konsep dasar genetika
DESCRIPTION
dasar-dasar pengenalan genetikaTRANSCRIPT
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Dr. Niken Satuti Nur Handayani, M.Sc.Dr. Budi Setiadi Daryono, M.Agr.Sc.Ganies R A, S.Si., M.Sc.
GENETIKA BIO 3041
Pendahuluan; Akses on-line books ; Konsep Dasar Genetika;
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The National Center for Biotechnology Information
NCBI Bookshelf
www.ncbi.nlm.nih.gov/books/bv.fcgi
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1. What is the center of heredity in a cell?2. What is genetic material?3. What is a gene?4. What is a chromosome?5. When and how can chromosomes be visualized?6. How many chromosomes does an organism have?7. What is accomplished during the process of mitosis and
meiosis?8. What are the sources of genetic variation?9. How does DNA store genetic information?10. How is genetic code organized?11. How is genetic code expressed?12. Why are proteins so important to living organisms that they
serve as the end product of the vast majority of genes?
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DNA Sequence(splited by genes)
RNA phenotypeproteinAmino Acidsequence
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Before a cell can divide, it must replicate all its DNA.
From one end, the double helix is unwound, expose single bases on each strand.
Each strand works as a template to reform a new double helix.
The new double helix is formed by strict base pairing requirement, i.e., A-T, C-G.
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DNAmolecule
Gene 1
Gene 2
Gene 3
DNA strand(template)
TRANSCRIPTION
mRNA
Protein
TRANSLATION
Amino acid
A C C A A A C C G A G T
U G G U U U G G C U C A
Trp Phe Gly Ser
Codon
3 5
35
During transcription
The gene determines the sequence of bases along the length of an mRNA molecule
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Translation of the nucleotide sequence on
mRNA
Determines the amino acid sequence by
genetic code
Genetic Code: three base pairs of RNA
(called a codon) determine one amino
acid based on a fixed table
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P : induk/orang tua/parental
berasal dari Bhs. Latin parens
F : keturunan
berasal dari Bhs. Latin filius
Fenotip
Genotip
Alel
Homozigot/Heterozygot
Diploid/Haploid
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Tingkat Biokimiawi Fenotip molekul protein, mis. fenotip globin
Aktifitas enzim, kadar gula darah Tingkat Fisiologis Hasil rekam elektrokardiografi, tekanan darah
Tingkat Histologis Variasi bentuk sel
Tingkat Anatomis Tinggi badan, warna kulit, warna rambut
Tingkat Psikologis Tingkah laku, IQ
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Hibrid
Persilangan Resiprok
Back-cross (Persilangan Kembali)
Test-cross (Uji Silang)
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GENETIKA (BIO 3041)Fakultas BiologiUniversitas Gadjah MadaSM Gasal TA 2011/12012
Dr. Niken Satuti Nur Handayani, M.ScLaboratorium Genetika, Fakultas Biologi [email protected]; [email protected]
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The role of DNA in heredity
Was first worked out by studying bacteria and the viruses that infect them
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Frederick Griffith was studying Streptococcus pneumoniae
A bacterium that causes pneumonia in mammals
He worked with two strains of the bacterium
A pathogenic strain and a nonpathogenic strain
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Griffith found that when he mixed heat-killed remains of the pathogenic strain
With living cells of the nonpathogenic strain, some of these living cells became pathogenic
Bacteria of the S (smooth) strain of Streptococcus pneumoniae are pathogenic because they have a capsule that protects them from an animals defense system. Bacteria of the R (rough) strain lack a capsule and are nonpathogenic. Frederick Griffith injected mice with the two strains as shown below:
Griffith concluded that the living R bacteria had been transformed into pathogenic S bacteria by anunknown, heritable substance from the dead S cells.
EXPERIMENT
RESULTS
CONCLUSION
Living S(control) cells
Living R(control) cells
Heat-killed(control) S cells
Mixture of heat-killed S cellsand living R cells
Mouse dies Mouse healthy Mouse healthy Mouse dies
Living S cellsare found inblood sample.
Figure 16.2
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Griffith called the phenomenon transformation
Now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell
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The Hershey-Chase experiment showed that certain viruses reprogram host cells to produce more viruses by injecting their DNA
THE STRUCTURE OF THE GENETIC MATERIAL
Head
Tail
Tailfiber
DNA
Campbell et al, 2003
Figure 10.1A
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The Hershey-Chase Experiment
Mix radioactivelylabeled phages with bacteria. The phages infect the bacterial cells.
1 2 Agitate in a blender to separate phages outside the bacteria from the cells and their contents.
3 Centrifuge the mixture so bacteria form a pellet at the bottom of the test tube.
4 Measure the radioactivity in the pellet and liquid.
Campbell et al, 2003
Figure 10.1B
Phage
Bacterium
Radioactiveprotein
DNA
Emptyprotein shell
Batch 1Radioactiveprotein
Batch 2RadioactiveDNA
RadioactiveDNA
PhageDNA
Centrifuge
Pellet
Radioactivityin liquid
Radioactivityin pelletPellet
Centrifuge
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Campbell et al, 2003
Figure 10.1C
Phage attaches to bacterial cell.
Phage injects DNA.
Phage DNA directs host cell to make more phage DNA and protein parts. New phages assemble.
Cell lyses and releases new phages.
The Hershey-Chase Experiment
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Prior to the 1950s, it was already known that DNA
Is a polymer of nucleotides, each consisting of three components: a nitrogenous base, a sugar, and a phosphate group
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DNA has four kinds of bases,A, T, C, and G
Campbell et al, 2003
Figure 10.2B
Pyrimidines
Thymine (T) Cytosine (C)
Purines
Adenine (A) Guanine (G)
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DNA is a nucleic acid, made of long chains of nucleotides
Campbell et al, 2003
Figure 10.2A
Nucleotide
Phosphate group
Nitrogenous base
Sugar
Polynucleotide Sugar-phosphate backbone
DNA nucleotide
Phosphategroup
Nitrogenous base(A, G, C, or T)
Thymine (T)
Sugar(deoxyribose)
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RNA is also a nucleic acid
RNA has a slightly different sugar
RNA has U instead of T
Figure 10.2C, D
Phosphategroup
Nitrogenous base(A, G, C, or U)
Uracil (U)
Sugar(ribose)
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Once most biologists were convinced that DNA was the genetic material
The challenge was to determine how the structure of DNA could account for its role in inheritance
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James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin
Figure 10.3A, B
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Hydrogen bonds between bases hold the strands together
Each base pairs with a complementary partner
A pairs with T
G pairs with C
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In DNA replication, the strands separate
Enzymes use each strand as a template to assemble the new strands
DNA REPLICATION
Parental moleculeof DNA
Figure 10.4A
Both parental strands serveas templates
Two identical daughtermolecules of DNA
Nucleotides
A
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Untwisting and replication of DNA
DNA replication is semiconservative
Each of the two new daughter molecules will have one old strand, derived from the parent molecule, and one newly made strand
Figure 16.10 ac
Conservativemodel. The twoparental strandsreassociate after acting astemplates fornew strands,thus restoringthe parentaldouble helix.
Semiconservativemodel. The two strands of the parental moleculeseparate, and each functionsas a templatefor synthesis ofa new, comple-mentary strand.
Dispersivemodel. Eachstrand of bothdaughter mol-ecules containsa mixture ofold and newlysynthesizedDNA.
Parent cell
Firstreplication
Secondreplication
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Each strand of the double helix is oriented in the opposite direction
Figure 10.5B
5 end 3 end
3 end 5 end
P
P
P
P
P
P
P
PThe molecular structure of DNA
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The molecular structure of DNA
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Figure 16.7a, c
C
T
A
A
T
CG
GC
A
C G
AT
AT
A T
TA
C
TA
0.34 nm
3.4 nm
(a) Key features of DNA structure
G
1 nm
G
(c) Space-filling model
T
Watson and Crick deduced that DNA was a double helix
Through observations of the X-ray crystallographic images of DNA
The molecular structure of DNA
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Franklin had concluded that DNA
Was composed of two antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecules interior
The nitrogenous bases
Are paired in specific combinations: adenine with thymine, and cytosine with guanine
The molecular structure of DNA
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Watson and Crick reasoned that there must be additional specificity of pairing
Dictated by the structure of the bases
Each base pair forms a different number of hydrogen bonds
Adenine and thymine form two bonds, cytosine and guanine form three bonds
The molecular structure of DNA
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N H O CH3
N
N
O
N
N
N
N H
Sugar
Sugar
Adenine (A) Thymine (T)
N
N
N
N
Sugar
O H N
H
NH
N OH
H
N
Sugar
Guanine (G) Cytosine (C)Figure 16.8
H
The molecular structure of DNA
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In eukaryotes, DNA is packaged with proteins to form a matrix called chromatin.
The DNA is coiled around bundles of eight or nine histone proteins to form DNA-histonecomplexes called nucleosomes.
Through the electron microscope, the nucleosomes appear like beads on a string.
During cell division, DNA is compactly organized into chromosomes.
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In the non-dividing cell, the DNA is arranged as either of two types of chromatin: Euchromatin describes regions where the DNA is
loosely bound to nucleosomes. DNA in these regions is actively being transcribed.
Heterochromatin represents areas where the nucleosomes are more tightly compacted, and where DNA is inactive.
Because of its condensed arrangement, heterochromatin stains darker than euchromatin.
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Erwin Chargaff analyzed the base composition of DNA from a number of different organisms
In 1947, Chargaff reported that DNA composition varies from one species to the next
This evidence of molecular diversity among species made DNA a more credible candidate for the genetic material
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Jumlah basa purine sebanding denganjumlah basa pyrimidine (A+G) = (C+T)
Jumlah basa adenine sebanding denganjumlah basa thymine A = T
Jumlah basa guanine sebanding denganjumlah basa cytosine G = C
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Contoh:Diketahui bahwa kandungan Adenin darimolekul DNA suatu makhluk hidup adalah 20%, maka:A = T (A = 20% ; T = 20%)A + T = 40%C + G = 100% - 40% = 60%, sehingga kandungan C = 30% dan G = 30%
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Nuclear; chromosomes
Nuclear genome; chromosomal DNA
Mitochondrion; Chloroplast
Extra-nuclear genome; extra-chromosomal DNA
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The following diagram displays the flow of genetic information from DNA to the protein. This can be interpreted in genetic terms by saying that information contained in genes (DNA) is eventually expressed as the phenotype (protein).
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In eukaryotes, chromosomes bear the genetic information that is passed from parents to offspring.
The genetic information is stored in molecules of DNA. The DNA, in turn, codes for enzymes, which, in turn, regulate chemical reactions that direct metabolism for cell development, growth, and maintenance.
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The nucleotide sequence of a DNA is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon?
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The base sequence of the gene coding for a short polypeptide is GATGCGATCCGCTAACTGATT. What would be the base sequence of the mRNA transcribed from this gene? Using the genetic code, give the amino acid sequence of the polypeptide translated from this mRNA!
(Hint: What is the start codon?)
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The base sequence of the template DNA strand for a short polypeptide is CTACGCTAGGCGATTGACTTT. What would be the base sequence of the mRNA transcribed from this gene? Using the genetic code, give the amino acid sequence of the polypeptide translated from this mRNA.