Chapter Eight, Test Three Flashcards
where does transcription occur
in nucleus
where does mRNA processing occur
in nucleus
where does translation occur
in cytoplasm
where does posttranslational modifications occur
cytoplasm
what is interesting about the nuclear envelope
has pores allowing mRNA to move into cytoplasm
what is the simplest possible code
a 3 letter code
showing 64 combinations with redundancy
what was an early hypothesis with the genetic code
overlapping code
what is a frame shift mutation
a single nucleotide deletion or insertion causing the read of codes to shift
what allows frame shifts to work
3 deletions, allows area behind mutation to stay the same
what is mRNA
messenger
what RNA is the most diverse in composition
mRNA
what RNA makes up 85 to 90% of cellular RNA
rRNA
from the nucleolar organizer in nucleus
what RNA makes up about 5% of the cellular RNA
tRNA
what RNA is 70 to 80 nucleotides long
tRNA
what RNA has at least 20 types
tRNA
what is the ribosome composition in prokaryotic cells
30 s + 50 s = 70 s
what is the ribosome composition of eukaryotic cells
40 s + 60 s = 80s
transcription of a gene is what
asymmetric
only one strand is copied
the nontemplate strand is also called what and the prime numbers
5’ to 3’
coding strand
the template strand prime numbers
3’ to 5’
mRNA prime numbers
5’ to 3’
how were amino acids discovered
use repeat nucleotides to determine what aa you got
what are the stop codons
UAA, UAG, UGA
what is a nonsense mutation
point mutation turned amino acid codon into stop codon
what are the three steps in transcription
initiation, elongation and termination
how does transcription start
RNA pol binds to promoter on DNA creating holoenzyme complex
what is the open promoter complex
rna Pol holoenzyme and unwound nucleotides
what is needed for RNA pol to get started
2 nucleotides added to 5’
when is end of initiation
when RNA pol releases sigma subunit
what makes a RNA pol
2 alpha, 1 beta, 1 beta prime, and sigma
what is needed for RNA holoenzyme
sigma factor
what happens when sigma factor is release from holoenzyme
RNA pol can move down DNA creating open complex
where are nucleotides added by RNA pol
3’
what are intrinsic terminators
cause RNA pol to terminate transcription on its own
what are extrinsic terminators
RNA pol require additional proteins such as Rho
without Rho how does transcription stop
hairpin loops, signal release of mRNA
what are Tata boxes
prinbow boxes
what are basal transcription factors
bind to parts of DNA such as promoters to activate transcription
transcription factors that bind to promoters in eukaryotes
what are enhancers
bind to activation proteins
what are repressor proteins
can deactivate transcription by binding to promoter
What are the ways rna is processed
methylated cap
poly-a tail
splicing
what happens in methylated capping
methyl transferase adds methyl group to guanine and proceeding nucleotide
what happens in poly-a-tail
ribonuclease cleaves primary transcript to form new 3’ end and poly-a-polymerase addes A’s to 3’ end to help stabilize mRNA
how does splicing work
cut splice donor 3’ end is the acceptor
splice donor attaches to “A” at the branch site forming lariat
2nd cut at acceptor which removes intron
what helps with splicing
splicesome
what is a spliceosome made of
small nuclear proteins (SNRPs) and SnRNA which brings exons together
how are the anticodons arranged on tRNA
3’ to 5’
where is amino acid attached to on tRNA
3’
what attaches aa to tRNA with a covalent bond
aminoacyl-tRNA synthetases
what is a charged tRNA
amino acid attached to tRNA
what is wobble
some tRNAs can recognize more than one codon
3’ end of codon not important
5’ end of anticodon not important
what binds to mRNA for transcription
30s inititally
what does 50s ribosome do
peptidyl transferase which catalyzes formation of peptide bonds joining aa
in prokaryotes what is the start codon for mRNA
formylmethionine
how does ribosome move along mRNA
5’ to 3’
what is the binding site for codon in prokaryote
shine-dalgarno box
what is the start codon for translation
AUG
what does the initiator tRNA carry
fmet
