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Discover Protein Synthesis through Transcription and Translation processes. Learn how DNA converts to RNA to create proteins. Explore the roles of mRNA, rRNA, and tRNA in building proteins.
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Introduction - Transcription • Ever play skee ball at an arcade before? • If you have, then you realize the need to exchange quarters for tokens before you can use them. • Just like converting quarters to tokens, DNA must convert to RNA before proteins can be made.
Transcription • Transcription – Process of copying a sequence of DNA to produce a complementary strand of RNA.
Central Dogma Involves three processes: • Replication – DNA replicates • Transcription – DNA converts to RNA • Translation – RNA interpreted for proteins • Pg 225, Figure 4.1 • Francis Crick
RNA • RNA stands for ribonucleic acid • Like DNA, RNA is also a chain of nucleotides, each made of a sugar, phosphate group, and nitrogen containing base.
RNA Polymerase • Just like DNA polymerase binds nucleotides to make new DNA… • RNA polymerase binds nucleotides together to make new RNA!!!
Transcription • 1) RNA polymerase and other proteins begin to unwind DNA • 2) RNA polymerase uses one strand of DNA as a template to string together a complementary strand of RNA nucleotides. The RNA strand hangs freely as DNA zips back together. • 3) The RNA strand detaches from the DNA once the entire gene has been transcribed. • Pg 227, figure 4.2
Types of RNA • Messenger RNA (mRNA) – Intermediate message that is translated to form a protein. • Ribosomal RNA (rRNA) – Forms part of ribosome (the cell’s protein factory). • Transfer RNA (tRNA) – Brings amino acids from the cytoplasm to ribosome to help make the growing protein.
Translation • Translation – The process that converts, or translates, an mRNA message into a polypeptide. • One or more polypeptides make up a protein.
Introduction - Translation • Ever hear of a translator? • Translators translate language (for example, Spanish to English) • In translation, the RNA’s message is translated to make amino acids. • Amino acids are the building blocks of protein.
Codons • Codon – A three nucleotide sequence that codes for an amino acid. • Example: AUG, CUU, AGCall of these are codons
mRNA • mRNA stands for “messenger RNA” • mRNA carries instructions of DNA from the nucleus to the cytoplasm as well as reads sets of codons.
Stop & Start Codons • Start Codon – AUG; signals the start of translation. • Stop Codons – UAA, UAG, UGA; signals the end of an amino acid chain.
Protein Synthesis • In protein synthesis, tRNA translates mRNA to create three-piece codons. • Proteins are synthesized as a result when the STOP codon is reached in the translation.