12-3 RNA and Protein Synthesis Copyright Pearson Prentice Hall

12–3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins. 1 gene = 1 protein However, the DNA cannot leave the nucleus and proteins are made on ribosomes outside of the nucleus. The solution to this problem is RNA! RNA can copy DNA’s coded information for making proteins and leave the nucleus with the information. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Structure of RNA The Structure of RNA There are four main differences between RNA and DNA: The sugar in RNA is ribose instead of deoxyribose. RNA is single-stranded. DNA is double-stranded. RNA contains uracil in place of thymine. DNA stays in the nucleus, but RNA can leave the nucleus and go into the cytoplasm. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Types of RNA Types of RNA There are three main types of RNA: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Types of RNA The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Types of RNA Ribosome Ribosomal RNA The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Ribosomal RNA is combined with proteins to form ribosomes. Ribosomes are made up of proteins and ribosomal RNA (rRNA). Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Types of RNA Amino acid The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Transfer RNA During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Transcription Transcription Protein synthesis begins in the nucleus with a process called transcription. DNA is copied in the form of a single strand of RNA The process begins at a section of DNA called a promoter. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Transcription RNA RNA polymerase DNA During transcription, RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall An enzyme, RNA Polymerase, acts on the DNA molecule and causes it to unzip. It chemically tells RNA nucleotides to come and base pair with the open DNA molecule according to the base-pairing rules: Adenine-Uracil (A-U) and Cytosine-Guanine (C-G) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall RNA Editing RNA Editing Some DNA within a gene is not needed to produce a protein. Remember, DNA stays in the nucleus, but the edited mRNA leaves the nucleus and goes into the cytoplasm to the ribosome Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Genetic Code The Genetic Code The genetic code is the “language” of mRNA instructions. The code is written using four “letters” (the bases: A, U, C, and G). Adenine, Uracil, Cytosine, Guanine Copyright Pearson Prentice Hall

Protein Synthesis DNA molecule DNA strand (template) 3′ 5′ TRANSCRIPTION mRNA 5′ 3′ Codon TRANSLATION Protein Amino acid

Copyright Pearson Prentice Hall Translation Translation Translation is the decoding of a mRNA message into an amino acid (protein). Translation takes place on ribosomes. During translation, the cell uses information from messenger RNA to produce proteins. Nucleus mRNA Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Translation The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA by matching tRNA anticodons to mRNA codons according to base pairing rules: A-U C-G Lysine Phenylalanine tRNA Methionine Ribosome During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRNA Start codon Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Translation As the amino acids are brought close together, they are joined by bonds to make a protein. Protein Synthesis Lysine tRNA During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRNA Translation direction Ribosome Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Translation The process continues until the ribosome reaches a stop codon. Polypeptide Ribosome tRNA During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRNA Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid. A codon is a group of three nucleotides on messenger RNA that specify a particular amino acid. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Genetic Code Codons are read from the center out For example: The codon “AAC” codes for the amino acid “Asparagine”. The genetic code shows the amino acid to which each of the 64 possible codons corresponds. To decode a codon, start at the middle of the circle and move outward. GCU codes for Alanine. What other codons will produce Alanine? Copyright Pearson Prentice Hall

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Amino acids within a polypeptide Genes and Proteins Codon Codon Codon DNA mRNA Protein Single strand of DNA Codon Codon Codon mRNA This diagram illustrates how information for specifying the traits of an organism is carried in DNA. The sequence of bases in DNA is used as a template for mRNA. The codons of mRNA specify the sequence of amino acids in a protein, and proteins play a key role in producing an organism’s traits. Alanine Arginine Leucine Amino acids within a polypeptide Copyright Pearson Prentice Hall

Protein Synthesis DNA molecule DNA strand (template) 3′ 5′ TRANSCRIPTION mRNA 5′ 3′ Codon TRANSLATION Protein Amino acid

Copyright Pearson Prentice Hall 12–3 Write the letters that correspond to your answers on the quiz below in you summary section. You do not need to write out the question or answer ifself. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 12–3 The role of a master plan in a building is similar to the role of which molecule? messenger RNA DNA transfer RNA ribosomal RNA Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 12–3 A base that is present in RNA but NOT in DNA is thymine. uracil. cytosine. adenine. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 12–3 The nucleic acid responsible for bringing individual amino acids to the ribosome is transfer RNA. DNA. messenger RNA. ribosomal RNA. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 12–3 A codon typically carries sufficient information to specify a(an) single base pair in RNA. single amino acid. entire protein. single base pair in DNA. Copyright Pearson Prentice Hall