Rna and protein synthesis
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Rna and protein synthesis






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Rna and protein synthesis Rna and protein synthesis Presentation Transcript

  • RNA and Protein Synthesis Section 12–3This section describes RNA and its role in transcription and translation.
  • The Structure of RNAList the three main differences between RNA and DNA. 1. RNA has ribose sugar instead of deoxyribose. 2. RNA is generally single-stranded, instead of double-stranded. 3.RNA contains uracil in place of thymine.
  • Purpose of RNAIs the following sentence true or false?► RNA is like a disposable copy of a DNA segment.► True
  • What is the importance of the cell’s ability to copy a single DNA sequence into RNA?► It makes it possible for a single gene to produce large numbers of RNA molecules.
  • Types of RNA What is the one job in which most RNA molecules are involved?► Most are involved in protein synthesis.
  • Types of RNA► Complete the compare-and-contrast table about the types of RNA.
  • Type Function• Carries copies of the instructions for assembling amino acids from DNA to the rest of the cell.• Ribosomal RNA is a part of ribosomes.• Transfer RNA Transfers each amino acid to the ribosome to help assemble proteins
  • TranscriptionCircle the letter of each sentence that is true about transcription.• b. RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA.• c. RNA polymerase binds only to DNA promoters, which have specific base sequences.
  • RNA Editing► Many RNA molecules from eukaryotic genes have sections, called _____, edited out of them before they become functional. The remaining pieces, called, _________are spliced together.► Introns► Exons
  • RNA EditingIs the following sentence true or false?► RNA editing occurs in the cytoplasm of the cell.► False
  • RNA Editing What are two explanations for why some RNA molecules are cut and spliced?► It makes it possible for a single gene to produce several different forms of RNA.► It may play a role in evolution, making it possible for small changes in DNA to have dramatic effects in gene expression.
  • The Genetic CodeProteins are made by joining ________into long chains called polypeptides.► Amino acids
  • The Genetic Code► How can only four bases in RNA carry instructions for 20 different amino acids?► The genetic code is read three letters at a time, so that each “word” of the coded message is three bases long.
  • The Genetic CodeWhat is a codon?► It consists of three consecutive nucleotides that specify a single amino acid that is to be added to a polypeptide.
  • The Genetic Code Circle the letter of the number of possible three-base codons.• 4• 12c. 64d. 128
  • The Genetic Code Is the following sentence true or false?• All amino acids are specified by only one codon.► False
  • The Genetic CodeCircle the letter of the codon that serves as the “start” codon for protein synthesis.a.UGAb.UAAc. UAGd. AUG
  • TranslationWhat occurs during the process of translation?► The cell uses information from messenger RNA to produce proteins.
  • Where does translation take place?► Translation takes place on the ribosomes.
  • Circle the letter of each sentence that is true about translation.► Before translation occurs, messenger RNA is transcribed from DNA in the nucleus.► It is the job of transfer RNA to bring the proper amino acid into the ribosome to be attached to the growing peptide chain.► When the ribosome reaches a stop codon, it releases the newly formed polypeptide and the mRNA molecule.
  • What is an anticodon?► The three bases on a tRNA molecule that are complementary to one of the mRNA codons.
  • The Roles of RNA and DNAMatch the roles with the molecules.Roles► Master plan - DNA► Goes to the ribosomes in the cytoplasm - RNA► Blueprint – RNA► Remains in the nucleus - DNA
  • Genes and Proteins► Many proteins are_____, which catalyze and regulate chemical reactions.► Enzymes
  • Is the following sentence true or false?Genes are the keys to almost everything that living cells do.false
  • Translation Four Major Steps►A. Messenger RNA is transcribed in the nucleus then enters the cytoplasm and attaches to an ribosome.►B. Transfer RNA translation begins at AUG, the start codon. Each anti-codon of tRNA complements a codon of mRNA and binds a specific amino acid.
  • Translation Four Major Steps cont.► C. The polypeptide “assembly line” as the codons bind amino acids the ribosome joins them together forming long chains of amino acids.► D. Completing the Polypeptide the process continues until one of three stop codons is reached.