PERAN GEN DALAM PERKEMBANGAN

Para peneliti mengklon hewan melalui transplantasi inti Inti sel telur digantikan oleh inti sel somatik dewasa Sejauh ini, kloning pada manusia belum berhasil hingga menghasilkan embrio kurang dari 6 sel Perkembangan embrio ditentukan oleh ekspresi gen

Untuk terapi, kloning dihasilkan dari stem sel embrionik Dalam reproduksi eukariota secara kloning, embrio diimplantasikan di induknya Untuk terapi, kloning dihasilkan dari stem sel embrionik Stem cells can help patients with damaged tissues

Remove nucleus from egg cell Donor cell Add somatic cell from adult donor Grow in culture to produce an early embryo (blastocyst) Nucleus from donor cell Implant blastocyst in surrogate mother Remove embryonic stem cells from blastocyst and grow in culture Clone of donor is born (REPRODUCTIVE cloning) Induce stem cells to form specialized cells for THERAPEUTIC use

GENE REGULATION IN PROKARYOTES

Interaksi protein dan DNA pada gen prokariotik: on-off tergantung pada respon perubahan lingkungan Aliran informasi genetik dari gen ke protein disebut dengan ekspresi gen Penjelasan awalnya menggunakan pengaturan gene dari bakteri E. coli

Pada prokariot, gen berperan sebagai enzim, pengaturannya secara bersama menjadi unit pengaturan yang disebut operon Pengaturan pengikatan protein yang mengontrol urutan DNA dan on-off kerja operon diatur oleh perubahan lingkungan

Enzymes for lactose utilization Operon lac akan menghasilkan enzim untuk mengurai laktose jika ada laktose OPERON Regulatory gene Promoter Operator Lactose-utilization genes DNA mRNA RNA polymerase cannot attach to promoter Protein Active repressor OPERON TURNED OFF (lactose absent) DNA RNA polymerase bound to promoter mRNA Protein Inactive repressor Lactose Enzymes for lactose utilization OPERON TURNED ON (lactose inactivates repressor)

Dua tipe repressor yang dikontrol oleh operon Promoter Operator Genes DNA Active repressor Active repressor Tryptophan Inactive repressor Inactive repressor Lactose lac OPERON trp OPERON

Diferensiasi sel dan kloning eukariota Pada eukariota, sel menjadi spesifik seperti zigot berkembang menjadi organisme Tipe sel yang berbeda menyebabkan perbedaan macam protein penyusunnya Perbedaan kombinasi gen penyusun protein: aktif setiap tipe sel

Oxidative phosphorylation: electron transport and chemiosmosis An overview of cellular respiration Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol

1 When blood glucose level rises, a gland called the pancreas secretes insulin, a hormone, into the blood. Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen. As a result, blood glucose level drops. 2 STIMULUS: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood level drops below set point. Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose level. 4 When blood glucose level drops, the pancreas secretes the hormone glucagon, which opposes the effect of insulin. 3

Awal eksperimen: transplantasi inti sel hewan (katak) Kloning larva katak: inti sel somatik berpotensi genetik dan berkembang menjadi embrio selanjutnya larva katak Tadpole (frog larva) Frog egg cell Nucleus UV Intestinal cell Nucleus Transplantation of nucleus Nucleus destroyed Tadpole Eight-cell embryo

The first mammalian clone, a sheep named Dolly, was produced in 1997 Dolly provided further evidence for the developmental potential of cell nuclei

Reproductive cloning of nonhuman mammals has applications in basic research, agriculture, and medicine Scientists clone farm animals with specific sets of desirable traits Piglet clones might someday provide a source of organs for human transplant

stem sel dapat diperbanyak dan dapat digunakan untuk terapi setelah mengalami diferensiasi sel Stem sel dewasa dapat di kultur dan mengalami diferensiasi Diferensiasi sel dipengaruhi oleh perubahan media kultur

Cultured embryonic stem cells Differentiation of embryonic stem cells in culture Liver cells Cultured embryonic stem cells Nerve cells Heart muscle cells Different culture conditions Different types of differentiated cells

GENE REGULATION IN EUKARYOTES

DNA packing in eukaryotic chromosomes helps regulate gene expression A chromosome contains a DNA double helix wound around clusters of histone proteins DNA packing tends to block gene expression

DNA double helix (2-nm diameter) Metaphase chromosome 700 nm Tight helical fiber (30-nm diameter) Nucleosome (10-nm diameter) Histones “Beads on a string” Supercoil (200-nm diameter)

In female mammals, one X chromosome is inactive in each cell An extreme example of DNA packing in interphase cells is X chromosome inactivation EARLY EMBRYO TWO CELL POPULATIONS IN ADULT Cell division and X chromosome inactivation Active X Orange fur X chromosomes Inactive X Inactive X Allele for orange fur Black fur Active X Allele for black fur

Chromosome GENE RNA transcript mRNA in nucleus mRNA in cytoplasm Polypeptide ACTIVE PROTEIN Exon Intron Tail Cap NUCLEUS Flow through nuclear envelope CYTOPLASM Breakdown of mRNA Translation Broken-down mRNA Broken-down protein Cleavage/modification/ activation Breakdown of protein DNA unpacking Other changes to DNA TRANSCRIPTION Addition of cap and tail Splicing

The Control of Gene Expression

Head of a normal fruit fly Head of a developmental mutant Mutant fruit flies show the relationship between gene expression and development Eye Antenna Some mutants have legs where antennae should be Head of a normal fruit fly Leg Head of a developmental mutant

• Development of head-tail polarity in fruit fly EGG CELL WITHIN OVARIAN FOLLICLE 1 Egg cell Egg protein signaling follicle cells Gene expression in follicle cells Follicle cell protein signaling egg cell Localization of “head” mRNA 2 3 “Head” mRNA Follicle cells

FERTILIZATION AND MITOSIS ZYGOTE EMBRYO Translation of “head” mRNA Gradient of regulatory protein 4 Gene expression Gradient of certain other proteins 5 Gene expression Body segments 6

EMBRYO Body segments 6 LARVA Gene expression ADULT FLY 7 Head end Tail end

A signal-transduction pathway that turns on a gene SIGNALING CELL Signal molecule A signal-transduction pathway that turns on a gene 1 Plasma membrane Receptor protein 2 TARGET CELL (1) The signaling cell secretes the signal molecule (2) The signal molecule binds to a receptor protein in the target cell’s plasma membrane

(4) The last relay protein activates a transcription factor SIGNALING CELL Signal molecule 1 Plasma membrane Receptor protein 2 (3) Binding activates the first relay protein, which then activates the next relay protein, etc. 3 TARGET CELL Relay proteins 4 Transcription factor (activated) (4) The last relay protein activates a transcription factor

(5) The transcription factor triggers transcription of a specific gene SIGNALING CELL Signal molecule 1 Plasma membrane Receptor protein 2 (5) The transcription factor triggers transcription of a specific gene 3 TARGET CELL Relay proteins 4 Transcription factor (activated) (6) Translation of the mRNA produces a protein NUCLEUS DNA 5 Transcription mRNA New protein 6 Translation

Gen merupakan materi genetik yang dapat diturunkan pada keturunannya Plasmid adalah bakteri ekstra- kromosomal yang dapat bereplikasi Gen yang terdapat dibagian intron dapat diterjemahkan dalam proses transkripsi Urutan sintesis protein dimulai dari replikasi DNA, transkripsi, dan translasi Ekspresi gen diaktifkan oleh adanya perubahan lingkungan Transplantasi inti sel dewasa pada sel telur, maka sel telur dapat berkembang menjadi embrio A Perbanyakan sel (kloning) dapat dilakukan dengan transformasi inti sel somatik Plasmid adalah protein ekstra- kromosomal yang dapat bereplikasi dan dapat ditemukan pada sel hidup Transkripsi untuk menghasilkan protein terjadi di sitoplasma sel Gen yang terdapat dibagian ekson dapat diterjemahkan dalam proses transkripsi Pengaturan gen ditentukan oleh interaksi hubungan sel ke sel Stem sel dewasa dapat di kultur dan mengalami diferensiasi B

KEY A 1. B 2. S (DNA) 3. S (akson) 4. B 5. B 6.B B 1. S (transplantasi) 2. S (DNA) 3. S (inti) 4. B 5. B 6.B