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;

The National Center for Biotechnology Information

NCBI Bookshelf

www.ncbi.nlm.nih.gov/books/bv.fcgi

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?

DNA Sequence(splited by genes)

RNA phenotypeproteinAmino Acidsequence

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.

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

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

P : induk/orang tua/parental

berasal dari Bhs. Latin parens

F : keturunan

berasal dari Bhs. Latin filius

Fenotip

Genotip

Alel

Homozigot/Heterozygot

Diploid/Haploid

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

Hibrid

Persilangan Resiprok

Back-cross (Persilangan Kembali)

Test-cross (Uji Silang)

GENETIKA (BIO 3041)Fakultas BiologiUniversitas Gadjah MadaSM Gasal TA 2011/12012

Dr. Niken Satuti Nur Handayani, M.ScLaboratorium Genetika, Fakultas Biologi UGMnikensat@yahoo.com; niken_satuti@ugm.ac.id

The role of DNA in heredity

Was first worked out by studying bacteria and the viruses that infect them

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

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

Griffith called the phenomenon transformation

Now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell

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

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

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

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

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)

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)

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)

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

James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin

Figure 10.3A, B

Hydrogen bonds between bases hold the strands together

Each base pairs with a complementary partner

A pairs with T

G pairs with C

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

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

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

The molecular structure of DNA

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

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

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

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

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.

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.

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

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

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%

Nuclear; chromosomes

Nuclear genome; chromosomal DNA

Mitochondrion; Chloroplast

Extra-nuclear genome; extra-chromosomal DNA

50

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).

52

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.

54

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?

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?)

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.