Struktur dna

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1 Polinukleotida (Struktur DNA) copyright cmassengale

Transcript of Struktur dna

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Polinukleotida(Struktur DNA)

copyright cmassengale

DNA

• Material genetik pada mahluk hidup adalah Asam nukleat (DNA atau RNA)yaitu suatu polimer nukleotida yg berperanan dlm penyimpanan serta pemindahan informasi genetik

Bukti bahwa DNA adalah material

genetik

Transformation• Fred Griffith menggunakan strain

bakteri S.pneumoniae virulen tipe S and nonvirulent tipe R

Smooth Streptococcus

pneumoniae (pneumococci)

Rough Streptococcus

pneumoniae (pneumococci)

台大農藝系 遺傳學601 20000

Chapter 2 slide 5

Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

Griffith’s transformation experiment

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Transformation• Dia menemukan bhw strain tipe R

dapat menjadi virulent ketika mengambil DNA (transformasi) dari strain tipe S yg sudah mati

• Penelitian ini menunjukkan bahwa DNA adalah adalah material genetik

Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

Oswald T. Avery’s Transformation Experiment - 1944

Determined that “IIIS” DNA was the genetic material responsible for Griffith’s results (not RNA).

Support for Avery

• Alfred Hershey and Martha Chase- in 1952, used bacteriophage (T2) as a model.

Fig. 16.3

Structure of Viruses

• bacterial viruses may have tails and related structures

T4

virus

Structure of Viruses

Support for Avery

• They radiolabeled the protein coat with 35S and the DNA with 32P in order to “see” which of the molecules actually entered the cell and produced more phage.

Fig. 16.4: Hershey-Chase Exp.

DNA/RNA

• Asam nukleat terdapat dlm 2 bentuk, yaitu asam deoksiribosa (DNA) dan asam ribosa (RNA).

• Pd sel eukariot, DNA terdapat di dlmnukleus,

• pada sel prokariot, terdpt dlmsitoplasma dalam bentuk nukleoid.

StrukturDNA

DNATersusun atas subunit ygdisebut nukleotidaNukleotida terdiri atas: Gugus phosphate Gula berkarbon-5 Basa Nitrogen

DNA• Gula pentose (Deoxyribose) terikat ke gugus phosphat (PO4) groups melalui ikatan phosphodiester

• Ikatan antara molekul deoxiribosa dengan basa-basa nitrogen disebut ikatan glikosida

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Nukleotida DNA

O=P-OO

PhosphateGroup

NNitrogenous base(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

Sugar(deoxyribose)

O

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Gula Pentosa• Tersusun atas 5 atom karbon yg

dinotasi 1’ - 5’

CH2

O

C1C4

C3 C2

5

Sugar(deoxyribose)

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Basa2 Nitrogen

• Double ring PURINAdenine (A)Guanine (G)

• Single ring PYRIMIDINThymine (T)Cytosine (C) T or C

A or G

Pasangan-basa• Purin hanya berpasangan dgn Pirimidin

• Pasangan antara Guanin & sitosin membentuk tiga ikatan hidrogen

CG

3 H-bonds

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T A

•Pasangan antara Timin & Adenin membentuk dua ikatan hidrogen

Ikatan Hidrogen

H

H

H H

O

O

H

C

C

C C

N

N

C

TiminH

N

H

H

N

C C

C

C

N

N H

N

C

Adenin

H

O

N

H C

C C

N

N

C

Sitosin

H

H

H

N

C C

C

C

N

N H

N

C

Guanin

NH

O

H

5’ end

3’ end

Perbedaan DNA dan RNA

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DNA (Polinukleotida)

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

Three Dimensional Structure of DNA

• Rosalind Franklin- X-ray crystallography of DNA- showed that DNA was in a helix with PO4 and sugars to the outside.

• James Watson and Francis Crick-took Franklin’s data- in April 23, 1953, and deduced the structure of DNA. Won the Nobel Prize along with Maurice Wilkins.

1962: Nobel Prize in Physiology and Medicine

James D.Watson

Francis H.Crick

Maurice H. F.Wilkins

What about?Rosalind Franklin

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Untai ganda ygbersifat Antiparalel

• Satu untai tumbuh dari

5’ ke 3’ (gula)

• Untai yang lain memiliki arah yg berlawanan dari 3’ ke 5’

5’ end

3’ end

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DNA Double Helix

NitrogenousBase (A,T,G or C)

“Rungs of ladder”

“Legs of ladder”

Phosphate &Sugar Backbone

Type A, B, and Z conformations of DNA

Type B-DNA

Other DNA forms include:

A-DNA:Right-handed double helix with 11 bases per turn; shorter and wider at 2.2 nm diameter. Exists in some DNA-protein complexes.

Z-DNA:Left-handed double helix with 12 bases per turn; longer and thinner at 1.8 nm diameter.

Characteristics of DNA

• All chains of DNA and RNA have a 5’ PO4 end and a 3’ OH end.

• Base sequences are written in a 5’ to 3’ direction.

• Ex. 5’ pGpTpCpCpApT-OH 3’ or

- GTCCAT -

Characteristics of DNA

• Base pairs stabilize the molecule by forming H-bonds.

• Antiparallel Strands-

5’----------------3’

3’----------------5’

• Strands are complementary.

Discovery of DNA Structure

• Erwin Chargaff menunjukkan jumlah dari basa penyusun DNA ( A,T,C,G)

• Pada sel somatik:A = 30.3%T = 30.3%G = 19.5%C = 19.9%

Genome: Keseluruhan gen/DNA yang ada di

dalam sel hidup.

Gene:Urutan nukleotida yang mengkode

suatu protein.

Two types of organism: Eukaryotes;

cells contain membrane-bound

compartments, including a nucleus and organelles.

Eukaryotes include: animals, plants, fungi, and

protozoa.

Prokaryotes: Lack internal compartments

extensively.

Divided into two groups: bacteria and archaea.]

5’5’3’

3’

exon exonintronupstream downstream

Initiation codon termination codon

Gene organization in genomes

Circular shape of microbial DNA

台大農藝系 遺傳學601 20000

Chapter 2 slide 44

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