GeneGene

Entire nucleic acid sequence necessary for the Entire nucleic acid sequence necessary for the synthesis of a functional polypeptide (protein chain) synthesis of a functional polypeptide (protein chain)

or functional RNAor functional RNA

Nucleic Acid Sequence

1. DNA (Deoxyribo Nucleic Acid)

2. RNA (Ribo Nucleic Acid)

DNA as Genetic MaterialDNA as Genetic Material

DNA encodes all the information in the cell The composition of the DNA is the same in all cells within an

organism Variation among different cells is achieved by reading the

DNA differently DNA contains four bases that encode all the information to make

an organism’s life

How is Information Encoded in DNA?

How is Information Encoded in DNA?

DNA Consists of four kinds of bases (A,C,G,T) joined to a sugar phosphate backbone

Bases carry the genetic information while the phosphate backbone is structural

Two complementary strands of bases (C-G) and (A-T)

DNA is a Polymer of Deoxyribonucleotide Units

DNA is a Polymer of Deoxyribonucleotide Units

DEOXYRIBONUCLEOTIDE

DEOXY RIBO NUCLEOTIDE

Deoxyribonucleic Acid Deoxyribonucleic Acid (DNA)(DNA)

NucleotideNucleotide:: Phosphate groupPhosphate group 5-carbon sugar5-carbon sugar

Nitrogenous baseNitrogenous base

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)

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

DNA is Composed of Four Different RibonucleotidesDNA is Composed of Four Different Ribonucleotides

HN

CHN

C

CN

CN

C

NH2

HHN

CHN

C

CN

CN

C

O

H2N

H

NC

CC

HN

C

O

CH3

HO

H

NC

CC

N

CH

O

H

H

NH2

Adenine Guanine

Thymine Cytosine

TwoPurines

TwoPyrimidines

9 9

1 1

Nitrogenous BasesNitrogenous Bases

PURINESPURINES

1.1. Adenine (A)Adenine (A)

2.2. Guanine (G)Guanine (G)

PYRIMIDINESPYRIMIDINES

3.3. Thymine (T)Thymine (T)

4.4. Cytosine (C)Cytosine (C)T or C

A or G

BASE-PAIRINGSBASE-PAIRINGS

BaseBase # of # of

PurinesPurines PyrimidinesPyrimidines PairsPairs H-BondsH-Bonds

Adenine (A)Adenine (A) Thymine (T)Thymine (T) A = TA = T 2 2

Guanine (G)Guanine (G) Cytosine (C)Cytosine (C) C GC G 3 3

CG

3 H-bonds

BASE-PAIRINGSBASE-PAIRINGS

CG

H-bonds

T A

Base Pairing Occurs Through Hydrogen Bonds

Base Pairing Occurs Through Hydrogen Bonds

A-TG-C

Chargaff’s RuleChargaff’s Rule

AdenineAdenine must pair with must pair with ThymineThymine

GuanineGuanine must pair with must pair with CytosineCytosine

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

G CT A

Backbone Sugar Molecules

Deoxyribose (DNA) Ribose (RNA)

O

OH

H

OH

H

H

H

HOCH2

HO

OH

OH

H

H

H

HOCH2

HO H

1´

2´3´

4´

5´

1´

2´3´

4´

5´

Ribose= Five Carbon Sugar Molecule

Deoxy ribo nucleotide

The DNA Backbone is a Deoxyribose Polymer

The DNA Backbone is a Deoxyribose Polymer

Deoxyribose sugars are linked by Phosphodiester Bonds

O

P O

O

O-

H2C

O-

O-

OH

OH

H

H

HH

H2C

H2C

HH

H

H

OHH

O

O

P O

O

O

OP

O HH

H

H

OHH

O

HO

5´

3´

5´

5´

3´

3´

2´

2´

2´

1´

1´

1´

5´-p 3´-OH

5´ 3´

5´

3´

5´

3´ 5´

3´O

P O

O

O-

H2C

O-

O-

OH

OH

H

H

HH

H2C

H2C

HH

H

H

OHH

O

O

P O

O

O

OP

O HH

H

H

OHH

O

HO

5´

3´

5´

5´

3´

3´

2´

2´

2´

1´

1´

1´

O

P O

O

O-

H2C

O-

O-

OH

OH

H

H

HH

H2C

H2C

HH

H

H

OHH

O

O

P O

O

O

OP

O HH

H

H

OHH

O

HO

5´

3´

5´

5´

3´

3´

2´

2´

2´

1´

1´

1´

Base

Base

Base

O

P O

O

O-

H2C

O-

O-

OH

OH

H

H

HH

H2C

H2C

HH

H

H

OHH

O

O

P O

O

O

OP

O HH

H

H

OHH

O

HO

5´

3´

5´

5´

3´

3´

2´

2´

2´

1´

1´

1´

NCH

N

NHCN

NH2

O

H

H

HHO

H

H

OCH2PO

O

PO

O

P

O- O-O-

O-

O

(dATP)

Deoxyadenosine 5´-triphosphateO

H

H

HHO

H

H

NCH

N

NHCN

NH2

HOCH2

DeoxyRibonucleotide

DeoxyRibonucleoside Deoxyadenosine

5´

3´ 5´

3´

NC

CC

N

CH

O

H

NH2

NC

CC

HN

C

O

CH3

HO

NC

CC

HN

C

O

CH3

HO

HO

OH

H

H

HHO

P O

O

O

OP

O

OH

H

H

HH

H2C

H2C

HH

H

H

HO

O-

O-

H2C

O-

O

OP

O

T

C

T

A

G

A

=

G C

A T

Double-stranded DNA Forms a Double Helix

Double-stranded DNA Forms a Double Helix

Central Dogma of BiologyCentral Dogma of Biology

DNA, RNA, and the Flow of Information

DNA, RNA, and the Flow of Information

TranslationTranscription

Replication

Central Dogma (Modifications)Central Dogma (Modifications)

Transcription TranslationDNA

(1) Reverse transcription

Replication

RNA

(2)Self Replication

Protein

(3)Self Replication

(2)Ribozymes

RNARNA

A polymer composed of nucleotides that contain A polymer composed of nucleotides that contain the sugar ribose and one of the four bases the sugar ribose and one of the four bases cytosine, adenine, guanine and uracilecytosine, adenine, guanine and uracile

Polynucleotide containing ribose sugar and uracil Polynucleotide containing ribose sugar and uracil instead of thymineinstead of thymine

Genetic material of some virusesGenetic material of some viruses Primary agent for transferring information from Primary agent for transferring information from

the genome to the protein synthetic machinerythe genome to the protein synthetic machinery

RNARNA NUCLEIC ACID, NUCLEIC ACID, SINGLE STRAND,SINGLE STRAND,

PO4, PO4, RIBOSE SUGAR.RIBOSE SUGAR. BASE PAIRS (N):BASE PAIRS (N):

U = URACILU = URACIL A=ADENINEA=ADENINE C=CYTOSINEC=CYTOSINE G=GUANINEG=GUANINE

URACIL(U)

base with a single-ring structure

phosphate group

sugar (ribose)

Types of RNATypes of RNA

Three types ofThree types of RNARNA::

A.A. messenger RNA (mRNA)messenger RNA (mRNA)

B.B. transfer RNA (tRNA)transfer RNA (tRNA)

C.C. ribosome RNA (rRNA)ribosome RNA (rRNA)

Remember: all produced in the Remember: all produced in the nucleusnucleus!!

A. Messenger RNA A. Messenger RNA (mRNA)(mRNA)

Carries the information for a specific Carries the information for a specific proteinprotein..

Made up of 500 to 1000 Made up of 500 to 1000 nucleotides nucleotides long.long.

Made up of Made up of codons codons ((sequence of three bases: AUG - sequence of three bases: AUG - methioninemethionine).).

Each Each codoncodon, is specific for an , is specific for an amino acidamino acid..

A. Messenger RNA A. Messenger RNA (mRNA)(mRNA)

methionine glycine serine isoleucine glycine alanine stopcodon

proteinprotein

A U G G G C U C C A U C G G C G C A U A AmRNAmRNA

startcodon

Primary structure of a proteinPrimary structure of a protein

aa1 aa2 aa3 aa4 aa5 aa6

peptide bonds

codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1

B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)

Made up of 75 to 80 nucleotides long.Made up of 75 to 80 nucleotides long. Picks up the appropriate Picks up the appropriate amino acid amino acid floating in the floating in the

cytoplasm (cytoplasm (amino acid activating enzymeamino acid activating enzyme)) Transports Transports amino acids amino acids to the to the mRNAmRNA.. Have Have anticodonsanticodons that are complementary to that are complementary to mRNAmRNA

codonscodons.. Recognizes the appropriate Recognizes the appropriate codonscodons on the on the mRNAmRNA and and

bonds to them with H-bonds.bonds to them with H-bonds.

codon in mRNA

anticodon

amino acid OH

amino acidattachment site

anticodon

tRNA MOLECULE

amino acid attachment site

The structure of transfer RNA (tRNA)The structure of transfer RNA (tRNA)

B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)

amino acidamino acidattachment siteattachment site

U A C

anticodonanticodon

methionine amino acidamino acid

C. Ribosomal RNA (rRNA)C. Ribosomal RNA (rRNA)

Made up of Made up of rRNArRNA is 100 to 3000 nucleotides long. is 100 to 3000 nucleotides long. Important structural component of a Important structural component of a ribosome.ribosome.

Associates with Associates with proteins proteins to form to form ribosomes.ribosomes.

RibosomesRibosomes

Large and small subunits.Large and small subunits.

Composed of Composed of rRNA (40%) rRNA (40%) and and proteins (60%).proteins (60%).

Both units come together and help bind the Both units come together and help bind the mRNAmRNA and and tRNA.tRNA.

Two sites forTwo sites for tRNAtRNA

a.a. P site P site (first and last (first and last tRNA will attachtRNA will attach))b.b. A site A site

RibosomesRibosomesOriginOrigin CompletComplet

e e ribosomribosomee

RibosomRibosomal al subunitsubunit

rRNA rRNA componentcomponentss

ProteinsProteins

Cytosol Cytosol (eukaryotic (eukaryotic ribosome)ribosome)

80 S80 S 40 S40 S

60 S60 S18 S18 S

5 S5 S

5.8 S5.8 S

25 S25 S

C.30C.30

C.50C.50

ChloroplastChloroplasts s (prokaryotic (prokaryotic ribosome)ribosome)

70 S70 S 30 S30 S

50 S50 S16 S16 S

4.5 S4.5 S

5 S5 S

23 S23 S

C. 24C. 24

C. 35C. 35

MtochondriMtochondrion on (prokaryotic (prokaryotic ribosome)ribosome)

78 S78 S 30 S30 S

50 S50 S18 S18 S

5 S5 S

26 S26 S

C. 33C. 33

C. 35C. 35

RibosomesRibosomes

PSite

ASite

Largesubunit

Small subunit

mRNAmRNA

A U G C U A C U U C G