Chapter Nine: the flow of information from DNA to RNA to Protein Flashcards
pairing of ___ is key to transfer information from DNA to RNA to protein
complementary bases
___ of DNA, RNA, and proteins help guide mechanisms of gene expression
polarity (directionality)
the flow of genetic information from DNA via RNA to protein
gene expression
triplet codons of nucleotides represent individual ___
amino acids
a gene’s nucleotide sequence is ___ with the amino acid sequence of the encoded peptide
colinear
each nucleotide is part of only ___
one codon
studies of ___ showed that codons consist of three nucleotides
frameshift mutations
the beginning of a gene establishes a ___ that contains a start and stop codon with multiples of 3 in between
reading frame
change grouping of nucleotides as a result of an insertion or deletion
frameshift mutations
combinations of ___ mutations restore the reading frame
3+ or 3-
template strand of DNA is ___ to mRNA
complementary
RNA-like strand of DNA has the same ___ and ___ as mRNA
polarity and sequence
5’ to 3’ in the mRNA corresponds to the ___ terminus in the polypeptide
N to C
single nucleotide substitutions, conform to the genetic code
missense mutations
genetic code is almost ___
universal
DNA sequences that provide the signal to RNA polymerase for starting transcription
promoters
RNA polymerase adds nucleotides in the ___ direction
5’ - 3’
DNA sequences that provide the signal to RNA polymerase for stopping transcription
terminators
steps of transcription
- RNA polymerase binds to promoter sequence
- sigma factor binds to RNA polymerase to form a holoenzyme
- region of DNA is unwound to form open promoter complex
- phosphodiester bonds form between the first two ribonucleotides
- sigma factor separates from RNA polymerase
- core RNA polymerase loses affinity for promoter, moves in 3’ to 5’ direction on the template strand of DNA
- within transcription bubble, NTPs are added to 3’ end of nascent mRNA
- transcription stops when a termination sequence is reached
eukaryotic genes have ___ that are required for efficient transcription
enhancers
the single strand RNA that results from transcription
primary transcript
in prokaryotes, the primary transcript is ___
the mRNA
in eukaryotes, the primary transcript is ___
processed to make mRNA
3 post-transcriptional modifications in eukaryotes
- 5’ methylated cap added
- 3’ poly-A-tail added
- introns removed by RNA splicing
expressed regions, sequences found in a gene’s DNA and mature mRNA
exons
intervening regions, sequences found in DNA but not in RNA
introns
___ cut out introns
enzymes
exons can be ___ after splicing
shuffled
three short sequences in the primary transcript that determine where splicing occurs
splice donor
branch site
splice acceptor
two ___ remove an intron
sequential cuts
splicing is catalyzed by the ___
spliceosome
two bodies that are made up of RNA and protein
ribosomes
spliceosomes
___ produces different mRNAs from the same primary transcript
alternative splicing
carry specific amino acids and match with mRNA code for assembly of a protein
tRNAs
each tRNA has an ___ that is complementary to an mRNA ___
anticodon
codon
a specific tRNA is ___ to a specific amino acid
covalently coupled
tRNA that is bound to an amino acid
charged tRNA
primary structure of tRNA
nucleotide sequence
secondary structure of tRNA
cloverleaf shape, due to base pairing of short complementary sequences within the tRNA
tertiary structure of tRNA
L shape, formed by 3-dimensional folding
catalyze attachment of tRNAs to specific amino acids
aminoacyl-tRNA synthases
flexibility in base pairing between 3’ nucleotide in codon and 5’ nucleotide in anticodon
wobble
the ___ base has wobble ability
third
tRNAs have ___ bases
unusual
___ are the site of polypeptide synthesis
ribosomes
a ribosome has two subunits composed of ___ and ___
RNA and protein
ribosomes only assemble when ___
they’re needed
subunit that binds to mRNA
small subunit
subunit that has peptide transferase activity, catalyzes formation of peptide bonds
large subunit
in prokaryotes, ribosomes bind to a ___ and an ___
shine-dalgarno box
AUG
three sequential steps of transcription initiation in prokaryotes
- small ribosomal subunit binds to mRNA
- fMet-tRNA positioned in P site
- large subunit binds
steps of translation in prokaryotes
- small ribosomal subunit binds to 5’ cap then migrates to the first AUG codon
- a charged tRNA brings in Met and binds to the mRNA codon in the P site of the ribosome
- the large ribosomal subunit binds and begins activity
- the next charged tRNA brings in the next amino acid corresponding to the nest codon
- peptide bond is formed between Met and the second amino acid
- continues until ribosome reaches a stop codon where the polypeptide is released and the ribosomal subunits break apart
complex of several ribosomes translating from the same mRNA
polyribosome
sometimes ___ or ___ are required to activate the newly translated protein
enzymatic cleavage or addition of chemical constituents
the nucleus separates ___ and ___ in eukaryotes
transcription and translation
eukaryotic promoters are influenced by ___
enhancers
translation ___ differs in prokaryotes and eukaryotes
initiation
mutations that do not alter amino acid sequence
silent mutations
mutations that replace one amino acid with another
missense mutations
missense mutation in which chemical properties of mutant amino acid are similar to the original amino acid
conservative
missense mutation in which chemical properties of mutant amino acids are different from the original amino acid
nonconservative
mutations that change the codon that encodes an amino acid to a stop codon
nonsense mutations
nonsense mutations result in a ___
truncated protein
mutations that result from insertion or deletion of nucleotides within the coding region
frameshift mutations
loss-of-function mutant alleles are usually ___ to wild-type
recessive
mutation that completely blocks function of a gene produce
null (amorphsc) mutations
mutation that produces less of wild-type protein, or less effective mutant protein
hypomorphic mutations
some loss-of-function alleles can show ___
incomplete dominance
some loss-of-function alleles are ___ to wild-type
dominant
one wild-type allele does not produce enough gene product to avoid mutant phenotype
haploinsufficiency
gain-of-function mutations are usually ___
dominant
generate more gene product or the same amount of a more efficient gene produce
hypermorphic mutations
generate gene product with new function or that is expressed at an inappropriate time or place
neomorphic mutations
example of a neomorphic mutation
ectopic expression of leg-determining gene in structures that normally produce antennae in Drosophila
___ alleles prevent the normal protein from functioning
antimorphic (dominant negative)
mutations in genes encoding the components of gene expression have ___
global effects
