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25 Cards in this Set

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What is meant by the semiconservative model?
Semiconservative
– new DNA contains one parent strand and
one daughter strand
how are DNA strands held together?
hydrogen bonds
what happens at the replicating fork?
At this point replication occurs. As th replication fork moves along the parental strand DNA each of the unwound single strands combines with new nucleotides
Leading stand?
One new strand that is synthesized continuously as the DNA polymerase moves toward the replication fork.
Lagging stand?
new DNA strand that is synthesized in pieces as the DNA polymerase moves away from the replication fork.
structure of DNA?
FOUR BASES A.T.C.G
PHOSPATE.HYDROGEN BOND. DEOXYRIBOSE SUGAR
enzymes involved in replication
DNA Polymerase
• Synthesizes a new strand; old strand is the
template
• Multiple types (5 in E. coli; 7 in Eukaryotes)
• Two distinct characteristics
– cannot start a strand from scratch
– only add to the 3’ end of existing strand
14
The Reaction:
dNTPs - deoxynculeoside
triphosphates
Figure 16.12 15
Helicase
• Untwists the double helix and separates
the two parent strands
• SSBP hold strands apart
– single-strand binding proteins
what is a gene?
• “A discrete unit of hereditary information
consisting of a specifific nucleotide sequence
in DNA”
• Relationship
transcription?
what is requires
the synthesis of a complemenary strand of RNA from a DNA template.
- RNA polymerase and a supply of RNA nucleotides
- RNA pol. will bind to dna at the promoter
- it will assemble free nucleotides inot a new chain
- as the chain grows, RNA pol. moves along DNA
- RNA synthesis continues until RNA pol. reaches a terminator and when this happens the new single-stranded mRNA and the RNA pol. are released from the DNA.
mMRNA
it carries the codeed info for making specific proteins form DNA to ribosomes, where proteins are synthesized
Translation?
involves the decoding of nucleic acids and converting that info into proteins
degeneracy of the code means?
there are 64 possible codons but only 20 amino acids which means that amino acids are signaled by several alternative codons
sense codons? nonsense codons?
-code for amino acids
-do not code for amino acids
tRNA
along with the ribosome(the site of translation)it will recognize the specific codons and transport the required amino acids.
anitcodon?
a sequence of three bases that are complementary to a codon
details in translation?
2 rib.subuntits and mRNA + protein factors assemble--)initiator AUG condon is set up--)1st tRNA binds to the start codon, bringing with it the amino acid methionine--)trna recognizes the 2nd codon+ moves it into position on the ribosome--)ribosome joins the a.a. w/ the peptide bond, and the trna mole. leaves the ribosome--)the ribosome then moves along mrna to the next codon--)as the proper a.a. are put in line one by one and peptide bonds form b/w them and polypeptide chain results--)translation will end
importance of the promoter?
-DNA sequence that RNA
polymerase attaches to and
initiates transcription
a-lso regulates how much
transcription will occur
- where transcrition begins
In Prokaryotes
- 10 bp upstream of initiation site
– RNA polymerase recognizes and binds
directly to DNA
what direction is RNA synthesized?
- New RNA is made in 5’ to 3’ direction
– Enzyme adds to 3’ end of growing strand
what is the coding, template and complementary strands, and the mRna strand?
the coding strand is exactly the mRNA strand with replacing T as U.
the TEMPLATE strand is the complementary strand.
function of rRNA?
molecules that combine with ribosomal polypetides to form ribosomes
in bacteria what is needed for RNA polmerase to recognize the promoter?
a sigma factor is needed
where does RNA TC begin?
10 nucleotides away from the promoter.
what happens during the tc of the 1st 10 nucleotides?
Rna polymerase will release its sigma factor causing it to adhere tighter to the DNA.
ways RNA polymerase differs from DNA polymerase?
RNA polymerase:
- unwinds and opens DNA by itself; helicase not required
- proceeds slower
- incorporates ribonucleotides instead of deoxyribonucleotides
-uracil instead of thymine
-lacks proof-reading function, leaving base pair error about every 10,00 nucleotides
what is the difference b/w promoter seq. and an origin?
a promoter= a DNA seq. that initiates tc
a origin=pt where replication begins