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DNA (Enzymes (Helicase untwist strands, Single-strand binding protein bind…
DNA
Enzymes
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Single-strand binding protein bind to strands, preventing from repairing
Topoisomerase break, swivel, rejoin strands
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Transcription
Synthesizing RNA using DNA
Nucleic Acids are transcribed from DNA to RNA
mRNA carries genetic info from DNA to get synthesized
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Stages of Transcription
Initiation
RNA polymerase binds in a certain location and decides where transcription starts and which strand is template
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Termination
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Eukaryotes
RNA Polymerase 2 transcribes polyadenylation signal sequence
that specifies AAUAAA in pre-mRNA
Binds to proteins in the nucleus and cuts RNA transcript from RNA polymerase
RNA Polymerase 2 transcribes starting at 5' end
Promotor: Where RNA polymerase attaches and starts transcribing
Terminator: Signals end of transcription
RNA Processing
RNA splicing
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Avg length of transcription in human DNA is 27,000 pairs
Avg protein of 400 amino acids needs 1,200 pairs to code
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RNA Polymerase 2 transcribes introns and eons from DNA
Introns are cut from molecule and exons joined together
Spliceosome binds to nucleotides along intron. Intron is released and spliceosome joins 3 exons
RNA's in spliceosome catalyze splicing reaction
Alteration
5' end of pre-mRNA synthesized and receives 5' cap
At 3' end, an enzyme adds A nucleotides to form a poly-A tail
5' cap and poly-A gal help export mRNA from the nucleus, protect mRNA from degrading with hydrolytic enzymes, and help ribosomes attach to 5' end
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Translation
tRNA
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Binds to an mRNA codon and translates into an amino acid
Then carries that amino acid to the ribosome
Aminoacyl-tRNA synthetases Enzyme that matches tRNA up with amino acid
One synthetase for each amino acid
Catalyzes covalent bond of amino acid to tRNA by hydrolyzing ATP
Results in a charged tRNA
Ribosomes
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Each ribosome has 3 binding sites for tRNA
P site holds tRNA carrying polypeptide chain
A site holds tRNA carrying amino acid about to be added
E site where tRNA's leave the ribosome
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Elongation
Anticodon of tRNA pairs with mRNA in A site
rRNA catalyzes formation of peptide bond between amino group and carboxyl end
This removes tRNA in P site and attaches to amino acid in A site
Ribosome translocates tRNA in A site to P site and empty tRNA in P site is moved to E site
Termination
Elongation stops when stop codon reaches A site
UAG, UAA, UGA signal to stop translation
Release factor adds water instead of amino acid to chain and breaks bond between polypeptide and tRNA in P site
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DNA
Nitrogenous bases, deoxyribose, a phosphate group
Looped around histones, that combined become a chromosome
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DNA is nucleotides, deoxyribose, and phosphate group
Reason for diversity in species
Different species had more of a certain base
Helical made of 2 nucleotide strands held by covalent bond
Sugar and phosphate connected by nitrogen base rungs
Bases .34nm apart, full turn every 3.4nm
A + G are purines (two organic rings)
C + T are pyrimidines (single ring)
A pairs with T : G pairs with C
Griffith killed pathogenic and combined with nonpathogenic and some became pathogenic
Pathogenicity was inherited
First called transformation but now known as change in geno+phenotype
E.coli infected with labeled protein and DNA
DNA was found inside cells that now released phages but protein wasn't
DNA is genetic material of T2
Chains unwind and each replicates itself
Since each base can only pair with one other base, each strand is a template for complimentary stand
DNA initiation proteins attach to DNA and separate strands opening replication bubble
At end of bubble is replication fork that unwinds DNA
Strands are elongated with DNA polymerase