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Ekayanti(3325095042)

Teguh Permana (3325100156)

Imanuelle Orchidea(3325102413)

DNA(Deoxyribonucleic Acid)

Genetic material of cells…Genetic material of cells…• GENES – units of genetic material that GENES – units of genetic material that

CODES FOR A SPECIFIC TRAITCODES FOR A SPECIFIC TRAIT

• Called Called NUCLEIC ACIDSNUCLEIC ACIDS

• DNA is made up of repeating molecules DNA is made up of repeating molecules called called NUCLEOTIDESNUCLEOTIDES

DNA stands for deoxyribose nucleic acid

This chemical substance is present in the nucleusof all cells in all living organisms

DNA controls all the chemical changes which take place in cells

The kind of cell which is formed, (muscle, blood,nerve etc) is controlled by DNA

The kind of organism which is produced (buttercup,giraffe, herring, human etc) is controlled by DNA

DNA 2

DNA Components

They are definitely inanimate compounds.

DNA is a very large molecule made up of a long chain of sub-units

The sub-units are called nucleotides

Each nucleotide is made up of

a sugar called deoxyribose

a phosphate group -PO4 and

an organic base

DNA molecule 3

DNA NucleotideDNA Nucleotide

OO=P-O O

PhosphatePhosphate GroupGroup

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

CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

A HISTORY OF DNAA HISTORY OF DNA

• Discovery of the DNA double helixDNA double helix

A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)

B. Rosalind Franklin - X-ray photo of DNA.(1952)

C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)

SEE p. 292-293

Watson & Crick proposed…Watson & Crick proposed…•DNA had specific pairing between the DNA had specific pairing between the

nitrogen bases:nitrogen bases:

ADENINEADENINE – – THYMINETHYMINE

CYTOSINECYTOSINE - - GUANINEGUANINE

•DNA was made of DNA was made of 22 long stands of long stands of nucleotides arranged in a specific way nucleotides arranged in a specific way

called the called the “Complementary Rule”“Complementary Rule”

Ribose is a sugar, like glucose, but with only fivecarbon atoms in its molecule

Deoxyribose is almost the same but lacks one oxygen atom

Both molecules may be represented by the symbol

Ribose & deoxyribose 4

The most common organic bases are

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

The bases 5

The deoxyribose, the phosphate and one of the bases

adenine

deoxyribose

PO4

Combine to form a nucleotide

Nucleotides 6

A molecule of DNA is formed by millions of nucleotides joined together in a long chain

PO4

PO4

PO4

PO4

sugar-phosphate backbone

+ bases

Joined nucleotides 7

In fact, the DNA usually consists of a double strand of nucleotides

The sugar-phosphate chains are on the outsideand the strands are held together by chemical bonds between the bases

8

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

2-stranded DNA 9

The bases always pair up in the same way

Adenine forms a bond with Thymine

and Cytosine bonds with Guanine

Bonding 1 10

Adenine Thymine

Cytosine Guanine

PO4

PO4

PO4

thymine

PO4

PO4

PO4

PO4

adenine

cytosine

PO4

guanine

Bonding 2 11

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

Pairing up 12

The paired strands are coiled into a spiral called

A DOUBLE HELIX

13

DNA Double HelixDNA Double Helix

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

DNA Double HelixDNA Double Helix

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

Nitrogenous BasesNitrogenous Bases• PURINESPURINES

1. Adenine (A)Adenine (A)

2. Guanine (G)Guanine (G)

• PYRIMIDINESPYRIMIDINES3. Thymine (T)Thymine (T)

4. Cytosine (C)Cytosine (C) T or C

A or G

Chargaff’s RuleChargaff’s Rule• AdenineAdenine must pair with ThymineThymine

• GuanineGuanine must pair with CytosineCytosine

• Their amounts in a given DNA molecule will be about the sameabout the same.

G CT A

BASE-PAIRINGSBASE-PAIRINGS

CG

H-bonds

T A

Genetic Diversity…Genetic Diversity…• Different Different

arrangements of arrangements of NUCLEOTIDESNUCLEOTIDES in a in a nucleic acid (DNA) nucleic acid (DNA) provides the key to provides the key to DIVERSITYDIVERSITY among among living organisms.living organisms.

The Code of Life…The Code of Life…• The “code” of the chromosome is the The “code” of the chromosome is the

SPECIFIC ORDERSPECIFIC ORDER that bases occur. that bases occur.

A T C G T A T G C G G…A T C G T A T G C G G…

Before a cell divides, the DNA strands unwind and separate

Each strand makes a new partner by addingthe appropriate nucleotides

The result is that there are now two double-stranded DNA molecules in the nucleus

So that when the cell divides, each nucleus contains identical DNA

This process is called replication

replication 16

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

The strands separate

17

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

Each strand builds up its partner by adding the appropriate nucleotides

18

The sequence of bases in DNA forms the Genetic Code

A group of three bases (a triplet) controlsthe production of a particular amino acid in the cytoplasm of the cell

The different amino acids and the order in which they are joined up determines the sort of protein being produced

Genetic code 1 19

Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly

Val- Cyst-Ala-Ala-Ser-Gly

This is a small, imaginary protein molecule showing how a sequence of 5 different amino acids could determine the shape and identity of the molecule

Each amino acid (Serine, Cysteine, Valine, Glycine and Alanine) is coded for by a particular triplet of bases

Genetic code 2 20

For example

Cytosine

Adenine Codes for Valine

Cytosine (C)

Guanine (G)

Adenine (A)

Codes for Alanine

Thymine

Coding 21

This is known as the triplet code

Each triplet codes for a specific amino acid

CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA -

Ala Val Gly Gly Arg Pro Leu Gly

Ala Val Gly Gly Arg Pro Leu Gly

The amino acids are joined together in the correct sequence to make part of a protein

Triplet code 22

The proteins build the cell structures

They also make enzymes

The DNA controls which enzymes are made andthe enzymes determine what reactions take place

The structures and reactions in the cell determinewhat sort of a cell it is and what its function is

So DNA exerts its control through the enzymes

DNA and enzymes 23

A sequence of triplets in the DNA molecule may code for a complete protein

Such a sequence forms a gene

There may be a thousand or more bases in one gene

Genes 24

DNA is wrapped tightly around histones and coiled tightly to form

chromosomes

See p. 297

DNA DNA ReplicationReplication• DNA must be copiedDNA must be copied

• The DNA molecule produces The DNA molecule produces 2 2 IDENTICALIDENTICAL new complementary new complementary strands following the rules of strands following the rules of base pairing: base pairing:

A-T, G-CA-T, G-C

•Each strand of the Each strand of the original DNA serves as original DNA serves as a template for the new a template for the new strand strand See p. 298See p. 298

DNA DNA ReplicationReplication• Semiconservative Semiconservative

Model:Model:1. Watson and Crick Watson and Crick showed:showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.

. Parental DNADNA Template

New DNA

(1961)(1961) Watson & Crick proposed… Watson & Crick proposed…• ……DNA controlled cell function by DNA controlled cell function by

serving as a template for serving as a template for PROTEINPROTEIN structure.structure.

• 3 Nucleotides = a triplet or 3 Nucleotides = a triplet or CODONCODON(which code for a specific AMINO ACID)(which code for a specific AMINO ACID)

• AMINO ACIDSAMINO ACIDS are the building blocks are the building blocks of proteins.of proteins.

DNA DNA TranscriptionTranscription• DNA can “unzip” DNA can “unzip”

itself and itself and RNARNA nucleotides match nucleotides match up to the DNA up to the DNA strand.strand.

• Both DNA & RNA Both DNA & RNA are formed from are formed from NUCLEOTIDESNUCLEOTIDES and and are called are called NUCLEICNUCLEIC acids.acids.

See p.301See p.301

DNA DNA TranslationTranslation• The cell uses The cell uses

information from information from “messenger” RNA “messenger” RNA to produce proteinsto produce proteins

AMAZING DNA FACTS…AMAZING DNA FACTS…• DNA from a single human DNA from a single human

cell extends in a single cell extends in a single thread for almost 2 meters thread for almost 2 meters long!!!long!!!

• It contains information It contains information equal to some 600,000 equal to some 600,000 printed pages of 500 words printed pages of 500 words each!!! each!!! (a library of about 1,000 books)(a library of about 1,000 books)