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DNA, RNA, and Protein

DNA, RNA, and Protein. Replication Transcription Translation. Semi-conservative Replication. Occurs during S phase of cell cycle DNA unwinds, at replication fork, via helicase DNA polymerase makes 2 copies of DNA Complementary base pairing: A=T, G = C

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DNA, RNA, and Protein

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  1. DNA, RNA, and Protein Replication Transcription Translation

  2. Semi-conservative Replication • Occurs during S phase of cell cycle • DNA unwinds, at replication fork, via helicase • DNA polymerase makes 2 copies of DNA • Complementary base pairing: A=T, G=C • A & G are purines; T & C are pyrimidines • Purines are double rings; pyrimidines are single • Leading strand has continuous replication • Lagging strand done in Okazaki fragments • DNA ligase joins fragments on lagging strand

  3. Replication Forks & ORE

  4. Prokaryotic Replication • Prokaryotes have no internal membranes. • They have 1 circular chromosome. • Replication starts at 1 site. • Two replication forks form; replication moves in opposite directions. • Replication continues until forks meet & entire chromosome is copied.

  5. Making copies of DNA • 5’TACCGACTTGATCATTTAGGTAGACATATT…3’ 3’ATGGCTGAACTAGTAAATCCATCTGTATAA…5’ DNA splits into leading (5’) & lagging (3’) strands Each strand does complementary base pairing. • 5’TACCGACTTGATCATTTAGGTAGACATATT …3’ 3’ATGGCTGAACTAGTAAATCCATCTGTATAA …5’ and • 3’ATGGCTGAACTAGTAAATCCATCTGTATAA…5’ 5’TACCGACTTGATCATTTAGGTAGACATATT …3’

  6. Transcription • Makes RNA copy of DNA via RNA polymerase • Makes mRNA, tRNA, or rRNA • RNA polymerase binds to DNA promoter • DNA strands unwind & separate • RNA polymerase adds free RNA nucleotides to complement 1 strand of DNA bases. • G =C; C=G; T=A; A=U • RNA polymerase releases DNA & new RNA when reaches a termination signal.

  7. Transcription & Translation DNA:5’ TACCGACTTGATCATTTAGGTAGACAT…3’ mRNA:AUGGCUGAACUAGUAAAUCCAUCUGUA… • mRNA exits nucleus after processing cap & tail • mRNA on ribosome is translated via tRNAs. • tRNA anticodons pair with mRNA codons (UAA, UAG, UGA). • Each tRNA carries a specific amino acid or a stop signal. • Genetic code is maintained universally. mRNA: AUGGCUGAACUAGUAAAUCCAUCUGUA polypeptide: met-ala-glt-leu-val-ast-pro-ser-val-

  8. Translation • Involves all 3 types of RNA: mRNA, tRNA, rRNA • Produces polypeptides which form proteins • Peptide bonds link amino acids together • There are 20 essential amino acids found in all living things. Some have modifications. • Amino acids form 1o, 2o& 3oprotein structures • Structures are essential to protein function

  9. Steps of Translation • mRNA docks on ribosome. Its 1st codon is AUG • tRNA with met binds via its anticodon UAC. • tRNA with its amino binds to 2nd codon. • Ribosome detaches met from 1st tRNA. • Peptide bond forms between met & 2nd amino acid. • First tRNA exits the ribosome & 3rd tRNA enters. • Elongation continues until reaches stop codon • Ribosome separates from mRNA with last tRNA • Translation machinery then translates same or new mRNA

  10. Human Genome • The entire gene sequence of human DNA • 3.2 billion base pairs in our 23 chromosomes • Use computers to analyze DNA sequences • Bioinformatics , a new field, compares these. • Help predict loci of genes • Don’t know yet what our 30,000 genes encode • Field of proteomics links gene to protein made

  11. Proteomics

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