DNADNA

DNA is…DNA is…– Your genetic codeYour genetic code– What tells your cells which proteins to make What tells your cells which proteins to make

and when to make themand when to make them– The code that makes up your genesThe code that makes up your genes– Located on chromosomes (chromosomes are Located on chromosomes (chromosomes are

long strands of DNA)long strands of DNA)– What makes you who you areWhat makes you who you are– What makes you different from the 6 billion What makes you different from the 6 billion

other people on the planetother people on the planet– What enables your cells to have different forms What enables your cells to have different forms

and perform different functionsand perform different functions– Unique to youUnique to you

DNA is a nucleic acid (organic DNA is a nucleic acid (organic molecule)molecule)

DNA (as with all nucleic acids) are DNA (as with all nucleic acids) are made up of repeating subunits called made up of repeating subunits called nucleotidesnucleotides

Each DNA molecule is made up of 2 Each DNA molecule is made up of 2 long chains of nucleotideslong chains of nucleotides

DeoxyriboDeoxyribonucleicnucleic AcidAcid

DNA StructureDNA Structure

A DNA nucleotide has 3 partsA DNA nucleotide has 3 parts– A sugar molecule called A sugar molecule called deoxyribosedeoxyribose– A phosphate groupA phosphate group– A nitrogen-containing baseA nitrogen-containing base

The deoxyribose sugar and the The deoxyribose sugar and the phosphate group are identical in all phosphate group are identical in all DNA nucleotidesDNA nucleotides

Nitrogen base may be any one of four Nitrogen base may be any one of four different kindsdifferent kinds

Nitrogen basesNitrogen bases

The four nitrogen bases found in DNA The four nitrogen bases found in DNA nucleotides arenucleotides are– Adenine: AAdenine: A– Guanine: GGuanine: G– Cytosine: CCytosine: C– Thymine: TThymine: T

Purines: 2 rings of Carbon and Purines: 2 rings of Carbon and NitrogenNitrogen– AdenineAdenine– GuanineGuanine

Pyrimidine: 1 ring of Carbon and Pyrimidine: 1 ring of Carbon and NitrogenNitrogen– CytosineCytosine– ThymineThymine

Double HelixDouble Helix

James Watson and Frances CrickJames Watson and Frances Crick 2 nucleotide chains wrap around 2 nucleotide chains wrap around

each other to form a double spiral: a each other to form a double spiral: a double helixdouble helix

Complementary Base Complementary Base PairingPairing

Cytosine bonds Cytosine bonds with Guaninewith Guanine– C = GC = G

Adenine bonds Adenine bonds with Thyminewith Thymine– A = TA = T

A

AA

T

C

TG

A

T

G

C

T

A

Replication of DNAReplication of DNA

DNA must replicate in order to pass DNA must replicate in order to pass exact copies of its DNA to daughter exact copies of its DNA to daughter cellscells

Connected to each other with Connected to each other with Hydrogen BondsHydrogen Bonds

Cytosine and Guanine form 3 H Cytosine and Guanine form 3 H bondsbonds

Adenine and Thymine form 2 H Adenine and Thymine form 2 H bondsbonds

One nucleotide chain in DNA One nucleotide chain in DNA molecule is an exact complement of molecule is an exact complement of the nucleotide sequence of another the nucleotide sequence of another chainchain

DNA ReplicationDNA Replication

Replication: the process of copying Replication: the process of copying DNA in a cellDNA in a cell

The 2 nucleotide chains separate by The 2 nucleotide chains separate by unwindingunwinding

Each chain serves as a template for a Each chain serves as a template for a new nucleotide chainnew nucleotide chain

http://www.dnalc.org/resources/3d/http://www.dnalc.org/resources/3d/15-translation-basic.html15-translation-basic.html

11stst step: step:– Separate the 2 nucleotide chainsSeparate the 2 nucleotide chains

The point at which the 2 chains The point at which the 2 chains separate is called the replication fork separate is called the replication fork (think: a fork in a road is when a road (think: a fork in a road is when a road separates)separates)

The nucleotide chains are separated The nucleotide chains are separated by enzymes called by enzymes called helicaseshelicases

Helicase enzymes move along the Helicase enzymes move along the DNA molecules, breaking Hydrogen DNA molecules, breaking Hydrogen bonds between complementary bonds between complementary bases, and the chains separate.bases, and the chains separate.

DNA polymerase: enzymes that bind DNA polymerase: enzymes that bind to the separate chains of DNA for to the separate chains of DNA for copyingcopying

As polymerase moves along the As polymerase moves along the chains, new chains are assembled chains, new chains are assembled using nucleotides in the surrounding using nucleotides in the surrounding medium that are complementary to medium that are complementary to the existing DNA chains.the existing DNA chains.

They are joined to the original They are joined to the original nucleotide chain by H bondsnucleotide chain by H bonds

This is why DNA has complimentary base This is why DNA has complimentary base pairs: for accurate DNA replicationpairs: for accurate DNA replication

OriginalOriginal Chain 1Chain 1 Chain 2Chain 2 A-TA-T A-A- T-T-

G-CG-C G-G- C-C- T-AT-A T-T- A-A-

G-CG-C G-G- C-C- C-GC-G C-C- G-G- A-TA-T A-A- T-T-

DNA polymerase attaches at many DNA polymerase attaches at many different spots on the DNA chains, it different spots on the DNA chains, it does not begin at one end and end at does not begin at one end and end at the other. the other.

This is for faster DNA replicationThis is for faster DNA replication In fruit flies replication is initiated In fruit flies replication is initiated

simultaneously at about 6,000 sitessimultaneously at about 6,000 sites

MutationsMutations Replication occurs with a high degree of Replication occurs with a high degree of

accuracy.accuracy. A change in the nucleotide sequence at A change in the nucleotide sequence at

even one location can have serious effectseven one location can have serious effects Proofreading and repair keeps error to 1 in Proofreading and repair keeps error to 1 in

a billion nucleotidesa billion nucleotides Enzymes proofread and repairEnzymes proofread and repair Errors may still occurErrors may still occur Errors can also be caused by a variety of Errors can also be caused by a variety of

agents, including chemicals and UV agents, including chemicals and UV exposureexposure

RNARNA

Like DNA, RNA is a nucleic acid, but Like DNA, RNA is a nucleic acid, but differs in its structurediffers in its structure

Sugar molecule is Sugar molecule is ribose ribose (in DNA it (in DNA it is Deoxyribose)is Deoxyribose)

Instead of thymine, RNA contains the Instead of thymine, RNA contains the nitrogen base nitrogen base uraciluracil

Uracil pairs with adenineUracil pairs with adenine One strandOne strand

3 different types of RNA3 different types of RNA Messenger RNA: carries genetic Messenger RNA: carries genetic

information from the DNA in the nucleus information from the DNA in the nucleus to the cytosolto the cytosol

Transfer RNA: binds to specific amino Transfer RNA: binds to specific amino acids to carry them to ribosomes. acids to carry them to ribosomes. NITROGEN BASES ARE COMPLIMENTARY NITROGEN BASES ARE COMPLIMENTARY TO NITROGEN BASES ON mRNATO NITROGEN BASES ON mRNA

Ribosomal RNA: joined by proteins. Makes Ribosomal RNA: joined by proteins. Makes up the ribosomes where proteins are up the ribosomes where proteins are mademade

Transcription: genetic information is Transcription: genetic information is copied from DNA to RNAcopied from DNA to RNA

RNA polymerase: synthesizes RNA copies RNA polymerase: synthesizes RNA copies of specific sequences of DNAof specific sequences of DNA

RNA polymerase binds to specific spots of RNA polymerase binds to specific spots of DNA called DNA called promoterspromoters

When polymerase binds to promoters, the When polymerase binds to promoters, the DNA molecule in that region separatesDNA molecule in that region separates

Only one of the separated DNA chains, Only one of the separated DNA chains, called the template, is used for called the template, is used for transcriptiontranscription

RNA polymerase adds RNA polymerase adds complementary RNA nucleotides to complementary RNA nucleotides to the newly forming RNA moleculethe newly forming RNA molecule

Transcription continues until the RNA Transcription continues until the RNA polymerase reaches a DNA region polymerase reaches a DNA region called the called the termination signaltermination signal

Translation- translating RNA codons Translation- translating RNA codons into amino acids (which will build a into amino acids (which will build a protein)protein)

DNA DNA RNA RNA amino acids amino acids proteinsproteins

Codons- segments of RNA that Codons- segments of RNA that contains 3 nucleotides (nitrogen contains 3 nucleotides (nitrogen bases). Codes for amino acids. bases). Codes for amino acids.

MutationsMutations

Substitution (Point mutation)- a Substitution (Point mutation)- a mutation that exchanges one base mutation that exchanges one base for another (switching an A to a G, for another (switching an A to a G, for example)for example)

Insertion- mutations in which extra Insertion- mutations in which extra base pairs are inserted into a new base pairs are inserted into a new place in the DNAplace in the DNA

Deletion- mutations in which a Deletion- mutations in which a section of DNA is lost, or deletedsection of DNA is lost, or deleted

Frameshift- since protein coding DNA Frameshift- since protein coding DNA is divided into codons, each of which is divided into codons, each of which code for a protein, insertions and code for a protein, insertions and deletions can alter a gene so that its deletions can alter a gene so that its message no longer codes for the message no longer codes for the correct amino acids and the correct correct amino acids and the correct protein is not produced. protein is not produced.