PROTEIN SYNTHESIS copyright cmassengale 1 DNA and Genes

PROTEIN SYNTHESIS copyright cmassengale 1

DNA and Genes copyright cmassengale 2

DNA • 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 copyright cmassengale 3

Review • What are the 3 parts of DNA? – Deoxyribose sugar, phosphate, and 4 nitrogen bases • What are the 4 nitrogen bases? – Adenine (A), Guanine (G), Thymine (T), Cytosine (C) • If the sequence of DNA is ATTCGG, what would be the complementary strand? – TAAGCC

Genes & Proteins § Proteins are made of amino acids linked together by peptide bonds § Amino acid chains are called polypeptides copyright cmassengale 5

Amino acids § 20 different amino acids exist copyright cmassengale 6

Amino Acid Structure copyright cmassengale 7

DNA Begins the Process • DNA is found inside the nucleus • Proteins, however, 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 copyright cmassengale 8

Starting with DNA • DNA ‘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 polypeptides (proteins) • This process is called PROTEIN SYNTHESIS copyright cmassengale 9

RNA copyright cmassengale 10

Roles of RNA and DNA • DNA is the MASTER PLAN • RNA is the BLUEPRINT of the Master Plan copyright cmassengale 11

RNA Differs from DNA • RNA has a sugar ribose DNA has a sugar deoxyribose copyright cmassengale 12

Other Differences • • RNA contains the base uracil (U) DNA has thymine (T) RNA molecule is single-stranded DNA is doublestranded copyright cmassengale DNA 13

RNA (ribonucleic acid) – So if you had the following DNA strand, what would the RNA strand be? – DNA Strand: T G C A T C A G A – RNA Strand: A C G U A G U C U

Structure of RNA copyright cmassengale 15

. Three Types of RNA • Messenger RNA (m. RNA) copies DNA’s code & carries the genetic information to the ribosomes • Ribosomal RNA (r. RNA), along with protein, makes up the ribosomes • Transfer RNA (t. RNA) transfers amino acids to the ribosomes where proteins are synthesized copyright cmassengale 16

Messenger RNA • Long Straight chain of Nucleotides • Made in the Nucleus • Copies DNA & leaves through nuclear pores copyright cmassengale 17

The Genetic Code • Sequence of 3 bases called codon • 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 18 copyright cmassengale

The Genetic Code copyright cmassengale 19

Name the Amino Acids • • • GGG? UCA? CAU? GCA? AAA? copyright cmassengale 20

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

Transfer RNA (t. RNA) • 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 copyright cmassengale 22

Transfer RNA amino acid attachment site U A C anticodon copyright cmassengale 23

Codons and Anticodons • The 3 bases of an anticodon are complementary to the 3 bases of a codon • Example: Codon ACU Anticodon UGA copyright cmassengale UGA ACU 24

Transcription and Translation copyright cmassengale 25

Pathway to Making a Protein DNA m. RNA t. RNA (ribosomes) Protein copyright cmassengale 26

Protein Synthesis § The production or synthesis of polypeptide chains (proteins) § Two phases: Transcription & Translation § m. RNA must be processed before it leaves the nucleus of eukaryotic cells copyright cmassengale 27

DNA RNA Protein Nuclear membrane DNA Transcription Eukaryotic Cell Pre-m. RNA Processing m. RNA Ribosome Translation Protein copyright cmassengale 28

Transcription • Happens in the nucleus • The process of copying the sequence of one strand of DNA, the template strand in the nucleus • m. RNA copies the template strand copyright cmassengale 29

Template Strand copyright cmassengale 30

Question: § What would be the complementary RNA strand for the following DNA sequence? DNA 5’-GCGTATG-3’ copyright cmassengale 31

Answer: • DNA 5’-GCGTATG-3’ • RNA 3’-CGCAUAC-5’ copyright cmassengale 32

RNA Polymerase copyright cmassengale 33

m. RNA Transcript • m. RNA leaves the nucleus through its pores and goes to the ribosomes copyright cmassengale 34

Translation • Happens in cytoplasm • t. RNA decodes m. RNA in order to make the correct protein • Ribosomes read m. RNA three bases or 1 codon at a time and construct the proteins copyright cmassengale 35

Transcription Translation copyright cmassengale 36

Step 1 - Initiation • m. RNA transcript start codon AUG attaches to the small ribosomal subunit • Small subunit attaches to large ribosomal subunit m. RNA transcript copyright cmassengale 37

Ribosomes Large subunit P Site A Site m. RNA Small subunit A U G C U A C U U C G copyright cmassengale 38

Step 2 - Elongation • As ribosome moves, two t. RNA with their amino acids move into site A and P of the ribosome • Peptide bonds join the amino acids copyright cmassengale 39

Initiation aa 2 aa 1 2 -t. RNA 1 -t. RNA anticodon hydrogen bonds U A C A U G codon G A U C U A C U U C G A copyright cmassengale m. RNA 40

Elongation peptide bond aa 1 aa 3 aa 2 3 -t. RNA 1 -t. RNA anticodon hydrogen bonds U A C A U G codon 2 -t. RNA G A U C U A C U U C G A copyright cmassengale m. RNA 41

aa 1 peptide bond aa 3 aa 2 1 -t. RNA 3 -t. RNA U A C (leaves) 2 -t. RNA A U G G A A G A U C U A C U U C G A m. RNA copyright cmassengale Ribosomes move over one codon 42

aa 1 peptide bonds aa 2 aa 4 aa 3 4 -t. RNA 2 -t. RNA A U G 3 -t. RNA G C U G A A C U U C G A A C U m. RNA copyright cmassengale 43

aa 1 peptide bonds aa 4 aa 2 aa 3 2 -t. RNA 4 -t. RNA G A U (leaves) 3 -t. RNA A U G G C U G A A C U U C G A A C U m. RNA copyright cmassengale Ribosomes move over one codon 44

aa 1 peptide bonds aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA 4 -t. RNA G A A G C U A C U U C G A A C U m. RNA copyright cmassengale 45

peptide bonds aa 1 aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA G A A 4 -t. RNA G C U A C U U C G A A C U m. RNA copyright cmassengale Ribosomes move over one codon 46

aa 4 aa 5 Termination aa 199 aa 3 primary structure aa 2 of a protein aa 200 aa 1 200 -t. RNA A C U terminator or stop codon C A U G U U U A G m. RNA copyright cmassengale 47

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 aa 2 aa 1 aa 3 aa 4 aa 5 aa 199 copyright cmassengale aa 200 48

Messenger RNA (m. RNA) start codon m. RNA A U G G G C U C C A U C G G C A U A A codon 1 protein methionine codon 2 codon 3 glycine serine codon 4 isoleucine codon 5 codon 6 glycine alanine codon 7 stop codon Primary structure of a protein aa 1 aa 2 aa 3 aa 4 cmassengale peptidecopyright bonds aa 5 aa 6 49

DNA RNA Protein DNA code Start 1 st Codon 2 nd Codon 3 rd Codon TAC AGT CGG GCT m-RNA code AUG UCA GCC CGA t- RNA code UAC AGU CGG GCU Amino Acid Methionin Serine e Alanine Arginine