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70 terms

chapter 17

STUDY
PLAY
which of the following variations on translation would be most disadvantageious for a cell
translating polypetides directly from DNA
garrod hypothesized that inborn errors of metabolism such as alkaptonuria occur because
metabolic enzymes require vitamin cofactors, and affected indiviudals have significant nutriitonal deficiences
garrods info about enzyme alteration resulting in alkaptonuria led to further elucidation of same pathway in humans, phenylketonuria occurs when aontehr enzyme in the pathway is altered or missing, resuliting in a failure of phe to be metabolized to another amino tyrosine, tyrosine is an earlier substrate in the pathway altered in alkaptonuria. how might PKU affecte presnece or absence of alkaptonuria
it would have no effect, becase tyrosine is also available from the diet
the nitrogenous base adenine is found in all members of which group
ATP RNA and DNA
a particular triplet of bases in the template strand of DNA is 5 AGT 3, the corresponding codon for mRNA transcribed is
3 UCA 5
the genetic code is essentially the same for all organisms, from this one can logically assume which of the following
a gene from an organism can tehoretically be expressed by any other organism
the universal genetic code is now known to have exceptions, evidence for this can be found if which of the following is true
if UGA usually a stop codon, is found to code for an amino acid such as tryptophan
which of hte following nucleotide triplets best represents a codon
a triplet in teh same reading fram as an upstream AUG
which of hte following provides some evidence that RNA probably evolved before DNA
DNA poly uses primer, usually made of RNA
which of the following statements best describes teh termination of transcription in pros
RNA poly transcribes through the termination sequence, causing polymerase to sperate from DNA and release transcript
which of the following does not occur in prokaryoticgene expresion but in eukariotic gene expression
a poly-A tail is added to the 3; end of the mRNA and a cap to the 5 end
RNA polymerase in a pro is compoused of several subunits, most are the saem for transcription of any gene, but one known as sigma varies considerably. which is themost probably advantage for the organism of such sigma switching
it might allow the poly to recognize different promoters under certain enviromental conditions
which of hte following is the funcition of a poly-A signal seuqence
it codes for a sequence in eukaryotic transcripts that signals enzymatic cleavege 10-35 nucleotides away
in euks there are several differnt types of RNA poly, which type is involved in transcription of mRNA for a globin protein
RNA poly II
transcription in euks requires which of the following in addtion to RNA poly
several transcription factors
part of the promotor, called the TATA box, is said to be highly conserveed in evolution. which of the following might this illustratte
any mutation in the sequence is selected against
the TATA sequence is found only several nucleotides away from the start site of transcription, this probably relates to which of the following
the number of hydrogen bonds between A and T in DNA
what is a ribozyme
an RNA with enzymatic activity
a transcription unit that is 8000 nucleotides long may use 1200 nucleotides to make a product consisting of 400 amino acids, this is explained by
many noncoding stretches of nucleotides are present in mRNA
during splicing, which molecular component of the spliceosome catalyzes the excision reaction
RNA
alternative RNA splicing
can allow production of proteins of different sizes from a single mRNA
in structural organization of many eukaroytic genes, individual exons may be related to which of the folowing
the various domains of the poly peptide product
in an experimental situation, a student researcher inserts an mRNA molecule into a euk cell after he has removed its 5 cap and poly A tail, what would you expect him to find
the molecule is digested by exonucleases since it is no longer protected by the 5 end
use model 5 UTR E1 I1 E2 I2 E3 I3 E4 UTR 3, which components of the molecule will also be found in mRNA in the cytosol
5 UTR E1 E2 E3 E4 UTR 3
use model 5 UTR E1 I1 E2 I2 E3 I3 E4 UTR 3, when spliceosome binds to elements of this sturcture, where can it attagce
to the end of an intron
use model 5 UTR E1 I1 E2 I2 E3 I3 E4 UTR 3 which of hte following is a useful feature of introns for this model
introns allow exon shuffling
use model 5 UTR E1 I1 E2 I2 E3 I3 E4 UTR 3 suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5 end of the intron I1, what might occur
inclusion of I1 in the mRNA
use model 5 UTR E1 I1 E2 I2 E3 I3 E4 UTR 3 suppose an induced mutation removes most of the 5 end of the 5 UTR, what might result
removal of the 5 UTR also removes the 5 cap and mRNA will quicly degrade
a particular triplet of bases in the coding sequence of DNA is AAA, the anticodeon on the tRNA that binds the mRNA codon is
UUU
accuracy in the translation of mRNA into the primary structure of a polypetide depends on specificity in the
bonding of the anticodon to the codon and th attachment of aminos to the tRNAs
what is the function of GTP in translation
GTP energizes the formation of hte initaiton complex, usuing intiation factors
a mutant bac cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phe, this consequence of the cell will be that
proteins in the cell will inculde lysine instead of phe at the amion acid positions specifided by teh codon UUU
there are 62 mRNA codons that specify an amino, but only 45 tRNAs, this is explained by
the rules of base pairing betwen the third base of a codon and tRNA are flexible
which of the following is the first even to take place in translation in euks
small subunit of ribosome reconginzes and attaches to 5 cap of mRNA
what is a function of a signal peptide
to translocate polypetides across the ER membrane
when translating secretory or membrane proteins, ribosomes are directed to the ER membrane by
a signal reception particle that brings ribosomes to a receptor protein the ER membrane
an experimenter has altered teh 3 end of the tRNA correspondeing to the amion meth in such a way as to remove the 3 AC what will result
the amino acid meth will not bind
the process of translation, whether in pros or euks, requires tRNAs amino acids, ribosomal subunits and
polypeptide factors plus GTP
when the ribo reaches a stop codon on the mRNA, no correspoindning tRNA enters the A sight, if the translation reaction were to expermientally be stopped at this point, hwich of hte following would you be able to isolate
an assembled ribosome with a polypeptide attached to the tRNA in the P site
what is the function of release factor?
it binds to teh stop codon in the A sight in the place of tRNA
when the function of the newly made polypeptide is to be secreted from the cell where it has been made, what must occur
its signal sequence must target it to teh ER from which it goes to the Golgi
suppose that a mutation alters the formation of a tRNA so that it will attach to the same amino acid but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA, which makes leu,
one mutated tRNA molecule will be relatively inconsequential because it will be completed with many normal ones
why might a point mutation in DNA make a difference in the level of a proteins activity
it might substitute the manio acid in teh active site
Muller discovered Xrays cause mutation in Drosophila, Auerbach later discovered that chemicals have a similar effect, a new chemical food additive is developed for a cereal, why do we test its ability to cause mutation
we want to prevent any increase in mutation frequency
which of the following types of mutation resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product
a deletion of muation
what is the effect of nonsense mutation in the gene
in introduces a premature stop codon in the mRNA
a frameshift mutation could result from
either an insertion or a deletion of a base
which of the followign DNA mutations is the most likely to be damaging to the protein it specifies
a base-pair deletion
which small scale mutation would be most likely to have a catastrpohic effect on functioning of a protein
a base deletion near the start of a gene
teh most commonly occuring mutation in people with cystic fibrosis is a deletion of a singe codon, this results in
a polypeptide missing an amino acid
which of the following mutations casues a phenotypic change
a single nucleotide deletion in an exon coding for an active stie
if aprotein is coded for a single gene and this protein hase 6 clearly defined domains, which number of exons below is the gene likely to have
8
what staement is true about protein synthesis in prokaryotes
translation can begin while transcription is still in progress
waht is the most current description of a gene
a DNA seuqence that is expressed to form a functional product, either RNA or a polypeptide
gene expression in the domain ARchaea in part resembles that of bac and in part that of euk, what way is it most like euk
domain archaea have numerous transcription factors
what is true of transcription in domain archaea
it is roughly simutaneous wiht translation
in comparing DNA replication with RNA transcription in the same cell, which is following is true only of replication
the entire template molecule is represented in teh product
in order for a euk gene tob e engineered into a bac colonly to be expressed, what must be included in addition to the coding exons of the gene
a bacterial promoter sequence
when the genome of a particular species is said to include 20000 protein coding regins, what does this imply
there are alos genes for RNAs other than mRNA
what type of bonding is responsible for maintaining the shape of the tRNA molecule
hydrogen bonding between base pairs
use this: the enzyme polynucleotide phosphorylase randomly assembles nucleotides into a pollynucleotide polymer, you add polynuc phosphorylase to a solution of adenosine triphospate and GTP, how many artifical mRNA 3 nucleotide codons would be possible
8
use this: the enzyme polynucleotide phosphorylase randomly assembles nucleotides into a pollynucleotide polymer, add it to a solution of ATP, GTP and UTP, how many artifical mRNA 3 nuc codons would be possible
27
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. , where does teh tRNA 2 move after this bonding of lysine to teh polypetide
teh E site
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. , which component of the complex described enters teh exit tunnel thru the large subunit of the ribosome
newly formed polypetide
in euk cells, transcription can not begin until
several transcription factors have bound to the promoter
which is not true of acodon
it extends from one end of the tRNA molecule
the antiocodon of a particular tRNA moleucle is
complementary to the corresopnding mRNA codon
which is not true of RNA processing
exons are cut out before mRNA leaves the nucleus
what component is not directly involved in translation
DNA
which mutation would have a harmful effect on the organism
a single nucleotide insertion downstream of and close to teh start of the codon seuqence