DNA is the MASTER PLAN. RNA is the BLUEPRINT of the Master Plan

Transcription

1 Sec RNA and Protein Synthesis Roles of DNA and RNA DNA is the MASTER PLAN RNA is the BLUEPRINT of the Master Plan 1

2 RNA uses the information from DNA to make proteins Differs from DNA: 1. Ribose is the five-carbon sugar 2. Nitrogen base uracil rather than thymine 3. Only one strand of nucleotide Think of RNA as a disposable copy of a segment of DNA

3 One Strand of RNA The backbone of the molecule is alternating phosphates and ribose sugar The teeth are nitrogenous bases. phosphate ribose bases

4 . Three Types of RNA Messenger RNA (mrna) copies DNA s code & carries the genetic information to the ribosomes Ribosomal RNA (rrna), along with protein, makes up the ribosomes Transfer RNA (trna) transfers amino acids to the ribosomes where proteins are synthesized 4

5 Messenger RNA Long Straight chain of Nucleotides Made in the Nucleus Copies DNA & leaves through nuclear pores Contains the Nitrogen Bases A, G, C, U (no T) 5

6 Messenger RNA (mrna) Carries the information for a specific protein Made up of 500 to 1000 nucleotides long Sequence of 3 bases called codon AUG methionine or start codon UAA, UAG, or UGA stop codons 6

7 Ribosomal RNA (rrna) rrna is a single strand 100 to 3000 nucleotides long Globular in shape Made inside the nucleus of a cell Associates with proteins to form ribosomes Site of protein Synthesis 7

8 Transfer RNA (trna) Clover-leaf shape Single stranded molecule with attachment site at one end for an amino acid Opposite end has three nucleotide bases called the anticodon amino acid attachment site U A C anticodon 8

9 Transcription The process of copying the sequence of one strand of DNA, the template strand mrna copies the template strand Requires the enzyme RNA Polymerase 9

10 Transcription During transcription, RNA polymerase binds to DNA and separates the DNA strands RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA 10

11 Bonds form between the bases of a DNA strand and complementary bases of floating RNA nucleotides Enzyme establishes sugar-tophosphate bonds between RNA nucleotides When the termination signal on DNA is reached, the new RNA is released

12 The enzyme will bind only to regions of DNA known as promoters, which have a specific base sequence. Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA

13 All 3 types of RNA are copied in this manner and move from the nucleus into the cytoplasm, where they are involved in the synthesis of protein. RNA has a base sequence complimentary to DNA

14 mrna Transcript mrna leaves the nucleus through its pores and goes to the ribosomes 14

15 The Genetic Code A codon designates an amino acid An amino acid may have more than one codon There are 20 amino acids, but 64 possible codons Some codons tell the ribosome to stop translating 15

16 Use the code by reading from the center to the outside Example: AUG codes for Methionine The Genetic Code 16

17 Name the Amino Acids GGG? UCA? CAU? GCA? AAA? 17

18 Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G 18

19 PROTEIN SYNTHESIS 19

20 Protein Synthesis The production (synthesis) of polypeptide chains (proteins) Two phases: Transcription & Translation mrna must be processed before it leaves the nucleus of eukaryotic cells 20

21 Pathway to Making a Protein DNA mrna trna (ribosomes) Protein 21

22 Making a Protein 22

23 Genes & Proteins Proteins are made of amino acids linked together by peptide bonds 20 different amino acids exist Amino acids chains are called polypeptides Segment of DNA that codes for the amino acid sequence in a protein are called genes 23

24 Two Parts of Protein Synthesis Transcription makes an RNA molecule complementary to a portion of DNA Translation occurs when the sequence of bases of mrna DIRECTS the sequence of amino acids in a polypeptide 24

25 Genetic Code DNA contains a triplet code Every three bases on DNA stands for ONE amino acid Each three-letter unit on mrna is called a codon Most amino acids have more than one codon! There are 20 amino acids with a possible 64 different triplets The code is nearly universal among living organisms 25

26 26

27 Transfer RNA (trna) amino acid attachment site methionine amino acid U A C anticodon 27

28 Ribosomes Large subunit P Site A Site Small subunit A U G mrna C U A C U U C G 28

29 Translation Synthesis of proteins in the cytoplasm Involves the following: 1. mrna (codons) 2. trna (anticodons) 3. ribosomes 4. amino acids 29

30 Translation Three steps: 1. initiation: start codon (AUG) 2. elongation: amino acids linked 3. termination: stop codon (UAG, UAA, or UGA). Let s Make a Protein! 30

31 mrna Codons Join the Ribosome Large subunit P Site A Site Small subunit A U G mrna C U A C U U C G 31

32 Initiation aa1 aa2 anticodon hydrogen bonds 1-tRNA U A C A U G codon 2-tRNA G A U C U A C U U C G A mrna 32

33 Elongation peptide bond aa1 aa2 aa3 anticodon hydrogen bonds 1-tRNA U A C A U G codon 2-tRNA 3-tRNA G A A G A U C U A C U U C G mrna 33 A

34 aa1 aa2 peptide bond aa3 1-tRNA U A C (leaves) 2-tRNA 3-tRNA G A A G A U A U G C U A C U U C G A Ribosomes move over one codon mrna 34

35 aa1 peptide bonds aa4 aa2 aa3 4-tRNA 2-tRNA 3-tRNA G C U A U G G A U G A A C U A C U U C G A A C U mrna 35

36 aa1 peptide bonds aa2 aa3 aa4 G 2-tRNA A U (leaves) 3-tRNA 4-tRNA G C U G A A A U G C U A C U U C G A A C U Ribosomes move over one codon mrna 36

37 aa1 aa2 peptide bonds aa3 aa4 aa5 5-tRNA U G A 3-tRNA 4-tRNA G A A G C U G C U A C U U C G A A C U mrna 37

38 aa1 aa2 peptide bonds aa3 aa4 aa5 5-tRNA 3-tRNA G A A 4-tRNA G C U G C U A C U U C G A A C U Ribosomes move over one codon U G A mrna 38

39 aa4 aa5 aa199 Termination aa3 aa2 primary structure of a protein aa200 aa1 200-tRNA terminator or stop codon A C U C A U G U U U A G mrna 39

40 End Product The Protein! The end products of protein synthesis is a primary structure of a protein A sequence of amino acid bonded together by peptide bonds aa2 aa3 aa4 aa5 aa199 aa1 aa200 40

41 Messenger RNA (mrna) mrna start codon A U G G G C U C C A U C G G C G C A U A A codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 protein methionine glycine serine isoleucine glycine alanine stop codon Primary structure of a protein aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds 41