PROTEIN PROTEIN SYNTHESISSYNTHESIS

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DNA ReplicationDNA Replication

Occurs when chromosomes duplicateOccurs when chromosomes duplicate

An exact copy of the DNA is producedAn exact copy of the DNA is produced

Hydrogen bonds between bases break Hydrogen bonds between bases break and the molecule “unzips” with and the molecule “unzips” with helicaseshelicases

Each old strand of nucleotides serves Each old strand of nucleotides serves as a template for each new strandas a template for each new strand

New nucleotides move into position New nucleotides move into position according to Base Pair Rules with DNA according to Base Pair Rules with DNA polymerasepolymerase

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DNA DNA ReplicationReplication

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Why does DNA replicate?

Where does DNA replicate?

When does DNA replicate?

Protein Protein SynthesisSynthesis::

The process of The process of producing proteinsproducing proteins

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Making Proteins!Making Proteins! DNA carries the instructions for producing proteins

Proteins are made of amino acids linked together

20 different amino acids exist

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Why proteins?!?

• Antibodies, enzymes and hormones

• Hair, nails, muscles, skin

Where do the amino acids come from??

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Proteins are made by Ribosomes!

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RNA• RNA: Single strand that carries genetic info from the DNA to the ribosomes!

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RNA Differs from RNA Differs from DNA:DNA:

1.1. Sugar = RiboseSugar = Ribose

2.2. RNA contains the base Uracil (U)RNA contains the base Uracil (U)

in place of Thymine (T)in place of Thymine (T)

3.3. Single-strandedSingle-stranded

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DNA/RNA Building Analogy

• DNA is the official Master plan!• RNA is the cheap, disposable blueprint of the master plan

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The Base PairsThe Base Pairs

In RNA: A always pairs with U C always pairs with G

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Types of RNATypes of RNA

• Messenger RNA (mRNA)Messenger RNA (mRNA) carries carries message from DNA to the message from DNA to the ribosomesribosomes

• Transfer RNA (tRNA)Transfer RNA (tRNA) acts like a acts like a tow truck…taking amino acids to tow truck…taking amino acids to the ribosomethe ribosome

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The Genetic Code Genetic language reads 3 letters at a time

CODON: three consecutive nucleotides that specify a single amino acid.

U C G C A C G G U

is read as

UCG-CAC-GGU

which codes for

Serine-Histidine-Glycine

15There are 64 combinations!

Amino Acid Wheel

Use the code by reading from the center to

the outside

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Example: AUG codes for Methionine

Name the Amino Acids!

• GGG?• UCA?• CAU?

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Special Codons

• Some codons are called the “Start Codons” or “Stop Codons”

– These do not code for an amino acid

– They just indicate the beginning and end of a protein!

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Protein Synthesis1)Transcription2)Translation

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1) Transcription

Transferring info from DNA to mRNA The DNA strand separates & one strand acts as a template for RNA.

-Using rules of base pairs-Remember U instead of T!

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2) Translation

• The message in the mRNA is converted into proteins in the ribosome

• The information is being TRANSLATED!

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During Translation:

1) mRNA goes to ribosome2) Ribosomes read each codon one

at a time3) tRNA brings supplies for amino

acid3) Long chains of amino acids

make proteins!

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Making a ProteinMaking a Protein

DNADNA

mRNAmRNA

tRNAtRNA

ProteinProtein23

DNA DNA RNA RNA ProteinProtein

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Nuclearmembrane

TranscriptionTranscription

RNA ProcessingRNA Processing

TranslationTranslation

DNA

mRNA

mRNA

Ribosome

Protein

Eukaryotic Eukaryotic CellCell

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TranscriptioTranscriptionn

TranslatioTranslationn

(Single Strand)

Question:Question:

What would be the What would be the complementary RNA complementary RNA strand for the strand for the

following DNA sequence?following DNA sequence?

DNA = DNA = G C G T A T GG C G T A T G RNA = RNA =

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Question:Question:

What would be the What would be the complementary RNA strand complementary RNA strand for the following DNA for the following DNA

sequence?sequence?

DNA = DNA = G C G T A T GG C G T A T G RNA = RNA = C G C A U A CC G C A U A C

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mRNA carries the mRNA carries the info!info!

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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

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

Mutation: Changes in genetic material

• Like all mistakes, mutations can vary in shape & size!– Some mutations are neutral!– Some mutations are beneficial!– Some mutations are fatal!

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Mutations can occur naturally or be caused by environmental factors, such as:

-X rays -Drugs-Chemical exposure -UV light

-Tobacco smoke

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• Point Mutations: Involve changes in one nucleotide and usually don’t cause major problems.

-Substitution of one base

• Frameshift Mutations: When an entire nucleotide is added or deleted, all of the following codons are shifted.– This may change every single amino acid which

would greatly affect the protein

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Example of Point Mutation

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Example of Frameshift Mutation

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• Mutations in sex cells can be passed down to offspring and be good or bad!– Can cause major problems– May become new genetic variation in a species!

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