Gene ExpressionGene Expression

From genotype to From genotype to phenotypephenotype

From Gene to ProteinFrom Gene to Protein

DNAIn Genes

TranscriptionRNA is created

Translation

Amino Acids are sequenced into a protein.

Proteins are physical expression of gene =phenotype

A gene is a specific sequence of a DNA molecule that codes for a protein.

TRANSLATION

TRANSCRIPTION

RNA PROCESSING

Structure of RNAFormed from Formed from

nucleotide subunitsnucleotide subunitsSingled StrandedSingled StrandedUracil instead of Uracil instead of

ThymineThymineSugar is riboseSugar is ribose

Look familiar?Look familiar?

TranscriptionTranscription RNA polymeraseRNA polymerase pries the DNA strands pries the DNA strands

apart and hooks together the RNA apart and hooks together the RNA nucleotidesnucleotides

RNA synthesis follows the same base-RNA synthesis follows the same base-pairing rules as DNA, except uracil pairing rules as DNA, except uracil substitutes for thyminesubstitutes for thymine

Watch it in action!

Elongation

RNApolymerase

Nontemplatestrand of DNA

RNA nucleotides

3 end

Direction oftranscription(“downstream”) Template

strand of DNA

Newly madeRNA

3

5

5

Promoter Codon

Terminator Codon

Transcription produces three types Transcription produces three types of RNAof RNA

•Ribosomal RNA (brown) makes up ribosomes. rRNA•Messenger RNA (pink): provides template mRNA•Transfer RNA (green): transfers amino acids to ribosome tRNA

CodonsCodons Specific sequence of Specific sequence of

three nucleotides on three nucleotides on the mRNA.the mRNA.

Used to code for Used to code for amino acids.amino acids.

The Genetic Code The Genetic Code Chart is based on Chart is based on codons.codons.

TranslationTranslation

Changing from the language of Changing from the language of nucleotides, to the language of nucleotides, to the language of amino acids.amino acids.

Codon (mRNA)

UUUTranslation

Amino Acid

Phenylalanine

Codon sequence ties to specific Codon sequence ties to specific amino acidsamino acids

Second letterU C A G

Fir

st

lett

er

(5’

en

d)

U

C

A

G

Th

ird

lett

er

(3’

en

d)

UCAG

UCAG

UCAG

UCAG

= Stop Codon

= Start Codon

Translation happens Translation happens with the help of with the help of tRNAtRNA

Each tRNA has:Each tRNA has:– anti-codonanti-codon– Attached amino acidAttached amino acid

Example:Example:– Amino Acid: LeucineAmino Acid: Leucine– Codon (mRNA): CUUCodon (mRNA): CUU– Anti-codon (tRNA): GAAAnti-codon (tRNA): GAA Anti-

codon

Translation Stage 1: InitiationTranslation Stage 1: Initiation1.1. Small ribosomal subunit binds AUG Small ribosomal subunit binds AUG

sequencesequence• AUG codon signals start of sequenceAUG codon signals start of sequence• AUG codes for methionine (Met)AUG codes for methionine (Met)

2.2. Large subunit then bindsLarge subunit then binds

Translation Stage 2: ElongationTranslation Stage 2: Elongation

Watch it!

Translation Stage 3: TerminationTranslation Stage 3: Termination

Ribosome reaches a stop codon on Ribosome reaches a stop codon on mRNA.mRNA.

New protein is released from New protein is released from ribosome.ribosome.

Ribosome subunits disconnect.Ribosome subunits disconnect.

RNA splicing• Most eukaryotic genes and their RNA Most eukaryotic genes and their RNA

transcripts (mRNA) have long noncoding transcripts (mRNA) have long noncoding stretches of nucleotides that lie stretches of nucleotides that lie between coding regionsbetween coding regions

• Noncoding regions are called Noncoding regions are called intronsintrons• The other regions are called The other regions are called exonsexons

because they are because they are exexpressedpressed• translated into amino acid sequencestranslated into amino acid sequences

• RNA splicingRNA splicing removes introns and joins removes introns and joins exons (spliceosome)exons (spliceosome)• creating an mRNA molecule with a continuous creating an mRNA molecule with a continuous

coding sequencecoding sequence

RNA splicing

5 Exon Intron Exon Intron Exon 3Pre-mRNA

1 30 31 104 105 146

Codingsegment

Introns cut out andexons spliced together

1 1465Cap

5Cap

Poly-A tail

Poly-A tail

5 3UTR UTR

Exon = expressedIntron = spliced out

MutationsMutations– Base substitution mutationsBase substitution mutations– Base insertion or deletionsBase insertion or deletions

One or two nucleotide pairs are inserted into or One or two nucleotide pairs are inserted into or deleted from the moleculedeleted from the molecule

Frameshift mutationFrameshift mutation

MutationsMutations

The Jamba Juice AnalogyThe Jamba Juice AnalogyFor protein synthesisFor protein synthesis

ProductsProducts

Jamba Juice ProductJamba Juice Product

Various flavored Smoothies!Various flavored Smoothies!

Cell ProductCell Product

Various proteinsVarious proteins

Nucleus of the operation. Locked inside this building Nucleus of the operation. Locked inside this building are the recipes for all Jamba Juice smoothies.are the recipes for all Jamba Juice smoothies.

Recipes =Recipes = ???? Building = ??Building = ??

Jamba Juice Corporate Jamba Juice Corporate Headquarters, Emeryville, CAHeadquarters, Emeryville, CA

Transcribing the recipesTranscribing the recipes

mRNA

Jamba Juice StoresJamba Juice Stores

rRNA/ribosomes

Transport of materials to storesTransport of materials to stores

tRNA

Jamba Juice MixologistsJamba Juice Mixologists

Mixologists are the A and P sites in the ribosome –Translates recipe (codons) to fruit ingredients (amino acids)

Jamba Juice SmoothieJamba Juice Smoothie

Combines fruits (amino acids) into a smoothie (protein).