Biology. Biology. Slide 1 of 39. End Show. Copyright Pearson Prentice Hall

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1 Biology Biology 1 of 39

2 12-3 RNA and Protein Synthesis 2 of 39

3 Essential Question What is transcription and translation and how do they take place? 3 of 39

4 12 3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins. 4 of 39

5 The Structure of RNA The Structure of RNA RNA consists of a long chain of nucleotides. Each nucleotide is made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. 5 of 39

6 The Structure of RNA 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. 6 of 39

7 Types of RNA What are the three main types of RNA? 7 of 39

8 Types of RNA Types of RNA There are three main types of RNA: messenger RNA ribosomal RNA transfer RNA 8 of 39

9 Types of RNA Messenger RNA (mrna) carries copies of instructions for assembling amino acids into proteins. 9 of 39

10 Types of RNA Ribosome Ribosomal RNA Ribosomes are made up of proteins and ribosomal RNA (rrna). 10 of 39

11 Types of RNA Amino acid Transfer RNA During protein construction, transfer RNA (trna) transfers each amino acid to the ribosome. 11 of 39

12 Transcription What is transcription? 12 of 39

13 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. 13 of 39

14 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. 14 of 39

15 Transcription RNA polymerase binds only to regions of DNA known as promoters. Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA. 15 of 39

16 Transcription RNA RNA polymerase DNA 16 of 39

17 RNA Editing RNA Editing The DNA of eukaryotic genes contains sequences of nucleotides, called introns, that are not involved in coding for proteins. The DNA sequences that code for proteins are called exons. When RNA molecules are formed, introns and exons are copied from DNA. 17 of 39

18 RNA Editing The introns are cut out of RNA molecules. Exon Intron DNA The exons are the spliced together to form mrna. Pre-mRNA mrna Cap Tail 18 of 39

19 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). 19 of 39

20 The Genetic Code A codon consists of three consecutive nucleotides on mrna that specify a particular amino acid. 20 of 39

21 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. 21 of 39

22 The Genetic Code 22 of 39

23 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. 23 of 39

24 Translation What is translation? 24 of 39

25 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. 25 of 39

26 Translation Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome. Nucleus mrna 26 of 39

27 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. 27 of 39

28 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. 28 of 39

29 Translation The ribosome binds new trna molecules and amino acids as it moves along the mrna. Methionine Phenylalanine trna Lysine Ribosome mrna Start codon 29 of 39

30 Translation Protein Synthesis Lysine trna mrna Ribosome Translation direction 30 of 39

31 Translation The process continues until the ribosome reaches a stop codon. Polypeptide trna Ribosome mrna 31 of 39

32 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. 32 of 39

33 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. 33 of 39

34 Codon Genes and Proteins 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 Alanine Arginine Leucine Amino acids within a polypeptide 34 of 39

35 12 3 Continue to: - or - Click to Launch: 35 of 39

36 12 3 The role of a master plan in a building is similar to the role of which molecule? a. messenger RNA b. DNA c. transfer RNA d. ribosomal RNA 36 of 39

37 12 3 A base that is present in RNA but NOT in DNA is a. thymine. b. uracil. c. cytosine. d. adenine. 37 of 39

38 12 3 The nucleic acid responsible for bringing individual amino acids to the ribosome is a. transfer RNA. b. DNA. c. messenger RNA. d. ribosomal RNA. 38 of 39

39 12 3 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the a. intron. b. exon. c. promoter. d. codon. 39 of 39

40 12 3 A codon typically carries sufficient information to specify a(an) a. single base pair in RNA. b. single amino acid. c. entire protein. d. single base pair in DNA. 40 of 39