1 PROTEIN SYNTHESIS

DNA and Genes 2

Genes & Proteins DNA contains genes, sequences of nucleotide bases These genes code for polypeptides (proteins) Proteins are used to build cells and do much of the work inside cells 3

4 Genes & Proteins, cont. Proteins are made of amino acids linked together by peptide bonds 20 different amino acids exist

5 Amino Acid Structure

6 Genes & Proteins, cont. Amino acid chains are called polypeptides

7 Starting with DNA DNA is found inside the nucleus Proteins are made in the cytoplasm of cells by organelles called ribosomes Ribosomes may be free in the cytosol or attached to the surface of rough ER

8 Starting with DNA, cont. DNA ‘s code must be copied and taken to the cytosolDNA ‘s code must be copied and taken to the cytosol In the cytoplasm, this code must be read so amino acids can be assembled to make proteinsIn the cytoplasm, this code must be read so amino acids can be assembled to make proteins This process is called PROTEIN SYNTHESISThis process is called PROTEIN SYNTHESIS

RNA 9

10 Roles of RNA & DNA DNA is the MASTER PLAN RNA is the BLUEPRINT of the Master Plan

11 Roles of RNA & DNA, cont. RNA has a sugar ribose DNA has a sugar deoxyribose

12 Roles of RNA & DNA, cont. RNA contains the base uracil (U) DNA has thymine (T) RNA molecule is single-stranded DNA is double- stranded DNA

13. 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

14 Messenger RNA Long chain of nucleotides Made in the nucleus Copies DNA & leaves through nuclear pores Carries information for a specific protein

15 Ribosomal RNA (rRNA) rRNA is a single strand 100 to 3000 nucleotides long Globular in shape Made inside the nucleus of a cell Site of protein Synthesis

16 Transfer RNA (tRNA) Clover-leaf shape Single stranded molecule with attachment site at one end for an amino acid Found out in the cytosol

17 Transfer RNA amino acid attachment site UAC

18 The Genetic Code A codon is a set of three RNA bases A codon designates a specific amino acid An amino acid may have more than one codon There are 64 possible codons

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

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

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

Transcription and Translation 22

23 Pathway to Making a Protein DNAmRNA tRNA to ribosomes Protein

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

25 DNA  RNA  Protein Nuclear membrane Transcription RNA Processing Translation DNA Pre-mRNA mRNA Ribosome Protein Eukaryotic Cell

26 Transcription The process of copying the sequence of one strand of DNA mRNA copies the template strand Requires the enzyme RNA Polymerase

27 Template Strand

28 Question: What would be the complementary RNA strand for the following DNA sequence? DNA 5’-GCGTATG-3’

29 Transcription, cont. 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

30 Transcription, cont. Promoters are regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA Specific base sequences act as signals to stop Called the termination signal

31 mRNA Transcript mRNA leaves the nucleus through its pores and goes to the ribosomes

32 Translation Translation is the process of decoding the mRNA into a polypeptide chain Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins

33 Translation, cont. mRNA transcript start codon AUG attaches to the ribosome mRNA transcript

Translation, cont. As ribosome moves, two tRNA with their amino acids move into attachment sites Peptide bonds join the amino acids 34

35 End Product –The Protein! The ribosome knows the protein is complete when it reaches a stop codon Protein - a sequence of amino acid bonded together by peptide bonds Protein is released from ribosome out into cytoplasm

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