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Transcription - is the first stage of __________________ and happens in the _____________. RNA molecules are produced by copying part of the nucleotide sequence of _____________ into a complementary sequence in RNA, a process called ________________. Transcription requires an enzyme known as _____________________________ that is similar to DNA polymerase. Steps of Transcription: 1. RNA _____________________________ binds to DNA and separates the DNA strands. Unzipping the ___________________________. 2. RNA polymerase will bind to regions of DNA known as promoters, which have specific base sequences. In effect, _________________________ are signals in DNA that indicate to the enzyme where to bind to make RNA 3. RNA _________________________ then uses ___________strand of DNA as a template from which free ______________________ are assembled into a strand of mRNA. 4. Nucleotides will form base pairs - Guanine bonds with ____________________ Adenine bonds with _________________________. (RNA does not have _________________) 5. The transcribing continues until the mRNA reaches a signal on the DNA called a stop codon that cause transcription to stop when the new RNA molecule is completed. 6. The completed mRNA leaves the _______________________________ and travels to the_________________________________ located in the cytoplasm. RNA Editing 1. RNA molecules require editing before they are ready to make proteins. A few, including some of the rRNAmolecules that make up ________________________, are produced from larger RNA molecules that are cut and trimmed to their final sizes. 2. Large pieces are removed from the RNA molecules transcribed from many eukaryotic genes before they become functional. These pieces, known as ___________________ or intervening sequences, are cut out of RNA molecules while they are still in the cell nucleus. 3. The remaining portions, called __________________________, or expressed sequences, are then spliced back together to form the final mRNA. This process is shown below. RNA Editing Many RNA molecules have sections, called introns, edited out of them before they become functional. The remaining pieces, called exons, are spliced together. Then, a cap and tail are added to form the final RNA molecule. Translation The decoding of an mRNA message into a polypeptide chain (protein) is known as translation. Translation takes place on ribosomes. During _________________________, the cell uses information from messenger RNA to produce proteins. Before translation can occur, messenger ______________________ must first be transcribed from ______________________________ in the nucleus and released into the cytoplasm. Translation begins when an mRNA molecule in the cytoplasm attaches to a ________________________________________________ As each ________________ of the mRNA molecule moves through the ribosome, the proper _____________________ acid is brought into the ribosome and attached to the growing polypeptide chain. The _________________does not “know” which amino acid to match to each ________________ That’s the job of transfer RNA. Each ___________________________________ molecule has an amino acid attached to one end and a region of three unpaired bases at the other. The three bases on the ______________________ molecule, called the anticodon, are complementary to one of the mRNA _________________________________ In the case of the tRNA molecule for methionine, the anticodon ____________________ are UAC, which pair with the methionine codon, ____________________. The ribosome has a second binding site for a ________________________________molecule for the next codon. If that next codon is UUC, a tRNA molecule with an _________________________anticodon would fit against the mRNA molecule held in the ribosome. That second tRNA molecule would bring the amino acid phenylalanine into the ribosome. Like an assembly line worker who attaches one part to another, the ribosome forms a ________________ bond between the first and second amino acids, methionine and phenylalanine. At the same time, the ribosome breaks the bond that had held the first ___________________________ molecule to its amino acid and releases the tRNA molecule. The ribosome then moves to the third ______________________, where a tRNA molecule brings it the amino acid specified by the third codon. The polypeptide chain continues to grow until the ribosome reaches a stop _________________ on the mRNA molecule. When the ribosome reaches a stop codon, it releases the newly formed ___________________________and the mRNA molecule, completing the process of _________________________________ The Genetic Code 1. Proteins are made by joining amino acids into long chains called ______________________ Each polypeptide contains a combination of any or all of the 20 different _________________. The properties of proteins are determined by the order in which different _______________ acids are joined together to produce ____________ 2. The “language” of mRNA instructions is called the ________________code. 3. RNA contains four different bases: ______________, __________________, ______________, and __________________. The genetic code is read three letters at a time, so that each “word” of the coded message is _________bases long. Each three-letter “word” in mRNA is known as a codon,. 4. A _______________ consists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide. For example, consider the following RNA sequence: UCGCACGGU This sequence would be read three bases at a time as: UCG-CAC-GGU The codons represent the different amino acids: UCG-CAC-GGU Serine-Histidine-Glycine Codons A codon is a group of three nucleotides on messenger RNA that specify a particular amino acid. Because there are four different bases, there are 64 possible three-base codons (4 × 4 × 4 = 64). 61 are codons for amino acids. There is also one codon, AUG, that can either specify methionine or serve as the initiation, or “_________________" codon for protein synthesis. there are three “stop” codons that do not code for any amino acid. _______________ codons act like the period at the end of a sentence; they signify the end of a polypeptide.