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Class 10: Transcription

SBI4U Molecular Genetics. Class 10: Transcription. From Friday…. What is the Central Dogma?. Central Dogma. Fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins. Why is gene expression important?.

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Class 10: Transcription

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  1. SBI4U Molecular Genetics Class 10: Transcription

  2. From Friday…

  3. What is the Central Dogma?

  4. Central Dogma Fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins

  5. Why is gene expression important?

  6. The Genetic Language Uses 4 Letters Written Into 3-Letter Words

  7. What will be the chain of Amino Acids for the following mRNA sequence? AUGUGCAACCGUCGAUAG

  8. Today we are going to talk about… TRANSLATION

  9. Introduction • During transcription the DNA code is chemically rewritten as an RNA code • Transcription: divided into 3 sequential stages • 1. Initiation • 2. Elongation • Termination

  10. Initiation • In prokaryotes and eukaryotes begins with RNA polymerase • Binds to the DNA strand, unwinds the helix near thebeginning of a gene • The binding occurs at the promoter which is a nucleotide sequence that lies just before the gene • A key to the promoter sequence in the eukaryotes is TATA box

  11. TATA Box • A region of the DNA with high percentage of TA bases, which is recognized by the RNA polymerase • Prokaryotes have a TATAAT sequence • A and T because 2 hydrogen bonds, less energy needed to break RNA expends less energy • The part of the gene that is transcribedinto RNA is called the Transcription Unit

  12. Elongation • No primer needed 5’ to 3’ direction • The opposite strand of DNA is known as the coding strand, it contains the same base pair sequence as the new RNA • RNA elongates as nucleotides are added one at a time • The new RNA molecule winds temporarily with template DNA into hydrid RNA/DNA double helix

  13. Elongation Continued.. • Beyond this region RNA unwinds from DNA • When a cell requires a particular protein they need to produce thousands or even millions of copies example. • A single red blood cell contains 375 million hemoglobin molecules

  14. Termination • Transcription is terminated when RNA polymerase recognizes the termination sequence • In prokaryotes 1 termination mechanism involves a protein binding to the mRNA and stopping transcription or when mRNA binds with itself in a hairpin loop • In eukaryotes 1 termination is string of A • The newly made RNA descoiatates from the DNA template

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