Chapter 15 Flashcards
hypothesis showing the direct relationship between genes and enzymes
one gene-one enzyme hypothesis
restatement of this one gene-one enzyme hypothesis, taking into account that some proteins consist of more than one polypeptide and not all proteins are enzyme
one gene-one polypeptide hypothesis
the mechanism by which the information encoded in DNA is made into a complementary RNA copy
transcription
the use of the information encoded in mRNA to assemble amino acids into a polypeptide
translation
the name give by Francis Crick to the flow of information from DNA to RNA to protein
central dogma
The DNA strand that is copied into an RNA molecule during gene transcription
template strand
A gene encoding a protein
protein-coding gene
an RNA molecule that serves as a template for protein synthesis
messenger RNA (mRNA)
the nucleotide information that specifies the amino acid sequence of a polypeptide
genetic code
each 3-letter word (triplet) of the genetic code
codon
a codon that specifies an amino acid
sense codons
the first codon read in an mRNA in translation-AUG
start codon/ initiator codon
A codon that does specify amino acids. the 3 nonsense codons are UAG, UAA, and UGA
stop codons/nonsense codon/termination codon
the feature of the genetic code in which with 2 exceptions, more than one codon represents each amino acid
degeneracy
the sequential nature of the words of the nucleic acid code, with no indicators such as commas or spaces to mark the end of one codon and the beginning of the next
commaless
A feature of the nucleic acid code, with the same codons specifying the same amino acids in all living organisms
universal
the site to which RNA polymerase binds(prokaryotes) or to which general transcription factors bind and recruit RNA polymerase (eukaryotes) for initiating transcription of a gene
promoter
a region of DNA that transcribes a single primary transcript
transcription unit
in transcription, the step in which the molecular machinery that carries out transcription assembles at the promoter and begins synthesizing an RNA copy of the gene. in translation, the step in which the translation components assemble on the start codon of the mRNA
initiation
in eukaryotes, the proteins required for RNA polymerase to initiate transcription or that regulate that process. one class of transcription factors recognizes and binds to the promoter in the area of the TATA box and then recruit RNA polymerase
transcription factor (TF)
an enzyme that catalyzes the assembly of ribonucleotides into and RNA strand
RNA polymerase
in transcription, the step in which RNA polymerase (RNA polymerase II in eukaryotes) moves along the gene extending the RNA chain, with the DNA continuing to unwind ahead of the enzyme. in translation, the step in which the assembled translation complex reads the string of codons in the mRNA one at a time while joining the specified amino acids into the polypeptide
elongation
in transcription, the step in which transcription ends and the RNA transcript and RNA polymerase (RNA polymerase II in the case of eukaryotes) are released from the DNA template. in translation, the step in which the translation complex disassembles after the last amino acid of the polypeptide specified by the mRNA has been added to the polypeptide
termination
in eukaryotes, the proteins required for RNA polymerase to initiate transcription or that regulate that process. one class of transcription factors recognizes and binds to the promoter in the area of the TATA box and then recruit RNA polymerase
transcription factors
specific DNA sequence for a gene that signals the end of transcription of a gene. terminators are common for prokaryotic genes
terminators
a gene encoding an RNA that is not translated; that is, a gene other than a protein-coding gene
noncoding RNA genes
the part of an mRNA between the 5’ end of the molecule and the start codon; this region does not code for amino acids
5’ untranslated region (5’ UTR)
the part of an mRNA between the stop codon and the 3’ end of the molecule; this region does not code for amino acid
3’ untranslated region (3’ UTR)
the primary transcript of a eukaryotic protein-coding gene, which is processed to form messenger RNA
precursor-mRNA (pre-mRNA)
in eukaryotes, a guanine-containing nucleotide attached in a reverse orientation to the 5’ end of pre-mRNA and retained in the mRNA produced form it. on an mRNA is the site where ribosomes attach to initiate translation
5’ cap
sequence near the 3’ end of a eukaryotic gene which, in the pre-mRNA transcript of the gene, specifies where the transcript should be cleaved. once cleaved, a poly(A) tail is added to the 3’ end of the RNA
polyadenylation signal
the string of A nucleotides added posttranscriptionally to the 3’ end of a cleaved pre-mRNA molecule and retained in the mRNA produced from it that enables the mRNA to be translated efficiently and protects it from attack by RNA-digesting enzymes in the cytoplasm
poly(A) tail
a non-protein-coding sequence that interrupts the protein-coding sequence in a eukaryotic gene and are removed by splicing in the processing of pre-mRNA to mRNA
introns
an amino acid-coding sequence present in pre-mRNA that is retained in a spliced mRNA that is translated to produce a polypeptide
exons
process that removes introns from pre-mRNAs and joins exons together
mRNA splicing
a complex formed between the pre-mRNA and small ribonucleoprotein particles, in which mRNA splicing takes place
spliceosome
a complex of RNA and proteins
small ribonucleoprotein particles
mechanism by which a pre-mRNA in a eukaryotic cell is processed by reactions that join exons in different combinations to produce different mRNAs from a single gene
alternative splicing
molecular evolutionary process that combines exons of 2 or more existing genes to produce a gene that encodes a protein with an unprecedented function
exon shuffling
the RNA that brings amino acids to the ribosome for addition to the polypeptide chain
transfer RNA (tRNA)
the 3-nucleotide segment in a tRNA that pairs with a codon in an mRNA
anticodon
hypothesis stating that the complete set of 61 sense codons can be read by fewer than 61 distinct tRNAs because of particular pairing properties of the bases in the anticodons
wobble hypothesis
the process of adding an amino acid to a tRNA
aminoacylation/charging
a mutant strain that requires for its growth a nutrient supplement that i not needed by the wild-type strain
auxotrophs
a tRNA linked to its “correct” amino acid, which is the finished product of aminoacylation
aminoacyl-tRNA
an enzyme that catalyzes aminoacylation
aminoacyl-tRNA synthetase
a ribonucleoprotein particle that carries out protein synthesis by translating mRNA into chains of amino acids
ribosomes
the RNA component of ribosomes
ribosomal RNA (rRNA)
the site where the incoming aminoacyl-tRNA carrying the next amino acid to be added to the polypeptide chain binds to the mRNA
A(aminoacyl) site
the site in the ribosome where the tRNA carrying the growing polypeptide chain is bound during translation
P(peptidyl) site
the site where an existing tRNA binds before its release from the ribosome in translation
E(exit) site
a protein that aids an initiation step of translation
initiation factors (IF)
in translation initiation in prokaryotes, a sequence just upstream of the start codon that directs the small ribosomal subunit to bind and orient correctly for the complete ribosome to assemble and start translating in the correct spot
ribosome binding site
the series of codons for a polypeptide encoded by the mRNA
reading frame
a protein that aids in an elongation step of translation
elongation factor (EF)
an enzyme that catalyzes the reaction in which an amino acid is cleaved from the tRNA in the P site of the ribosome and forms a peptide bond with the amino acid on the tRNA in the A site of the ribosome
peptidyl transferase
A tRNA linked to a growing polypeptide chain containing 2 or more amino acids
peptidyl-tRNA
an RNA-based catalyst that is part of the biochemical machinery of all cells
ribozyme
a protein that recognizes stop codons in the A site of a ribosome translating an mRNA and terminates translation
release factor/termination factor
the entire structure of an mRNA molecule and the multiple associated ribosomes that are translating it simultaneously
polysome
“guide” protein that binds temporarily with newly synthesized proteins, directing their conformation toward the correct tertiary structure and inhibiting incorrect arrangements as the new proteins fold
chaperones/chaperonins
a short segment of amino acids to which the signal recognition particle binds, temporarily blocking further translation. is found on polypeptides that are sorted to the endoplasmic reticulum
signal peptide/signal sequence
a mechanism by which a polypeptide being sorted via the endomembrane system in a eukaryotic cell begins its import into the endoplasmic reticulum simultaneously with translation of the mRNA encoding the polypeptide
cotranslational import
a mechanism by which proteins are sorted to their final cellular locations in a eukaryotic cell after they have been made on free ribosomes in the cytosol
posttranslational import
short amino acid sequence on a protein that serves to direct the protein to the appropriate organelle (other than the nucleus or ER) in a eukaryotic cell
transit sequences
a short amino acid sequence in a protein that directs the protein to the nucleus
nuclear localization signals
a spontaneous and heritable change in DNA
mutations
a base-pair substitution mutation in a protein-coding gene that results in a different amino acid in the encoded polypeptide than the normal one
missense mutation
a base-pair substitution mutation in a gene in which the base-pair change results in a change from a sense codon to a nonsense codon in the mRNA. the polypeptide translated from the mRNA is shorter than the normal polypeptide because of the mutation
nonsense mutation
a base-pair substitution mutations in a protein-coding gene that does not alter the amino acid specified by the gene
silent mutation
mutation in a proteincoding gene that causes the reading frame of an mRNA transcribed from the gene to be altered, resulting in the production of a different, and nonfunctional, amino acid sequence in the polypeptide
frameshift mutation
a sequence of DNA that can move from one place to another within the genome of a cell
transposable element (TEs)
the movement of a transposable element from one site to another in a genome
transposition
the location in a genome to which a transposable element moves when it transposes
target site
transposable element that contains only genes for its transposition
insertion sequences
an enzyme that catalyzes some of the reactions inserting or removing the transposable element from the DNA
transposase
a bacterial transposable element with an inverted repeat sequence at each end enclosing a central region with one or more genes
transposon
a transposable element that transposes via an intermediate RNA copy of the transposable element
retrotransposons
