CHAPTER 8: Gene Expression: The Flow of Information via Central Dogma
order the steps of the splicing of primary transcripts via a spliceosome two exons are joined together 5` splice site is cut 3` splice site is cut a lariat is formed
1. 5` splice site is cut 2. a lariat is formed 3. 3` splice site is cut 4. two exons are joined together
what is the start codon for eukaryotes and what amino acid does it code for
AUG - methionine
when a polypeptide is synthesized, the first amino acid to be put in place is located at the...
N terminus
what is the initiator amino acid used by prokaryotes
N-formylmethionine
what pieces of evidence suggested that RNA could function as intermediary between DNA and protein? RNA can base pair with DNA for each gene, the mRNA has the same number of nucleotides as the DNA the genetic code of DNA is colinear with protein radioactive uracil was incorporated into molecules in the nucleus and then exported to the cytoplasm
RNA can base pair with DNA radioactive uracil was incorporated into molecules in the nucleus and then exported to the cytoplasm
properties of prokaryotic translation that are not found in eukaryotic translation
Shine-Dalgarno sequence to facilitate mRNA binding to the small ribosomal subunit tRNAi^fMET as the initiator tRNA coupling of transcription and translation
what codons do not encode for an amino acid? UGA AUG UAA UAG
UAA, UAG & UGA
nucleotides that are used during transcription
UTP, GTP, CTP & ATP
what is a spliceosome
a multicomponent structure that removes introns found in an RNA
mutations that could act as gain-of-function alleles
a mutation the confers a new activity on a protein a mutation that increases the activity of a protein a mutation that causes a protein to be expressed in a different location
what type of mutation cause a base substitution that changes a UGG codon for tryptophan to UAG
a nonsense mutation (UAG is a stop codon)
a mutation that causes ectopic expression could produce...
a normal protein in wrong tissue or/and at the wrong time
missense mutation
a nucleotide-pair substitution that results in a codon that codes for a different amino acid
a hypermorphic mutation cane generate
a protein with increase activity and an increased amount of a protein
posttranslation modifications
addition of a phosphate group and carbohydrate peptide cleavage
which of the following can cause a frameshift mutation? deletion of three bases deletion of two bases substitution of a single base addition of a single base
addition of a single base deletion of two bases
during transcription, a T in the template strand direction the addition of a(n) __________ in the mRNA, and an A in the template DNA strand directs the addition of a(n) ________ in the mRNA
adenine; uracil
the universality of the genetic code means that.... all organisms have a common ancestor prokaryotes and eukaryotes produce the same proteins all organisms have the same DNA sequence mouse mRNA can be translated by ribosomes from frog egg cytoplasm
all organisms have a common ancestor mouse mRNA can be translated by ribosomes from frog egg cytoplasm
silent mutation
alters a base but does not change the amino acid
a mutation that completely abolishes the function of a gene generates a(n)...
amorphic allele (or mutation)
branch site is located
an A that bonds to the 5` end of the intron
hypomorphic mutation (or allele)
an allele that produces either less of a wild-type protein or a mutant protein with a weak but detectable function.
when cells were exposed to radioactive amino acids, it was observed that protein synthesis occurred in the cytoplasm, what did researchers conclude from this discovery?
an intermediate molecule transports sequence information from the nucleus to the cytoplasm
the order in which amino acids are added to a polypeptide chain is determined by hydrogen bonding between each codon and the ________ of the tRNA carrying the amino acid
anticodon
to bring a specific amino acid into its location on a polypeptide chain, which sequence on transfer RNA must bind to messenger RNA?
anticodon
the 5` & 3` untranslated regions of a mature eukaryotic mRNA....
are located within exons and facilitate efficient translation
splice acceptor is located
at the 3` end of the intron
splice donor is located
at the 5` end of intron
two functions of transfer RNA are to...
bind to a specific codon and carry the amino acid specified by that codon to the growing polypeptide chain
the flow of genetic information in a cell, from DNA to RNA to protein, is described as the __________ _________ of genetics
central dogma
for protein-encoding genes, the RNA-like strand is also called the __________ strand
coding (nonsense)
RNA-like strand is also called
coding strand or sense strand
the CUA codon specifies leucine in yeast cytoplasmic translation, but the same codon specifies theronine in yeast mitochondria, what is the explanation of this phenomenon
codons used in mitochondria show a few exceptions to the universal genetic code
in prokaryotic cells, translation of an mRNA begins before its transcription has been completed. this phenomenon is called
coupling of transcription and translation
both eukaryotic and prokaryotic cells have ribosomes in the
cytoplasm
translation occurs in the
cytoplasm and ribosome
translation
decoding of a mRNA message into a polypeptide chain
the kinky allele of axin causes heterozygous mice to have kinky tails. the protein Axin is part of a large protein complex in mice, but the Axin^kinky protein prevents the whole complex from functioning. the kinky allele acts as a....
dominant negative allele
in what stage of translation are amino acids linked together in the order designated by the codons
elongation
the stage of translation in which amino acid are added one at a time to a growing polypeptide chain is called
elongation
a eukaryotic promoter differs from a prokaryotic promoter because
eukaryotic promoter are bound by histone proteins that must be released
differences between prokaryotic and eukaryotic promoters
eukaryotic promoters are bound by histone proteins that must be released prokaryotic promoter sequences are closer to the transcription start site
T/F: prokaryotic and eukaryotic cells use different genetic codes
false
what type of mutation is caused by the addition or deletion of a number of bases that is not a multiple of 3
frameshift mutation
ectopic expression
gene expression that occurs outside the cell type, tissue, or time where or when the gene is normally expressed.
noncoding genes
genes that are transcribed but not translated
arranging the four RNA nucleotide A, G, C & U in groups of three will all possible combinations leads to a set of codons called the
genetic code
the RNA-like strand of DNA is also called the coding strand because it...
has the same polarity and sequence as the mRNA but with Ts instead of Us
in what type of cell doe the terms transcript and mRNA refer to the same molecule
in a bacterium
intragenic suppression occurs only if...
in the region between two frameshift mutations of opposite sign, a gene still dictates the appearance of amino acids - even if these amino acid are not the same as those appearing the the normal protein
to decipher the genetic code, scientists were able to synthesize radioactively-labeled polypeptides from synthetic messenger RNAs in a(n)...
in vitro translational system
in what stage of translation does a complex form between the ribosomal subunits, one mRNA molecule and the first tRNA molecule
initiation
which of the following occurs relatively often because the genetic code is degenerate? intragenic suppression aucotrophic mutations frameshift mutations
intragenic suppression
sequences of DNA that are not represented in the mature mRNA are called
introns
an mRNA is monocistronic if
it codes for a single polypeptide
mutation in genes encoding molecules that are involved in gene expression, such as, for example rRNA genes, are often ____________ in homozygotes and can cause altered dominant phenotypes in heterozygotes
lethal
monocistronic
mRNA containing the coding region of only one gene.
what type of mutation causes a base substitution in DNA that ultimately leads to a change in the encoded amino acid
missense mutation
eukaryotic mRNAs are ___________ because they contain a single translation initiation site to produce a single type of polypeptide
monocistronic
in some cases of intragenic suppression, the frameshifted part of a protein can be as long as 50 amino acids. this indicates that....
most of the 64 codons code for an amino acid
dominant-negative mutations (or alleles)
mutant alleles that block the activity of wild-type alleles of the same gene, causing a loss of function even in heterozygotes. (Synonymous with antimorphic mutations.)
frameshift mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide
the allele of the Huntington disease gene that is associated with development of Huntington disease produces an oddly functioning protein that has extra glutamine amino acids, causing neural degeneration. this allele is an example of a(n)....
neomorphic mutation
a gain-of-function mutation that confers a new activity on a protein is a(n) ________ mutation and the mutant allele will usually exhibit ________ inheritance
neomorphic; dominant
template DNA strand is also called
noncoding strand or antisense strand
the end of protein synthesis is specified by a __________ _________, which is a triplet of nucleotides in the mRNA molecule
nonsense codon
what type of mutations involve a change from a normal codon to a stop codon?
nonsense mutations
the signal for termination of translation is called a(n) _________ codon
nonsense or stop
a hypomorphic in a gene can produce...
normal levels of a less functional protein decreases levels of the wild-type protein
a snRNP consists of small _______ ______ & proteins
nuclear RNA
what are snRNPs
part of a spliceosome; they recognize the splice sites
a single mRNA that contains the coding information for several distinct polypeptides is...
polycistronic
many bacterial mRNAs are ________ and contain multiple ribosome binding sites
polycistronic
addition of a phosphate group to a polypeptide is a ___________ modification
posttranslation
features of transcription in eukaryotes only
presence of multiple types of RNA polymerases alternative splicing of transcripts can produce multiple types of polypeptides addition of 5` cap to mRNA
each ribosomal subunit is assembled from ribosomal RNA and many different....
proteins
gain-of-function alleles
rare mutations that enhance a gene's function or confer a new activity on the gene's product; does not disable enzyme function
neomorphic mutations (or alleles)
rare mutations that produce a novel phenotype due to production of a protein with a new function or due to ectopic expression of the protein.
functions of transfer RNA (tRNA)
recognize a three base codon in mRNA & carry a specific amino acid
a loss-of-function mutation can...
reduce the amount of functional protein and occur within or outside the coding region
in response to either of the codon CUC or CUU, leucine would be placed at a particular location on a polypeptide chain. the existence of more than one codon for the same amino acid shows that the genetic code is...
redundant (or is a degenerate)
an RNA molecule that has catalytic activity is called a(n)
ribozyme
Crick and Brenner performed experiments using combinations of bacteriophage mutations. if a single nucleotide deletion (-) occurred, which additional mutations or combinations of mutation could suppress the mutant phenotype? two single nucleotide insertions (+ +) three single nucleotide insertions (+ + +) single nucleotide (-) single nucleotide insertion (+) three single nucleotide deletions (- - -) two single nucleotide deletions (- -)
single nucleotide insertion (+) two single nucleotide deletions (- -)
A site
site of aminoacyl-tRNA binding (charged tRNA)
P site
site that contain a tRNA with an attached peptide
E site
site where an uncharged tRNA leaves the ribosome
noncoding genes include those for...
snRNAs, rRNAs & tRNAs
nonsense mutation
subsitution of wrong nucleotide into DNA that produces an early stop codon
transcription
synthesis of an RNA molecule from a DNA template
Nirenberg and Leder were able to determine the particular amino acids specified by most codons in an experiment where a three-nucleotide mRNA molecule caused a ribosome to bind the __________ carrying the corresponding amino acid
tRNA
a codon specifies that correct amino acid by using ________ as an adapter molecule
tRNA
the strand of DNA that is used to produce the RNA transcript is called the ______ strand, while the opposite strand of DNA is called the ________ strand on non-template
template; coding
in what stage of translation do newly produced polypeptides get released from the ribosome
termination
the sequence in DNA that signals the end of transcription is known as the...
terminator
what aspects of the genetic code was revealed by using an in vitro translational system with a three-nucleotide mRNA molecule to cause a ribosome to bind to a labeled tRNA?
the codon that specified a particular amino acid
features of transcription in prokaryotes only
the promoter consists of a -35 and a -10 sequence a single mRNA contains multiple polypeptide start sites a single type of RNA polymerase
the start codon of a gene sequence determines
the reading frame
a mutation in the E. coli tryptophan synthase gene produces glutamic acid (Glu) instead of glycine (Gly) at position 211 of the protein and the bacteria are unable to survive in the absence of tryptophan. a different mutation produces valine (Val) at the same position and the bacteria can survive in the absence of tryptophan. what is the conclusion from this result?
the tryptophan synthase enzyme can function with either Gly or Val at position 211
a scientists performs a cell-free translation with synthetic mRNAs produced from a mixture of 25% A and 75% C. which of the following amino acids would be incorporated into the resulting polypeptides?
theronine, glutamine, proline, histidine, lysine & asparagine
in prokaryotic cells, the coupling of transcription and translation refers to...
translation of an mRNA beginning before its transcription has been completed
