Unit 3 Flashcards
nonsense mutation
causes premature stop codon
nonconservative
single nucleotide replaced resulting in a change in amino acid and chemical property(ie. polar to non polar)
conservative
single nucleotide resulting in amino acid change but chemical properties remain the same(ie. basic to basic)
silent
change in single base but amino acid is the same
DNA Proofreading
base paired wrong, fix single nucleotide error in the sequence during synthesis; cuts nucleotide off and base is added back in
Mismatch pair
same error as Proofreading but is fixed after synthesis; chunk is removed and polymers comes back and fixes it; ligase fills gap
Excision Repair
from Uv damage, two types
Base excision repair
takes put single base, polymerase fills it and ligase seals it
Nucleotide Excision Repair
base and backbone damaged; fills gap and links pieces
Purpose of DNA synthesis
make new DNA
Primase
synthesizes RNA primer; synthesis of a short RNA strand that is complementary to single-stranded DNA
Helicase
unzips DNA
Topoisomerase
untwists and relieves pressure
SSBP
binds to single strand to keep. them apart
ligase
joins strands back together
telomerase
adds DNA to make up for loss in replication; maintains chromosome
template strand
used as direct template for mRNA
coding strand
commentary to template strand; same as mRNA strand
Purpose of transcription
make RNA copy of DNA
Purpose of translation
turn mRNA into a protein
tRNA
carries amino acid to ribosome
initiation
mRNA enter ribosome at A site bind to start codon in P site; translation begins
elongation
aminoacyl tRNA moves into A site- Anticodon binds to codon; peptide bond forms with amino acid in P site; translocation
translocation
ribosome moves a codon over after peptide forms between tRNA in the A and P site
termination
ribosome reaches stop codon and release factors trigger hydrolysis of bond between tRNA and Polypeptide chain; subunits separate
A-site
where tRNA initially binds to mRNA
P-site
tRNA attaches to polypeptide chain and amino acid is transferred
E-site
uncharged tRNA exits ribosome
tRNA synthetase
ensures that tRNA binds to correct amino acid based on anticodon sequence
DNA polymerase
replicates DNA by adding nucleotides; hand-like orientation allows it to “grab on to” DNA
Synthesis of Okazaki Fragments
5’–> 3’ using lagging strand template;
Replication of the linear ends of eukaryotic chromosomes results in an unreplicated end due to:
Primer is degraded on the lagging strand and synthesis of the final base pairs cannot proceed
Primary Structure of Nuclliec Acid
Phosphodiester bonds form between phosphate of one base to the sugar of another; nucleotide sequence determine structure
Antiparallel Orientation
DNA strands run opposite of each other; 5’ of one orients with 3’ of the other
Polymerization of nucleic acids occurs by _________reaction that forms ________ bonds.
condensation; Phosphodiester
True or False: Okazaki fragments would be unnecessary if DNA polymerase could synthesize DNA in both the 5’ and 3’ directions.
True
release factor
binds to stop codon in A-site triggers release of polypeptide chain
CCA
where amino acid attaches to tRNA
Splicing
introns are removed from RNA strand in transcription
Where is the start codon located?
at the downstream end of the 5’ untranslated region (UTR)
Bacterial RNA polymerase
synthesizes RNA
frame shift mutation
insertion/deletion of a nucleotide so that the reading frame shift
T/F: Both frameshift and point mutations can occur in any DNA sequence.
False
True or False: The lac operon is transcribed at the highest rate when extracellular glucose and lactose are abundant.
False
alternative splicing
removes/excludes exons
LAC operon
works when there’s no glucose to breakdown lactose
Proximal Promoter
binds to gene-specific transcription factors; control initiation of transcription
Transcription factors
bind to DNA to regulate transcription
TRP
acts as co-repressor; binds to TRP repressor and inhibits transcription; difficult to make so don’t usually use
Decondonsed chromatin
accesible
condensed
inaccesible
What regulation do
bacteria employ?
Allosteric
chromatin
complex on DNA and proteins
True or False: The repressor protein is bound to DNA of the operator when lactose is present.
false
Purines
adenine and guanine
Pyrimidines; 9 atoms
cytosine, uracil, thymine; 6 atoms
Number of hydrogen bonds between A and T
2
Number of bonds between C and G
3 bonds
Why is RNA versatile?
single stranded; can catalyze chemical reactions
Role of RNA
expression; easy access and DNA is to stable
Ribozyme
RNA as an enzyme
Sliding Clamp
holds DNA polymerase in place
Hersey Chase Experiment
DNA is genetic material
Semiconservative(Nelson-Stahl)
strands separate and become template; made of one new and one old
Start of DNA synthesis in bacteria
Bubble opens up
Replication Fork
bubble opens; strands separate and proteins bind
solution for lagging strand
small segments(ozaki fragments) allow for lagging strand to be read in 5’ –>3’
Central Dogma of Biology
DNA codes for RNA, RNA codes for proteins
Where does translation occur?
Ribosomes in the cytoplasm
Where does transcription take place?
nucleus
genotype
determined by bases
phenotype
what’s expressed
Genetic code is redundant bc …
allows for errors-code for same amino acids
genetic code is Unambiguous
never more than one amino acid per codon
genetic code is universal
same in all organisms
conservative
amino acids with similar properties are encoded by similar ones
missense
changes in amino acid
chromosomal deltion
loss of genes
chromosomal inversion
backwards
chromosomal duplication
additional copies of chromosome segment
chromosomal translocation
piece breaks off and fuses to another chromosome
+1 site on DNA
first nucleotide to be transcribed
promoter
sequence where RNA polymerase binds to begin transcriptions
TATA Box
identify start of transcription; binding site for RNA polymerase
exon
final mRNA; expressed
intron
primary transcript not in mRNA
What does transcription synthesize?
non-template/coding strand
What does DNA synthesis synthesize?
leading or lagging stand
Transcription Initiation in Bacteria
sigma binds to promoter and twists so transcription can start; allows polymerase to bind
Sigma
bacterial initiator of transcription
5’ cap
add to finshed mRNA to make it mature and ready for transcription: protection
Poly (A) Tail
added to 3’ end of mRNA to stabilize it
Splicisome
removes non-coding segments from pre-mRNA: removes introns: post-transcriptional
Transcriptional Control
regulatory proteins affect ability of RNA polymerase to bind to promoter; transcription can’t start
Translational control
regulatory molecules alter amount of time and mRNA survives or affect one of the processes
Posttranslational Control
chemical modification
Negative control
inhibit expression
Positive control
promote expression
LAC operon repressor
binds to DNA and prevents transcription
Lactose effect on LAC operon
induces by binding to repressor; changes its shape and repressor comes off
CAP effect on LAC operon
signals regarding availability of glucose and lactose
Permase
facilities transport of lactose into bacterial cell; lactose turn off/on the LAC operon
Structure of Chromatin
DNA wrapped around proteins(histones)
activators
increase rate of transcription of target genes
repressors
inhibit/reduce transcription of specific region of genes
Chromatin Remolding
change structure of DNA to allow access for DNA transcription
RNA Processing
capping and splicing
Histones
provide structure for DNA wrapping
nucleosome
histones on string of DNA
Heterochormatin
condensed
uchromatin
uncondensed/unwrapped
DNA methylation
add methyl group, enzymes recognize and condense DNA
Histone Modification: Acetylation
lysine added, becomes (-),(-) pair with DNA so DNA opens
Histone Modification: Phosphorylation
opens DNA; phosphate is (-)
chromatin remolding complex
open DNA by moving nucleosome
Epigentic
environmental changes(reversible)- inheritable- can be good or bad
operons
cluster of genes controlled by one set of regulatory mechanisms; regulated by presence of nutrient; inducible and repressible
Inducer Exclusion
glucose blocks transport of other sugars like lactose
