Matakuliah Genetika (BIO612206) Jurusan Biologi FMIPA Universitas Lampung Priyambodo, M.Sc. staff.unila.ac.id/priyambodo
Prokariotik Eukariotik staff.unila.ac.id/priyambodo
Regulasi ekspresi gen pada prokariotik lebih sederhana daripada pada eukariotik Tidak ada intron Transkripsi dan translasi terjadi dalam 1 kompartemen yang sama Pada organisme prokariotik, promoter bersifat polisistronik Satu promoter menjadi regulator bagi beberapa gen disebut juga operon staff.unila.ac.id/priyambodo
trp operon Promoter Operator Genes of operon trpd trpe trpc trpb trpa RNA polymerase mrna 5 Start codon Stop codon E D C B A Polypeptides that make up enzymes for tryptophan synthesis staff.unila.ac.id/priyambodo
Bagian gen yang terletak di sebelah hilir (down stream) dari gen struktural. Fungsi : memberikan sinyal pada enzim RNA Polimerase agar menghentikan proses transkripsi Umumnya berupa struktur hairpin dan lengkungan (loop) staff.unila.ac.id/priyambodo
Terjadi simultan dengan transkripsi staff.unila.ac.id/priyambodo
TRANSCRIPTION 1 RNA is transcribed from a DNA template. 3 DNA 5 RNA transcript RNA PROCESSING 2 In eukaryotes, the RNA transcript (premrna) is spliced and modified to produce mrna, which moves from the nucleus to the cytoplasm. Exon NUCLEUS FORMATION OF INITIATION COMPLEX CYTOPLASM After leaving the nucleus, mrna attaches to the ribosome. Ribosomal subunits RNA polymerase RNA transcript (pre-mrna) Intron Growing polypeptide Amino acid trna Aminoacyl-tRNA synthetase AMINO ACID ACTIVATION 3 4 Each amino acid attaches to its proper trna with the help of a specific enzyme and ATP. mrna Activated amino acid staff.unila.ac.id/priyambodo 5 E A A A A U G G U U U A U G Ribosome Codon TRANSLATION 5 A succession of trnas add their amino acids to the polypeptide chain Anticodon as the mrna is moved through the ribosome one codon at a time. (When completed, the polypeptide is released from the ribosome.)
Signal DNA Cap RNA Gene NUCLEUS Chromatin Chromatin modification: DNA unpacking involving histone acetylation and DNA demethlation Exon Gene available for transcription Transcription Primary transcript Intron RNA processing Tail mrna in nucleus Transport to cytoplasm Degradation of mrna CYTOPLASM mrna in cytoplasm Translation Polypetide Cleavage Chemical modification Transport to cellular destination Active protein Degradation of protein Degraded protein staff.unila.ac.id/priyambodo
Enhancer (distal control elements) Proximal control elements Poly-A signal sequence Termination region DNA Upstream Chromatin changes Transcription RNA processing Promoter Primary RNA transcript 5 (pre-mrna) Intron RNA Exon Intron Exon Intron Exon Intron Exon Transcription Intron Exon Exon RNA processing: Cap and tail added; introns excised and exons spliced together Poly-A signal Downstream Cleared 3 end of primary transport mrna degradation Translation Coding segment Protein processing and degradation mrna G P P P 5 Cap 5 UTR (untranslated region) Start codon Stop codon 3 UTR Poly-A (untranslated tail region) staff.unila.ac.id/priyambodo
Distal control element Activators Promoter Gene Enhancer 1 Activator proteins bind to distal control elements grouped as an enhancer in the DNA. This enhancer has three binding sites. 2 A DNA-bending protein brings the bound activators closer to the promoter. Other transcription factors, mediator proteins, and RNA polymerase are nearby. DNA-bending protein TATA box General transcription factors Group of Mediator proteins RNA Polymerase II 3 The activators bind to certain general transcription factors and mediator proteins, helping them form an active transcription initiation complex on the promoter. Chromatin changes Transcription RNA processing mrna Translation degradation Protein processing and degradation Transcription Initiation complex RNA Polymerase II RNA synthesis staff.unila.ac.id/priyambodo
Mekanisme post-transkripsi A modified guanine nucleotide added to the 5 end 50 to 250 adenine nucleotides added to the 3 end TRANSCRIPTION DNA RNA PROCESSING Pre-mRNA mrna Ribosome TRANSLATION Polypeptide 5 G P P P 5 Cap 5 UTR Protein-coding segment Start codon Stop codon Polyadenylation signal AAUAAA 3 UTR 3 AAA AAA Poly-A tail TRANSCRIPTION RNA PROCESSING mrna TRANSLATION DNA Pre-mRNA Ribosome Pre-mRNA 5 5 Cap 1 Exon Intron 30 31 Exon Coding segment Intron Exon 3 Poly-A tail 104 105 146 Introns cut out and exons spliced together Polypeptide mrna 5 Cap Poly-A tail 1 3 UTR 146 3 UTR staff.unila.ac.id/priyambodo
5 RNA transcript (pre-mrna) Exon 1 Intron Exon 2 1 Protein snrna Other proteins snrnps Spliceosome 2 5 3 Spliceosome components 5 mrna Exon 1 Exon 2 Cut-out intron staff.unila.ac.id/priyambodo
Growing Protein Chain Free amino acids free trna AA:tRNA Anti-codon mrna Ribosome Codon for specific AA Codon staff.unila.ac.id/priyambodo
TRANSCRIPTION TRANSLATION DNA mrna Ribosome Polypeptide Polypeptide Amino acids trna with amino acid Ribosome attached Gly trna A A A U G G U U U G G C Anticodon 5 mrna Codons 3 staff.unila.ac.id/priyambodo
3 U A C 5 A U G 5 3 P site Large ribosomal subunit Initiator trna mrna GTP GDP E A 5 Start codon 3 5 3 mrna binding site Small ribosomal subunit Translation initiation complex Figure 17.17 1 A small ribosomal subunit binds to a molecule of mrna. In a prokaryotic cell, the mrna binding site on this subunit recognizes a specific nucleotide sequence on the mrna just upstream of the start codon. An initiator trna, with the anticodon UAC, base-pairs with the start codon, AUG. This trna carries the amino acid methionine (Met). 2 The arrival of a large ribosomal subunit completes the initiation complex. Proteins called initiation factors (not shown) are required to bring all the translation components together. GTP provides the energy for the assembly. The initiator trna is in the P site; the A site is available to the trna bearing the next amino acid. staff.unila.ac.id/priyambodo
TRANSCRIPTION TRANSLATION DNA mrna Ribosome Polypeptide Ribosome ready for next aminoacyl trna Amino end of polypeptide mrna 5 E P A site site 2 3 GTP 2 GDP 1 Codon recognition. The anticodon of an incoming aminoacyl trna base-pairs with the complementary mrna codon in the A site. Hydrolysis of GTP increases the accuracy and efficiency of this step. E E P A P A 3 Translocation. The ribosome translocates the trna in the A site to the P site. The empty trna in the P site is moved to the E site, where it is released. The mrna moves along with its bound trnas, bringing the next codon to be translated into the A site. GDP GTP E P A 2 Peptide bond formation. An rrna molecule of the large subunit catalyzes the formation of a peptide bond between the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site. This step attaches the polypeptide to the trna in the A site. staff.unila.ac.id/priyambodo
The final stage of translation is termination When the ribosome reaches a stop codon in the mrna Release factor Free polypeptide 5 Stop codon (UAG, UAA, or UGA) 1 When a ribosome reaches a stop 2 The release factor hydrolyzes 3 The two ribosomal subunits codon on mrna, the A site of the the bond between the trna in and the other components of ribosome accepts a protein called the P site and the last amino the assembly dissociate. a release factor instead of trna. acid of the polypeptide chain. The polypeptide is thus freed from the ribosome. Figure 17.19 staff.unila.ac.id/priyambodo 3 5 3 5 3
Heme -Globin Hemoglobin -Globin -Globin gene family -Globin gene family Chromosome 16 Chromosome 11 2 1 2 1 G A Embryo Fetus and adult Embryo Fetus Adult staff.unila.ac.id/priyambodo
No. Pembeda Prokariotik Eukariotik 1 Promoter & mrna Polisistronik Monosistronik 2 DNA Coding Region Tidak dijumpai intron Dijumpai intron 3 RNA Polymerase 1 macam 3 macam 4 Proses Inisiasi transkripsi Hanya memerlukan RNA polimerase Membutuhkan protein lain 5 Post transkripsional Tidak ada Ada 6 Proses translasi Simultan Non simultan staff.unila.ac.id/priyambodo