dna in the cell stored in number of chromosomes (24 in human genome) tightly coiled threads of dna...
TRANSCRIPT
DNA in the Cell
• Stored in Number of Chromosomes (24 in Human Genome)
• Tightly coiled threads of DNA and Associated Proteins: Chromatin
• 3 billion bp in Human Genome: Total genetic content of cell
• DNA can be replicated
• Genes: Specific sequence of bases (one polypeptide
Central Dogma
Flow of Information
• DNA store a lot of information
• A little bit used at a time
• Small bits copied into temporary molecules
• messenger RNA (mRNA)
• Transcription
• RNA - Single Stranded– U for T– Ribose is sugar
Coding
• Sets of three letter from (A,G,C,T) codes for amino acid (codon)
• Stop codons (3)
• Universal language for Amino Acids
Transcription
• Transcription to preserve the DNA (sense)
• RNA (antisense) made by RNA Polymerase
• Polymerase binds at DNA promoter sequence just before the gene
• Nucleotides from environment added to RNA chain based on DNA Template
• Continues until terminator sequence
Genes
• 10% of DNA encodes for Genes
• Exons: Coding Sequences for Proteins
• Introns: Non-Coding Sequences
• Human Genome: 100,000 Genes
• 100,000 Proteins synthesized from genes
• Genes encode for Amino Acids(Codons)
• Building blocks for proteins (workers)
• DNA to messenger RNA (mRNA)
• Direct for prokaryotes
• From Nucleus to Cytoplasm for eukaryotes
• Introns removed from mRNA
• Template for Protein Synthesis by Ribosome
Translation
• mRNA copy to Protein
• Translation: Process of Protein Synthesis
• Occurs on Ribosomes: Large structures consisting of proteins and RNA
• Many of them in the cell
• transfer RNA (tRNA) which accomplish actual translation
tRNA
• At one anticodon (three base sequence)• Complementary to one of codons on mRNA• At other end is a chemical group to attach an
amino acid• Read codons, Bind to them, Bring amino acid
to ribosome• Shape dependent -- Energy Consuming (50%
in bacteria)
Signals for Protein Synthesis
• Stop Codons• Start Codon
– Beginning of mRNA sequence– Reading Frame (way message divided into
codons)
• AUGCCUGUCAAA• AUG CCU GUC AAA• A UGC CUG UCA AA
DNA Replication
• Copy DNA for new cells
• DNA Polymerases
• Mistakes corrected by enzyme itself
• Proofreading
• Mistake 1 in 10^9