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12-3 Protein Synthesis

12-3 Protein Synthesis. Double stranded Sugar = deoxyribose Thymine (no Uracil) Stays in nucleus One type Same copy in the cell all the time. Single stranded Sugar = ribose Uracil (instead of Thymine) Nucleus & cytoplasm 3 types (mRNA, tRNA, rRNA) Disposable copies. DNA vs. RNA.

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12-3 Protein Synthesis

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  1. 12-3 Protein Synthesis

  2. Double stranded Sugar = deoxyribose Thymine (no Uracil) Stays in nucleus One type Same copy in the cell all the time Single stranded Sugar = ribose Uracil (instead of Thymine) Nucleus & cytoplasm 3 types (mRNA, tRNA, rRNA) Disposable copies DNA vs. RNA

  3. Ribose vs. Deoxyribose

  4. RNA • many functions but mostly just protein synthesis • three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA

  5. Types of RNA

  6. mRNA • RNA molecules that carry copies of the DNA instructions = mRNA • messenger RNA (mRNA) = serve as “messengers” from DNA to the rest of the cell

  7. rRNA • Ribosomes are made up of several dozen proteins, as well as a form of RNA known as ribosomal RNA (rRNA).

  8. tRNA • During the construction of a protein, a third type of RNA molecule transfers each amino acid to the ribosome • as specified by coded messages in mRNA. • These RNA molecules are known as transfer RNA (tRNA).

  9. Transcription (DNA  mRNA) • RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA • required enzyme = RNA polymerase • RNA polymerase binds to DNA (in nucleus) • separates the DNA strands • RNA polymerase then uses one strand of DNA as a template • nucleotides are assembled into a strand of mRNA

  10. Where does RNA start? • enzyme will bind only to regions of DNA known as promoters • promoters are signals in DNA that indicate to the enzyme where to bind to make RNA (“start sequence”). • Similar signals in DNA cause transcription to stop when the new RNA molecule is completed.

  11. The “language” of mRNA instructions is called the genetic code • RNA contains four different bases: A, U, C, and G • Letters read “3” at a time = codon • Codon = a group of three nucleotides on messenger RNA that specify a particular amino acid.

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