Copyright Pearson Prentice Hall Biology Biology Copyright Pearson Prentice Hall
12-3 RNA and Protein Synthesis 4.3—Recognize the interactions between DNA and RNA during protein synthesis 12-3 RNA and Protein Synthesis Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Write this down There are three main differences between RNA and DNA: The sugar in RNA is ribose instead of deoxyribose. RNA is generally single-stranded. RNA contains uracil in place of thymine. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Write this down Protein synthesis—The process used by the body to make proteins. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Types of RNA Types of RNA There are three main types of RNA: messenger RNA ribosomal RNA transfer RNA 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 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 What is transcription? Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Transcription Transcription RNA molecules are produced by copying part of a nucleotide sequence of DNA into a complementary sequence in RNA. This process is called transcription. Transcription requires the enzyme RNA polymerase. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Transcription During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. Copyright Pearson Prentice Hall
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 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 Each codon specifies a particular amino acid that is to be placed on the polypeptide chain. Some amino acids can be specified by more than one codon. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall The Genetic Code 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. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall The Genetic Code There is one codon AUG that can either specify the amino acid methionine or serve as a “start” codon for protein synthesis. There are three “stop” codons that do not code for any amino acid. These “stop” codons signify the end of a polypeptide. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Write this down Protein synthesis—The process used by the body to make proteins. 1. Transcription—in the nucleus—mRNA copies DNA and leaves nucleus Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Translation What is translation? Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Translation Translation Translation is the decoding of an mRNA message into a polypeptide chain (protein). Translation takes place on ribosomes. During translation, the cell uses information from messenger RNA to produce proteins. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Translation Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome. Nucleus 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 Translation Translation begins when an mRNA molecule attaches to a ribosome. As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA. In the ribosome, the amino acid is transferred to the growing polypeptide chain. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Translation Each tRNA molecule carries only one kind of amino acid. In addition to an amino acid, each tRNA molecule has three unpaired bases. These bases, called the anticodon, are complementary to one mRNA codon. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Translation The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA. 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 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 Write this down Protein synthesis—The process used by the body to make proteins. Transcription—in the nucleus—mRNA copies DNA and leaves nucleus Translation—in the cytoplasm—mRNA attaches to ribosome. Starting with the “start” codon, three bases (codons) matches with a tRNA (anticodon). Each tRNA carries only one kind of amino acid. The amino acids create a chain until the “stop” codon is reached. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall The Roles of RNA and DNA The Roles of RNA and DNA The cell uses the DNA “master plan” to prepare RNA “blueprints.” The DNA stays in the nucleus. The RNA molecules go to the protein building sites in the cytoplasm—the ribosomes. Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall Genes and Proteins Genes and Proteins Genes contain instructions for assembling proteins. Many proteins are enzymes, which catalyze and regulate chemical reactions. Proteins are each specifically designed to build or operate a component of a living cell. Copyright Pearson Prentice Hall
Amino acids within a polypeptide Genes and Proteins Codon Codon Codon 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. 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