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51 Cards in this Set

  • Front
  • Back
this type of chromatin is condensed and transcriptionally inactive
this type of chromatin is less condensed and transcriptionally active
which type of chromatin ties nucleosomes together in a string (30-nm fiber)?
what histones make up the nucleosome core?
H2A, H2B, H3, H4
what are the purines, and how many rings do they have?
A, G; 2 rings
what are the pyrimidines and how many rings do they have?
C, T, U; 1 ring (pyramids were CUT)
which nucleotide has a ketone?
which nuclotide has a methyl?
thymine (THYmine has a meTHYl)
deamination of cytosine makes what?
which bond is stronger: G-C or A-T? why?
G-C is stronger because it has 3 H bonds
what happens to the melting temperature when you increase the G-C content?
increases (b/c more H bonds)
what is it called when a purine is substituted for a purine or a pyrimidine is substituted for a pyrimidine?
transItion (Identical type)
what is it called when a purine is substituted for a pyrimidine or vice versa?
transVersion (conVersion between types)
what are some exceptions to the universality of the genetic code?
mitochonria, archaeobacteria, mycoplasma, some yeasts
what is a silent mutation
same amino acid - often base change in 3rd position of codon (tRNA wobble)
what is a missense mutation?
changed amino acid (conservative - new aa is similar in chemical structure)
what is a nonsense mutation?
change resulting in an early stop codon - stop the nonsense!
what are the stop codons?
what is the mRNA initiation codon and what does it code for in eukaryotes?
AUG, methionine (AUG inAUGurates protein synthesis
what does the initial AUG code for in prokaryotes?
what do DNA topoisomerases do?
create a nick in the helix to relieve supercoils
what does primase do?
makes an RNA primer on which DNA polymerase III can initiate replication
what does DNA polymerase III do?
elongates the chain by adding deoxynucleotides to the 3' end until it reaches primer of preceding fragment; 3' -> 5' exonuclease activity proofreads each added nucleotide
what does DNA polymerase I do?
degrades RNA primer with 5' to 3' exonuclease
what does DNA ligase do?
seals DNA
in which direction does DNA polymerase synthesis occur?
5' to 3'
in which direction does proofreading with exonuclease occur?
3' to 5'
after excision repair-specific glycosolase recognizes and removes a damaged base, what does endonuclease do?
makes a break several bases to the 5' side and removes a short stretch of nucleotidse - the n DNA polymerase fills gap and DNA ligase seals it
the 5' of the incoming nucleotide bears what?
the triphosphate/engergy sourse for bond
DNA, RNA, and protein synthesis all occur in what direction
5' to 3'
which is the largest type of RNA?
mRNA (massive)
which is the most abundant type of RNA?
rRNA (rampant)
whihc is the smallest type of RNA
tRNA (tiny)
RNA polymerase I makes what?
RNA polymerase II makes what?
what does RNA polymerase III make?
alpha-amantin, a substance found in death cap mushrooms, inhibits what?
RNA polymerase II
this is the site where RNA polymerase and multiple other transcription factors bind to DNA upstram from gene locus
this is a stretch of DNA that alters gene expression by binding transcription factors
enhancer - may be located close to, far from, or even within (in an intron) teh gene whose expression it regulates
theis is the site where negative regulators (repressors) bind
intervening noncoding segments of DNA are called what?
where are introns spliced out of?
primary mRNA transcripts
these particles facilitate splicing by binding to primary mRNA transcripts and forming spliceosomes
where does RNA processing occur?
what three events occur in RNA processing after transcription?
(1) capping on 5' end (7-methyl-G)
(2) polyadenylation on 3' end (approx 200 A's)
(3) splicing out of introns
what do all tRNAs have at the 3' end?
CCA along with a high percentage of chemically modified bases
in tRNA, the anticodon end is opposite what?
the 3' aminoacyl end
what does a mischarged tRNA do?
reads the usual codon but inserts wrong amino acid
what two things are responsible for the accuracy of amino acid selection?
aminoacyl-tRNA synthetase and binding of charged tRNA to the codon
during protein synthesis, in which site does Met sit?
in the P site - peptidyl
during protein synthesis, where does the incoming amino acid bind?
A site - aminoacyl; hydrolyzes Met's bond to its tRNA while simultaneously forming a peptidyl bond between the 2 amino acids