCGG5′ 3′ATGTTACATCGG5′
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5′AUGUUACAUCGG3'
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What protein influences the ability of RNA polymerase to transcribe genes? DNA polymerases DNA helicases transcription factors snRNPs tRNA
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transcription factors
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Intervening sequences that are transcribed, but not translated into protein are called exons. introns. spliceosomes. transposons. transcription factors.
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introns.
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________ enables a single gene to encode two... What process enables a single gene to encode two or more polypeptides that are different in their amino acid sequence. Reverse transcription Self-splicing Capping Alternative splicing Regulatory splicing
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Alternative splicing
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Because more than one codon can specify the same amino acid, the genetic code is said to be repetitive. redundant. reverse. degenerate. wobbly.
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degenerate
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Which of the following statements about the mRNA start codon is INCORRECT? The start codon is only a few nucleotides from the ribosomal binding site. The start codon is usually GGA. The start codon is usually AUG. The start codon specifies the amino acid, methionine. The start codon defines the reading frame.
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The start codon is usually GGA.
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An mRNA sequence is 5′AUG-GGC-ACU-CAU-ACU-UAA3′, where AUG is the start codon and UAA is the stop codon. How many distinct aminoacyl-tRNA synthetases are required to translate the mRNA sequence? 2 3 4 5 6
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4
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What enzyme catalyzes the attachment of amino acids to tRNA molecules? helicase topoisomerase aminoacyl-tRNA synthetase ribosome translation factor
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aminoacyl-tRNA synthetase
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The following mRNA transcript would result in what polypeptide sequence? 5′ ACU-UUC-ACU-AUG-UUU-UUA-UCC-UCC-ACU-CCU-UGA 3′ Use the following codons and the amino acids they encode. AUG = Start or Met; UUU, UUC = Phe; UUA, UUG = Leu; UCU, UCC = Ser; CCU, CCC = Pro; ACU, ACC = Thr; UGA = Stop. Thr-Phe-Thr Phe-Leu-Ser-Ser-Thr-Pro Met-Phe-Leu-Ser-Ser-Thr-Pro Thr-Phe-Thr-Phe-Leu-Ser-Ser-Thr-Pro Met-Phe-Leu-Ser-Ser
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Met-Phe-Leu-Ser-Ser-Thr-Pro
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The genetic code consists of ____ codons that specify amino acids, and ____ codons that do not specify amino acids. 20/3 64/3 60/4 61/3 21/3
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61/3
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There is only one start codon, AUG. This means that all newly-made polypeptides have a methionine at their amino end. all newly-made polypeptides have a methionine at their carboxyl end. the first tRNA will have the anticodon loop 3'-AUG-5'. the 5' end of an mRNA must start with an A. the stop codons each have their own special tRNAs.
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all newly-made polypeptides have a methionine at their amino end.