Download PERAN GEN DALAM PERKEMBANGAN

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
• 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
Donor
cell
Nucleus from
donor cell
Remove
nucleus
from egg
cell
Add somatic
cell from
adult donor
Implant blastocyst
in surrogate mother
Clone of donor
is born
(REPRODUCTIVE
cloning)
Remove embryonic
stem cells from
blastocyst and
grow in culture
Induce stem
cells to form
specialized cells
for THERAPEUTIC
use
Grow in culture to produce
an early embryo (blastocyst)
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
• 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
Active
repressor
Protein
OPERON TURNED OFF (lactose absent)
DNA
RNA polymerase
bound to promoter
mRNA
Protein
Lactose
Inactive
repressor
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
• An overview of cellular respiration
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolsis
Pyruvate
Glucose
Cytosol
Mitochondrion
ATP
Figure 9.6
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Substrate-level
phosphorylation
ATP
Substrate-level
phosphorylation
ATP
Oxidative
phosphorylation
1
When blood glucose
level rises, a gland called
the pancreas secretes insulin,
a hormone, into the blood.
2
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.
STIMULUS:
Blood glucose
level rises
after eating.
Homeostasis:
90 mg glucose/
100 mL blood
4
Glucagon promotes
the breakdown of
glycogen in the
liver and the
release of glucose
into the blood,
increasing blood
glucose level.
STIMULUS:
Blood glucose
level drops
below set point.
3
When blood glucose
level drops, the pancreas
secretes the hormone
glucagon, which opposes
the effect of insulin.
• 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
• 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)
Histones
“Beads on
a string”
Nucleosome
(10-nm diameter)
Tight helical fiber
(30-nm diameter)
Supercoil
(200-nm diameter)
700
nm
Metaphase chromosome
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
X chromosomes
Allele for
orange fur
Allele for
black fur
Active X
Inactive X
Inactive X
Active X
Orange fur
Black fur
Chromosome
DNA unpacking
Other changes
to DNA
GENE
GENE
TRANSCRIPTION
Exon
RNA transcript
Intron
Addition of
cap and tail
Splicing
Tail
Cap
mRNA in nucleus
NUCLEUS
Flow
through
nuclear envelope
mRNA in cytoplasm
CYTOPLASM
Breakdown of mRNA
Translation
Broken-down mRNA
Polypeptide
Cleavage/modification/
activation
ACTIVE PROTEIN
Breakdown
of protein
Broken-down protein
The Control of Gene
Expression
• Mutant fruit flies show
the relationship
between gene
expression and
development
– Some mutants have
legs where antennae
should be
Eye
Antenna
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
Egg cell
Egg protein
signaling
follicle cells
1
Follicle
cells
2
Gene expression in
follicle cells
Follicle cell
protein signaling
egg cell
Localization of
“head” mRNA
3
“Head”
mRNA
ZYGOTE
FERTILIZATION
AND MITOSIS
EMBRYO
Translation of
“head” mRNA
Gradient of
regulatory
protein
4
Gene
expression
5
Gradient of
certain other
proteins
Gene
expression
Body
segments
6
EMBRYO
Body
segments
6
LARVA
Gene expression
ADULT FLY
7
Head end
Tail end
SIGNALING CELL
A signal-transduction
pathway that turns on a gene
1
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
Signal
molecule
Receptor
protein
Plasma
membrane
SIGNALING CELL
Signal
molecule
1
(3) Binding activates the first
relay protein, which then
activates the next relay
protein, etc.
2
Plasma
membrane
3
TARGET CELL
Relay
proteins
Transcription factor
(activated)
(4) The last relay protein
activates a transcription
factor
Receptor
protein
4
SIGNALING CELL
Signal
molecule
1
Receptor
protein
2
(5) The transcription factor
triggers transcription of a
specific gene
Plasma
membrane
3
TARGET CELL
Relay
proteins
Transcription factor
(activated)
(6) Translation of the mRNA
produces a protein
4
NUCLEUS
DNA
5
Transcription
mRNA
New
protein
6
Translation
1. Gen merupakan materi genetik yang
dapat diturunkan pada keturunannya
2. Plasmid adalah bakteri ekstrakromosomal yang dapat bereplikasi
3. Gen yang terdapat dibagian intron
dapat diterjemahkan dalam proses
transkripsi
4. Urutan sintesis protein dimulai dari
replikasi DNA, transkripsi, dan
translasi
5. Ekspresi gen diaktifkan oleh adanya
perubahan lingkungan
6. Transplantasi inti sel dewasa pada sel
telur, maka sel telur dapat
berkembang menjadi embrio
A
1. Perbanyakan sel (kloning) dapat
dilakukan dengan transformasi inti sel
somatik
2. Plasmid adalah protein ekstrakromosomal yang dapat bereplikasi dan
dapat ditemukan pada sel hidup
3. Transkripsi untuk menghasilkan protein
terjadi di sitoplasma sel
4. Gen yang terdapat dibagian ekson dapat
diterjemahkan dalam proses transkripsi
5. Pengaturan gen ditentukan oleh interaksi
hubungan sel ke sel
6. 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