Structure of DNAStructure of DNA

An overviewAn overview

DNADNA contains the contains the blueprints or blueprints or codebook for lifecodebook for life Stores information for Stores information for

protein productionprotein production Proteins direct Proteins direct

cellular activity and cellular activity and determine determine characteristicscharacteristics

Located in the Located in the nucleusnucleus of eukaryotes of eukaryotes

Made up of units Made up of units called called nucleotidesnucleotides Consists of Consists of

deoxyribose, deoxyribose, phosphate groups, and phosphate groups, and N carrying baseN carrying base Bases are Bases are guanine guanine

(G), Cytosine (C), (G), Cytosine (C), Adenine (A), Adenine (A), Thymine (T)Thymine (T)

Shape is called a Shape is called a double helixdouble helix Outside is made of Outside is made of

alternating alternating phosphates and phosphates and sugar groupssugar groups

Inside is made of N Inside is made of N carrying basescarrying bases

Base-paring ruleBase-paring rule: : structure and size of structure and size of each of the Nitrogen each of the Nitrogen bases only allows the bases only allows the following pairingfollowing pairing

A pairs with TA pairs with T C pairs with GC pairs with G Bases of one strand of Bases of one strand of

DNA are DNA are complimentary to the complimentary to the otherother

Sequence of Sequence of Nucleotides is the Nucleotides is the code that controls code that controls the production of the production of

all proteinsall proteins

DNA REVIEWDNA REVIEWDNADNA

meansmeans Deoxyribonucleic AcidDeoxyribonucleic Acid

SugarSugar deoxyribosedeoxyribose

basebase GCATGCAT

# of strands# of strands TWOTWO

FunctionFunction Stores hereditary information and Stores hereditary information and codes for proteinscodes for proteins

The order:The order: DNA DNA transcription transcription RNA RNA translation translation protein protein

Copying DNACopying DNA

ReplicationReplication- the - the process of DNA process of DNA copying itselfcopying itself takes 6 -8 hourstakes 6 -8 hours is done BEFORE is done BEFORE

mitosis or meiosismitosis or meiosis

DNA is DNA is unzipped by unzipped by special special enzymes enzymes called called DNA DNA HelicasesHelicases break the break the H bonds H bonds between between the strandthe strand

replication forkreplication fork = =areas on either end of areas on either end of the DNA where the double helix is the DNA where the double helix is separated separated

occurs in a circle, not one end to another)occurs in a circle, not one end to another)

Once the DNA is partially unzipped, special Once the DNA is partially unzipped, special enzymes called enzymes called DNA PolymerasesDNA Polymerases move move along the exposed DNA making a along the exposed DNA making a complimentary strand for it.complimentary strand for it.

Enzymes stay Enzymes stay bonded to the bonded to the DNA until all of DNA until all of the DNA is the DNA is copiedcopied

Once the Once the copying is done, copying is done, you have 2 you have 2 identical strands identical strands of DNAof DNA

Polymerases are able to double check their Polymerases are able to double check their workwork Typically few errorsTypically few errors Approximately 1 per billion nucleotidesApproximately 1 per billion nucleotides

DNA’s instructions are DNA’s instructions are carried out by carried out by RNA RNA (ribonucleic acid)(ribonucleic acid) Acts as photocopier, Acts as photocopier,

copying genes copying genes Contains more H than Contains more H than

DNA doesDNA does Made of G, C, A and Made of G, C, A and U U

(Uracil)(Uracil) instead of T instead of T Is a Is a SINGLE SINGLE

STRANDEDSTRANDED molecule molecule

TranscriptionTranscription – transfer of instructions for – transfer of instructions for making a protein from a gene to RNA making a protein from a gene to RNA Done in nucleusDone in nucleus Similar to copying DNASimilar to copying DNA

RNA polymerase RNA polymerase binds binds to a gene’s promoter to a gene’s promoter (AUG sequence)(AUG sequence)

Unzips Unzips the DNAthe DNA Reads and copiesReads and copies the DNA using RNA base the DNA using RNA base

pairs (substitute U for T)pairs (substitute U for T) Reaches a Reaches a stopstop signal and the RNA is released signal and the RNA is released

TranslationTranslation – translates RNA base sequence into the Amino acid – translates RNA base sequence into the Amino acid sequence of a proteinsequence of a protein done in Ribosomesdone in Ribosomes begins at the UAG codebegins at the UAG code uses uses mRNAmRNA (messenger) to carry the code from the nucleus to (messenger) to carry the code from the nucleus to

the ribosomethe ribosome usesuses tRNA tRNA (transfer) to pick up the amino acid in the cytoplasm (transfer) to pick up the amino acid in the cytoplasm

and carries it to the ribosomeand carries it to the ribosome uses uses rRNA rRNA (ribosomal) to bind mRNA and tRNA(ribosomal) to bind mRNA and tRNA

The order:The order: DNA DNA transcription transcription RNA RNA translation translation protein protein

RNA REVIEWRNA REVIEWRNARNA

meansmeans ribonucleic Acidribonucleic Acid

SugarSugar riboseribose

basebase GCAUGCAU

# of strands# of strands OneOne

FunctionFunction Involved in protein synthesisInvolved in protein synthesis

DNA / RNA comparisonDNA / RNA comparisonmeansmeans Deoxyribonucleic AcidDeoxyribonucleic Acid ribonucleic Acidribonucleic Acid

SugarSugar deoxyribosedeoxyribose riboseribose

basebase GCATGCAT GCAUGCAU

# of strands# of strands TWOTWO OneOne

FunctionFunction Stores hereditary Stores hereditary information and codes information and codes for proteinsfor proteins

Involved in protein Involved in protein synthesissynthesis