Hemophilia- Caused by a defect in a single gene cannot produce all the proteins necessary for blood clotting Depend on expensive injections of clotting proteins to prevent uncontrolled bleeding

nuclear pore chromatin (DNA) nucleus nucleolus nuclear envelope flagellum intermediate filaments cytoplasm plasma membrane rough endoplasmic reticulum ribosome lysosome Figure: 04-02 Title: A generalized animal cell. Caption: microtubules smooth endoplasmic reticulum Golgi complex free ribosome vesicle mitochondrion vesicle

Protein Synthesis Gene Expression

The relationship of Chromosomes, DNA, Genes & Proteins The relationship of Chromosomes, Genes, DNA & Proteins Franklin's Legacy | PBS DNA to Protein

Genes and Proteins Genes provide information to make proteins Genetic information for protein synthesis is carried by RNA (ribonucleic acid) intermediates

The genetic code and codons A sequence of nucleotide bases in DNA is translated into a sequence of amino acids in a protein.

Protein Synthesis Two-step process Transcription and Translation Transcription—nucleotide message sent from nucleus to cytoplasm DNA nucleotide sequence "copied" (using complementary base pairing) as a "messenger" nucleotide sequence of RNA (mRNA)

Translation produces a protein molecule with an amino acid gene 3 gene 1 DNA gene 2 (nucleus) (cytoplasm) Transcription of gene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands. (a) TRANSCRIPTION messenger RNA Figure: 09-01 Title: Genetic information flows from DNA to RNA to protein. Caption: After being transcribed, the mRNA molecule moves from the nucleus to the cytoplasm, where it is translated. protein (b) TRANSLATION Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.

Protein Synthesis 1. Transcription… b. RNA polymerase catalyzes synthesis of mRNA; similar to DNA replication and DNA polymerase Promoter sequence binds RNA polymerase Termination signal is a sequence of nucleotides at end of genes that tell RNA polymerase to stop transcription

Translation produces a protein molecule with an amino acid gene 3 gene 1 DNA gene 2 (nucleus) (cytoplasm) Transcription of gene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands. (a) TRANSCRIPTION messenger RNA Figure: 09-01 Title: Genetic information flows from DNA to RNA to protein. Caption: After being transcribed, the mRNA molecule moves from the nucleus to the cytoplasm, where it is translated. protein (b) TRANSLATION Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.

Protein Synthesis 1. Transcription… c. The entire DNA molecule in a chromosome is not transcribed, only a specific gene or family of genes is transcribed

chromosome DNA gene 1 gene 2 gene 3 (a) initiation template strand Figure: 09-03a Title: Initiation and elongation are the first two steps of transcription. Caption: (a) Initiation: The enzyme RNA polymerase binds to the promoter region of DNA near the beginning of a gene, forcing the DNA double helix to separate in front of it. template strand RNA polymerase

(b) elongation RNA Figure: 09-03b Title: Initiation and elongation are the first two steps of transcription. Caption: (b) Elongation: RNA polymerase travels along the DNA template strand, catalyzing the formation of a complementary RNA molecule from free RNA nucleotides. As RNA polymerase moves along, the already transcribed portion of the DNA double helix begins to rewind. RNA

direction of transcription beginning of gene growing RNA RNA molecules Figure: 09-04b Title: RNA transcription in action. Caption: In each treelike structure, the central “trunk” is DNA and the “branches” are RNA molecules. RNA polymerase molecules are traveling along the DNA, synthesizing RNA as they go. The beginning of the gene is on the left, and the short RNA molecules on the left have just begun to be synthesized; the long RNA molecules on the right are almost finished. growing RNA molecules RNA polymerase DNA

Figure: 09-04a Title: RNA transcription in action. Caption: The images in this electron micrograph show RNA transcription. In each treelike structure, the central “trunk” is DNA and the “branches” are RNA molecules. RNA polymerase molecules are traveling along the DNA, synthesizing RNA as they go. The beginning of the gene is on the left, and the short RNA molecules on the left have just begun to be synthesized; the long RNA molecules on the right are almost finished.

(a) RNA polymerase termination signal Figure: 09-05a Title: Termination is the third step of transcription. Caption: Elongation of the RNA molecule continues until (a) RNA polymerase encounters, at the end of gene, a termination signal.

Initiation, Elongation and Termination (b) Figure: 09-05b Title: Termination is the third step of transcription. Caption: (b) RNA polymerase detaches from the DNA and releases the RNA molecule, allowing the DNA double helix to completely rewind. RNA Initiation, Elongation and Termination

Translation produces a protein molecule with an amino acid gene 3 gene 1 DNA gene 2 (nucleus) (cytoplasm) Transcription of gene 1 produces an mRNA with a nucleotide sequence complementary to one of the DNA strands. (a) TRANSCRIPTION messenger RNA Figure: 09-01 Title: Genetic information flows from DNA to RNA to protein. Caption: After being transcribed, the mRNA molecule moves from the nucleus to the cytoplasm, where it is translated. protein (b) TRANSLATION Translation produces a protein molecule with an amino acid sequence determined by the nucleotide sequence in the mRNA.

Protein Synthesis 2. Translation—nucleotide sequence of mRNA used to synthesize a sequence of amino acids (polypeptide or protein) a. Occurs on the endoplasmic reticulum using ribosomes

rough endoplasmic reticulum smooth endoplasmic reticulum ribosomes 0.5 micrometers smooth endoplasmic reticulum Figure: 04-07 Title: Endoplasmic reticulum. Caption: There are two types of endoplasmic reticulum: rough ER, coated with ribosomes, and smooth ER, without ribosomes. Although in electron micrographs the ER looks like a series of tubes and sacs, it is actually a maze of folded sheets and interlocking channels. 0.5 micrometers vesicles

Protein Synthesis 2. Translation… b. mRNA codons are used to specify amino acids c. Ribosomes "read" mRNA codons to synthesize a specific amino acid sequence

A Codon = three nucleotide bases (a) messenger RNA Figure: 09-02a Title: Cells synthesize three major types of RNA. Caption: (a) mRNA is a sequence of nucleotides that encodes a protein. A Codon = three nucleotide bases

(b) ribosome (contains ribosomal RNA) catalytic site large subunit tRNA/amino acid binding sites Figure: 09-02b Title: Cells synthesize three major types of RNA. Caption: (b) rRNA is a major component of the two subunits that join together to form a ribosome. small subunit

Protein Synthesis 2. Translation… d. Each of the 20 amino acids has a specific "carrier" transfer RNA (tRNA) that brings the amino acid to the ribosome e. Complementary base pairing between the mRNA and tRNAs determines the amino acid sequence

(c) transfer RNA attached amino acid anticodon Figure: 09-02c Title: Cells synthesize three major types of RNA. Caption: (c) One side of tRNA contains an anticodon that is complementary to an mRNA codon; the opposite side binds an amino acid. anticodon

(a) messenger RNA (b) ribosome (contains ribosomal RNA) catalytic site large subunit tRNA/amino acid binding sites small subunit Figure: 09-02a-c Title: Cells synthesize three major types of RNA. Caption: RNA consists of a single strand of nucleotides whose sequence is complementary to that of the DNA from which it was transcribed. (a) mRNA is a sequence of nucleotides that encodes a protein. (b) rRNA is a major component of the two subunits that join together to form a ribosome. (c) One side of tRNA contains an anticodon that is complementary to an mRNA codon; the opposite side binds an amino acid. (c) transfer RNA attached amino acid anticodon

Protein Synthesis 2. Translation… f. Ribosomes need to recognize the beginning and end of the mRNA message 1) Initiation (start) codon: AUG (methionine) 2) Stop codons: UAA, UAG, UGA

A tRNA with an attached methionine amino acid binds to small initiation complex small ribosomal subunit Figure: 09-06a Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (a) A tRNA with an attached methionine amino acid binds to small ribosomal subunit, forming an initiation complex.

The initiation complex binds to the end of an mRNA and tRNA mRNA Figure: 09-06b Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (b) The initiation complex binds to the end of an mRNA and travels along the mRNA until it encounters an AUG codon. The anticodon of the tRNA pairs with the AUG codon.

The large ribosomal subunit binds to the small subunit, with the second binding site catalytic site large ribosomal subunit first binding site Figure: 09-06c Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (c) The large ribosomal subunit binds to the small subunit, with the mRNA between the two subunits. The methionine tRNA is in the first binding site on the large subunit.

A second tRNA enters the second binding site. Its catalyic site Figure: 09-06d Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (d) A second tRNA enters the second binding site. Its anticodon pairs with the codon in the mRNA. The tRNA carries an attached amino acid.

The catalytic site catalyzes the formation peptide bond Figure: 09-06e Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (e) The catalytic site catalyzes the formation of a peptide bond that links the two amino acids. Both amino acids are now attached to the tRNA in the second binding position.

ribosome moves one codon to right catalytic site tRNA detaches Figure: 09-06f Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: ribosome moves one codon to right (f) The “empty” tRNA is released and the ribosome moves one codon to the right. The tRNA with the two amino acids is now in the first tRNA binding site. The second tRNA binding site is empty.

Another tRNA, with an anticodon complementary to the next mRNA catalytic site Figure: 09-06g Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (g) Another tRNA, with an anticodon complementary to the next mRNA codon, enters the second binding site. This tRNA carries the next amino acid to be added to the chain.

The catalytic site forms a peptide bond that attaches the new amino Figure: 09-06h Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (h) The catalytic site forms a peptide bond that attaches the new amino acid at the end of the chain. The chain of three amino acids is now attached to the tRNA in the second binding site. The empty tRNA in the first site will be released and the ribosome will move one codon to the right.

Binding of tRNAs and formation of peptide bonds between amino acids completed peptide stop codon Figure: 09-06i Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: (i) Binding of tRNAs and formation of peptide bonds between amino acids continues until the ribosomes reaches a stop codon. No tRNA binds to stop codons. Instead, protein “release factors” signal the ribosome to release the newly made protein. The mRNA is also released, and the subunits separate.

tRNA detaches catalytic site catalytic site catalytic site second binding site large ribosomal subunit amino acid catalytic site methionine tRNA tRNA initiation complex first binding site small ribosomal subunit mRNA (a) (b) (c) tRNA detaches catalytic site catalytic site peptide bond ribosome moves one codon to the right (d) (e) (f) Figure: 09-06A-I Title: Translation: the base sequence of an mRNA is translated into the amino acid sequence of a protein. Caption: catalytic site completed peptide stop condon (g) (h) (i)

gene (a) gene in DNA (template strand) codon (b) mRNA (codons) anticodon Figure: 09-07a-d Title: Complementary base pairing is critical at each step in decoding genetic information Caption: (a) DNA contains two strands. One of them, the template strand, is used to synthesize an RNA molecule. (b) Bases in the template strand are transcribed into complementary mRNA codons. (c) Unless it is a stop codon, each mRNA codon forms base pairs with the anticodon of a tRNA molecule that carries a specific amino acid. (d) The amino acids are linked together, forming a protein. (c) tRNA (anticodons) amino acids (d) protein (amino acids)

Review Protein Synthesis Two Major Steps of Protein Synthesis Transcription & Translation Initiation, Elongation and Termination