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What is central dogma? From DNA to Protein

What is central dogma? From DNA to Protein. All proteins consist of polypeptide chains A linear sequence of amino acids Each chain corresponds to the nucleotide base sequence of a gene. What is the first step?.

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What is central dogma? From DNA to Protein

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  1. What is central dogma?From DNA to Protein • All proteins consist of polypeptide chains • A linear sequence of amino acids • Each chain corresponds to the nucleotide base sequence of a gene

  2. What is the first step? 1. Transcription: Enzymes uses base sequence of a gene as template to make strand of RNA • Two DNA strands unwind in a specific region • RNA polymerase assembles strand of RNA • Covalently bonds RNA nucleotides (adenine, guanine, cytosine, uracil) according to nucleotide sequence of exposed gene

  3. What is the second step? • 2. Translation • Information in the RNA strand is decoded (translated) into a sequence of amino acids

  4. Prokaryotes and eukaryotes • In prokaryotic cells (no nucleus) • Transcription and translation occur in cytoplasm • In eukaryotic cells • Genes are transcribed in the nucleus • Resulting mRNA is translated in the cytoplasm

  5. Three types of RNA • Messenger RNA (mRNA) • Carries protein-building codes from DNA to ribosomes • Ribosomal RNA (rRNA) • Forms ribosomes (where polypeptide chains are assembled) • Transfer RNA (tRNA) • Delivers amino acids to ribosomes

  6. RNA and DNA compared • DNA • exists as double-stranded molecules • hereditary information • double helix • contains deoxoyribose sugar • RNA • Disposable copies of hereditary information and some are catalytic • exists as a single stand. • contains ribose instead of deoxyribose • contains uracil in place of thymine

  7. RNA Modification: Alternative Splicing • Before mRNA leaves the nucleus: • Introns are removed • Some exons are removed along with introns; remaining exons are spliced together in different combinations • Poly-A tail is added to 3’ end of new mRNA

  8. What is the genetic code? • Messenger RNA (mRNA) carries DNA’s protein-building information to ribosomes for translation • mRNA’s genetic message is written in codons • Sets of three nucleotides along mRNA strand

  9. Codons • Codonsspecify different amino acids • A few codon signals stop translation • Sixty-four codons constitute a highly conserved genetic code

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