DNA & Protein Synthesis

Protein synthesis definition

Process by which proteins are made from amino acids

Stages of protein synthesis

Transcription and translation

Location of transcription

Nucleus

Location of translation

Ribosome in cytoplasm

Role of DNA in protein synthesis

Provides base sequence code

Role of mRNA

Carries genetic code from DNA to ribosome

Role of tRNA

Brings specific amino acids to ribosome

Role of ribosome

Site where polypeptide is assembled

mRNA structure

Long single-stranded molecule

mRNA base sequence

Complementary to DNA

Codon definition

Triplet of bases on mRNA

tRNA structure

Single strand folded into cloverleaf shape

Number of nucleotides in tRNA

About 80

Amino acid attachment site

On one end of tRNA

Anticodon definition

Triplet of bases on tRNA

Function of anticodon

Complementary to mRNA codon

Specificity of tRNA

Each tRNA carries one specific amino acid

Transcription definition

Synthesis of mRNA from DNA

First step of transcription

DNA hydrogen bonds break and strands separate

Enzyme that unwinds DNA

RNA polymerase

Template strand name

Antisense strand

Free nucleotide pairing

Complementary base pairing

Bond formed in transcription

Phosphodiester bond

Enzyme forming phosphodiester bonds

RNA polymerase

Stop signal in transcription

Stop codon

DNA exposure during transcription

Only about 12 bases exposed at a time

Purpose of limited exposure

Reduces DNA damage

Pre-mRNA definition

Initial RNA transcript in eukaryotes

RNA splicing definition

Removal of introns

Introns definition

Non-coding sections of RNA

Exons definition

Coding sections of RNA

Final mRNA composition

Exons only

mRNA exit route

Nuclear pore

Translation definition

Assembly of amino acids into polypeptide

First step of translation

mRNA attaches to ribosome

Amino acid source

Cytoplasm

tRNA binding to mRNA

Complementary base pairing

Number of tRNA molecules bound

Two at a time

Bond formed during translation

Peptide bond

Enzyme forming peptide bond

Ribosome

Fate of tRNA after bonding

Detaches and reused

End of translation signal

Stop codon

Rate of translation

Up to 15 amino acids per second

Polyribosome definition

Multiple ribosomes on one mRNA

Maximum ribosomes per mRNA

Up to 50

Advantage of polyribosomes

Many proteins made simultaneously

Product of protein synthesis

Polypeptide chain