GENEEXPRESSION

Transcription1. RNA polymerase unwinds DNA

2. RNA polymerase adds RNA nucleotides

(A ↔ U, G ↔ C)

3. mRNA is formed! DNA reforms a double helix

Transcription recap…

• RNA polymerase makes RNA using DNA sequence

• RNA leaves the nucleus for the cytoplasm

Translation

• Ribosomes translate mRNA into an amino acid sequence

• Amino acids form proteins

To a ribosome!

CodonsCodons = 3 nucleotides in a row

Ribosome recognizes a codon on mRNA and matches to the aniticodon on tRNA

A C G

anticodon

amino acid

tRNATransfer RNA transfers amino acids from the

cytoplasm to a ribosome

Anticodon = 3 nucleotides on one end of a tRNA

Anticodons base pair with complementary bases on mRNA

A C G

anticodon

amino acid

CodonsCodon triplets code for 1 of 20 amino acids

1 “start” codon 3 “stop” codonsCodons

Steps of Translation

1. mRNA attaches to ribosome

mRNA

Steps of Translation

2. tRNAs add amino acids based on how anticodons match to mRNA

mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

mRNA

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

2. tRNAs add amino acids based on how anticodons match to mRNA

Steps of Translation

3. Protein is released from ribosomes!

Protein chain

Stop codon

Steps of Translation

Protein chain

3. Protein is released from ribosomes!

SummaryDNA

RNA

PROTEIN

(Transcription)

(Translation)

Practice1.DNA sequence: AAC TGA CTG ATT GCA TGC• What is the complementary DNA sequence?• What is the complementary RNA sequence?

2.DNA sequence: TAG CAT TGG GCA TCA CGA• What is the complementary DNA sequence?• What is the complementary RNA sequence?

TTG ACT GAC TAA CGT ACG

UUG ACU GAC UAA CGU ACG

ATC GTA ACC CGT AGT GCT

AUC GUA ACC CGU AGU GCU

Determine the amino acids for this strand of mRNA:AUG GCA AGU UCU UGA

Practice

Met – Ala – Ser – Ser – STOP

Determine the amino acids for this strand of mRNA:UGU AGA GAU CUC UAA

Practice

Cys – Arg – Asp – Leu – STOP