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36 Cards in this Set

  • Front
  • Back
semiconservative method
two copies of the original DNA contain one new strand and one original strand
Meselson experiment
used heavy and light nitrogen isotopes to discover that DNA replicated and combined using the semiconservative method
3 steps of replication
1. initiation
2. elongation
3. termination
initiation of replication
1. at oriC DnaA - replication initiator protein- recruits DnaB (helicase) and DnaC (helicase loader) to unwind DNA bidirectionally
2. replication fork appears at either end of the replication bubble
3. DNA primase and RNA polymerase make primers
elongation replication
synthesizes complementary base pairs to create an exact copy of the template
1. DNA poly III elongates the existing primers in 5' --> 3'
2. lagging strand v leading strand
3. Okazaki fragments are linked together by DNA ligase
4. DNA poly I replaces RNA primer with DNA
5. RNAse H removes RNA primers of Okazaki fragments
replisome
stationary complex that stays stationary relative to the DNA (which is moving); exhibit rotational symmetry; there is one at both forks
termination replication
ends replication process by separating DNA molecules; topoisomerase IV; terminus located roughly opposite oriC
DNA polymerase III
1. proofreading/self correcting
2. adds bases 5'-->3'
3. elongates new strand
4. can't ADD nucleotides together, only extend chain
5. dehydrates Hbonds between 3' OH group and alpha phosphate
topioisomerases
induce supercoiling of DNA
type 1 topioisomerases
remove negative supercoils
type II topioisomerases
introduce negative supercoils
differences between RNA and DNA
1. sugars: RNA (ribose) DNA (deoxyribose)
2. nitrogenous bases: RNA (uracil) DNA (thymine)
3. structure: RNA (single stranded; short) DNA (double stranded; very long)
4. stability: RNA (unstable) DNA (stable)
RNA polymerase (RNAP)
1. key transcription enzyme
2. synthesizes from DNA template
3. synthesizes RNA from 5'-->3'
4. does not require a primer
steps of transcription
1. initiation
2. elongation
3. termination
initiation of transcription
1. sigma factor binds to core RNAP
2. holoenzyme seeks out promotor region (Pribnow box and consensus region)
3. holoenzyme binds to promotor, forms closed complex
4. mRNA synthesis occurs, sigma factor leaves
5. DNA opens, forming open complex
elongation of transcription
1. mRNA synthesized until reaches termination signal on DNA
2. ribosomes bind to mRNA and begin translation
termination of transcription
1. rho-dependent (site on mRNA attracts termination rho factor)
2. rho-independent (stem-loop structure forms)
3. exit channel (crevice in RNAP where mRNA exits once its snythesized)
sigma factor
transcription initiation factors that recognizes promoter sequences
translation
RNA directed synthesis of protein
translation process
1. requires many ribosomes
2. occurs simultaneously with transcription and replication
3. ribosomes bind at 5' end; ribosomes will then slide down to 3' end as translation continues
genetic code conclusions
1. redundant
2. a amino acid is specified by 3 bases
3. commaless
4. requires other features to stop/start protein synthesis
how many bases needed to specify an amino acid and why?
1. 3
2. because there will be 64 possible amino acids, compared to just 16 and 4 aa if only 2 and 1 were required respectively
3. there are 20 known amino acids
how did they determine that 3 bases specify an amino acid?
1. conducted commaless test
2. 1 base removed/added = didn't proceed
3. 1 base removed and 1 added = proceeded normally
4. 3 bases added = proceed normally
tRNA
1. transfers aa to polypeptide chain growing at ribosome during translation
2. 3' acceptor end/stem - aa is bound (always have same CCA)
3. anticodon loop - where anticodon is bound
anticodon
3 bases complementary to codons
initiation translation
ribosome is assembled onto the RNA transcript
1. 30S ribosome looks for RBS and AUG sequence (start codon)
2. once 30S binds to transcript, 50S binds to 30S forming 70S
elongation translation
polypeptide chain is extended as RNA transcript is read and aa added
termination translation
polypeptide synthesis is stoped
1. terminates at stop codon
DNA in transcription =
= RNA translation
RNA in transcription =
= protein in translation
NTPs in transcription =
= amino acids in translation
RNAP in transcription =
= ribosomes in translation
promoter in transcription =
= RBS in translation
start site in transcription =
= start codon in translation
termination site in transcription =
= stop codon in translation
operon
group of genes that share one promoter and one terminator transcription regions; not eukaryotes