DNA UnitDNA Unit

Structure of DNAStructure of DNA

- shape is a double helix- shape is a double helix

- a long polymer made of smaller - a long polymer made of smaller units (monomers) called units (monomers) called nucleotidesnucleotides

Structure of DNAStructure of DNA (cont) (cont)

- 4 different types of nucleotides- 4 different types of nucleotides

- Adenine (A)- Adenine (A)

- Guanine (G)- Guanine (G)

- Cytosine (C) - Cytosine (C)

- Thymine (T)- Thymine (T)

Structure of DNAStructure of DNA (cont) (cont)

- held together by hydrogen bonds- held together by hydrogen bonds

- pairing rules:- pairing rules:

A binds with TA binds with T

G binds with CG binds with C

Discovery of DNADiscovery of DNA

- model of shape proposed by - model of shape proposed by Watson and CrickWatson and Crick

- won Nobel Prize in 1962- won Nobel Prize in 1962

Discovery of DNADiscovery of DNA (cont) (cont)- Rosalind Franklin produced X ray - Rosalind Franklin produced X ray

photographs of DNAphotographs of DNA

- helped Watson and Crick develop - helped Watson and Crick develop their modeltheir model

- Did NOT win Nobel Prize for her work- Did NOT win Nobel Prize for her work

ReplicationReplication= the process of copying DNA= the process of copying DNA

- happens in the nucleus- happens in the nucleus

- DNA polymerases = enzymes that - DNA polymerases = enzymes that bond new nucleotides togetherbond new nucleotides together

ReplicationReplication

ReplicationReplication

ReplicationReplication

ReplicationReplication (cont) (cont)- result is two identical strands of DNA- result is two identical strands of DNA

- process has a proofreading system - process has a proofreading system to correct errorsto correct errors

ReplicationReplication (cont) (cont)- example:- example:

Replication Replication

TranscriptionTranscription= process of copying information from = process of copying information from

DNA to mRNA (messenger RNA)DNA to mRNA (messenger RNA)

- happens in the nucleus- happens in the nucleus

- RNA polymerases = enzymes that - RNA polymerases = enzymes that bond nucleotides to a mRNA strandbond nucleotides to a mRNA strand

TranscriptionTranscription (cont) (cont)- one side of the DNA (the template) is - one side of the DNA (the template) is

used used

- new rule: uracil (U) replaces thymine (T)- new rule: uracil (U) replaces thymine (T)

- U binds with A (but only in RNA)- U binds with A (but only in RNA)

TranscriptionTranscription

TranscriptionTranscription

TranscriptionTranscription

TranscriptionTranscription (cont) (cont)- example: - example:

(template)(template)

TranscriptionTranscription

(template)(template)

(mRNA)(mRNA)

TranslationTranslation= the process that converts info in = the process that converts info in

mRNA into proteinsmRNA into proteins

- done by ribosomes in the cytoplasm- done by ribosomes in the cytoplasm

- codon = 3 nucleotides together- codon = 3 nucleotides together

- each represents an amino acid- each represents an amino acid

TranslationTranslation (cont) (cont)- example: - example:

(mRNA)(mRNA)

Translation Translation

TranslationTranslation (cont) (cont)- example (cont): - example (cont):

mRNA strand broken into codonsmRNA strand broken into codons

Amino Acid Sequence = a proteinAmino Acid Sequence = a protein

Chart

TranslationTranslation (cont) (cont)- example (cont): - example (cont):

mRNA strand broken into codonsmRNA strand broken into codons

Amino Acid Sequence = a proteinAmino Acid Sequence = a protein

Chart

Central DogmaCentral Dogma

= the flow of information from DNA to = the flow of information from DNA to RNA to proteinsRNA to proteins

- involves the three main processes: - involves the three main processes: replicationreplication

transcriptiontranscription

translationtranslation

MutationsMutations

= a change in an organism’s DNA= a change in an organism’s DNA

- they can be neutral (do nothing), - they can be neutral (do nothing), harmful, or beneficial harmful, or beneficial

- a mutation may or may not effect the - a mutation may or may not effect the organismorganism

- depends on number of genes - depends on number of genes involved and location of mutationinvolved and location of mutation

Mutation Examples - NeutralMutation Examples - Neutral

mRNA sequence is AAGmRNA sequence is AAG

Codes for Amino Acid Codes for Amino Acid

mRNA sequence changes to AAAmRNA sequence changes to AAA

Codes for Amino AcidCodes for Amino Acid

Mutation did not effect the end outcome of Mutation did not effect the end outcome of what amino acid is producedwhat amino acid is produced

Chart

Mutation Examples - HarmfulMutation Examples - Harmful

Mutation Examples - BeneficialMutation Examples - Beneficial

Coronary Heart DiseaseCoronary Heart Disease

Blockage of the Coronary Artery supplying blood to the heart

Mutation helps protect people from blocked arteries

Mutation Examples - BeneficialMutation Examples - Beneficial

Sickle Cell DiseaseSickle Cell Disease

- homozygous recessive disease- homozygous recessive disease

- die if you get it- die if you get it

People who are heterozygous for People who are heterozygous for this disease don’t die of sickle cell this disease don’t die of sickle cell disease disease oror malaria malaria

MalariaMalaria

MutationsMutations (cont) (cont)

- mutations in body cells affect only - mutations in body cells affect only the organism itself and are not the organism itself and are not passed to offspringpassed to offspring

MutationsMutations (cont) (cont)

- mutations in sex cells (egg and - mutations in sex cells (egg and sperm) may be passed to offspringsperm) may be passed to offspring

- most of the time this is bad, but - most of the time this is bad, but not alwaysnot always

- another source of genetic - another source of genetic variation in organismsvariation in organisms

MutationsMutations (cont) (cont)

- mutagens = agents in the - mutagens = agents in the environment that can cause a environment that can cause a change in DNAchange in DNA

- ex: UV Light, industry chemicals- ex: UV Light, industry chemicalsRachel Carson – one of the first ecologist to warn against the widespread use of pesticides and other potential mutagens and toxins in her book Silent Spring in 1962. Her book helped launch the environmental movement.