DNA Synthesis (Replication) Helicase – Separates parental DNA strands (unwind double helix)
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Processes of Nucleic Acids September 17 & 18, 2012 DNA Synthesis (Replication) 1.Helicase – Separates parental DNA strands (unwind double helix) 2.ssB (single-stranded Binding) proteins – Prevents single strands from re-associating 3.RNA Primase – Synthesizes RNA primers, required to initiate DNA nucleotide insertion 4.DNA Polymerase III – Responsible for synthesis of lagging strand & leading strand 5.DNA Pol I – Removes RNA primers & Fills lagging strand gaps (Exonuclease Activity) 6.DNA Ligase – Forms Phosphodiester bond joining 2 adjacent DNA strands
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DNA Synthesis (Replication) Helicase – Separates parental DNA strands (unwind double helix) ssB (single-stranded Binding) proteins – Prevents single strands from re-associating RNA Primase – Synthesizes RNA primers, required to initiate DNA nucleotide insertion - PowerPoint PPT Presentation
Transcript of DNA Synthesis (Replication) Helicase – Separates parental DNA strands (unwind double helix)
Processes of Nucleic Acids September 17 & 18, 2012
DNA Synthesis (Replication)1. Helicase – Separates parental DNA strands (unwind double
helix)2. ssB (single-stranded Binding) proteins – Prevents single
strands from re-associating3. RNA Primase – Synthesizes RNA primers, required to initiate
DNA nucleotide insertion4. DNA Polymerase III – Responsible for synthesis of lagging
strand & leading strand5. DNA Pol I – Removes RNA primers & Fills lagging strand gaps
(Exonuclease Activity)6. DNA Ligase – Forms Phosphodiester bond joining 2 adjacent
DNA strands
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
rRNA (Ribosomal RNA) – in nucleolus gives rise to ribosomal precursors; makes Ribosome, and is the central component of the Ribosome’s protein-manufacturing machinery.
Processes of Nucleic Acids September 17 & 18, 2012
mRNA (Messenger RNA) - encodes chemical "blueprint" for protein (The Genetic Code); carries coding information from Nucleus to Ribosomes (sites of protein synthesis).
Details of mRNA: Encoded in sequence of nucleotides (AUCG),
which are arranged into codons consisting of three bases each
Each codon encodes a specific amino acid, except the stop codons
Stop codons terminate protein synthesis
Processes of Nucleic Acids September 17 & 18, 2012
tRNA (Transfer RNA) - adaptor molecule composed of RNA used to bridge the genetic code (AUCG) in mRNA with the twenty amino-acids code in proteins.
Details of tRNA: The role of tRNA is to specify which sequence from the genetic
code corresponds to which amino acid One end of the tRNA complements the genetic code in a three-
nucleotide sequence called the anticodon On the other end of the tRNA is a covalent attachment to the amino
acid that corresponds to the anticodon sequence Each type of tRNA molecule can be attached to only one type of
amino acid o The genetic code contains multiple codons that specify the same amino
acid; therefore, there are many tRNA molecules, each bearing a different anticodon, which also carry the same amino acid.
Processes of Nucleic Acids September 17 & 18, 2012
*Baking a Cake Analogy
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Translation*AUG (Methionine) – Start Codon *UAG, UGA, UAA – Stop Codons
Processes of Nucleic Acids September 17 & 18, 2012
Initiation: Binding of mRNA to small ribosomal subunit
containing tRNAimet
mRNA is scanned for AUG start codon First amino acid is Methionine
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Elongation: Met-tRNAi already bound to (P) site
1.mRNA codon in (A) site determines which aminoacyl-tRNA binds to (A) site
2.Methionine binds (peptide bond) to aminoacyl1 at (A) site
3.Methionine & aminoacyl1 translocate to (A) site, which now is (P) site – freeing (A) site for a new aminoacyl-tRNA
Steps 1-3 repeat until termination
Processes of Nucleic Acids September 17 & 18, 2012
Processes of Nucleic Acids September 17 & 18, 2012
Termination: A termination (stop) codon is placed into the (A)
site on the ribosomea)UAG, UGA, UAAb)There are NO tRNA anticodons that bind
Stop Codons Release Factors (RF) bind to ribosome Newly peptide chain is released from ribosome
Processes of Nucleic Acids September 17 & 18, 2012
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