The process of protein synthesis

What are the two processes of protein synthesis?

Transcription and Translation

What is the Central Dogma?

One way flow of genetic information

DNA → mRNA → Protein

What is a transcription unit?

a stretch of DNA that codes for a polypeptide or RNA

what is RNA Polymerase?

• Seperates DNA Strands and transcribes mRNA

• mRNA elongates in the 5’ → 3’ direction

• Uracil replaces Thymine when paring to Adenine

• Attatches to promoter (start of gene) and stops at the terminator (end of gene)

mRNA elongates in the?

5’ → 3’ direction

RNA Polymerase attatches to a?

Promoter (start of a gene)

RNA Polymerase stops at?

Terminator (end of a gene)

Codon?

a sequence of Three Nucleotides

What are the 3 stages of Transcription and Translation?

1. Initiation

2. Elongation

3. Termination

In Prokaryotes the RNA Polymerase attatches to the?

directly binds to the promotor

In Eukaryotes what must happen before RNA Polymerase can attach to the Promoter?

Transcription Factors must recognize the TATA Box

The TATA Box is?

a DNA sequence (TATAAAA)

located upstream from the Promotor

During the Elongation phase in Transcription, RNA Polymerase adds?

RNA Polymerase adds RNA nucleotides in the 5’ → 3’ direction.

Adding nucleotides to the 3’ end

What happens when RNA Polymerase moves during the Elongation phase in Transcription?

it untwists the DNA, then rewinds it after the mRNA is made

What happens during the Termination phase in Transcription?

RNA Polymerase transcribes a terminator sequence in DNA

The mRNA and RNA Polymerase detach

Termination phase in Prokaryotes during Transcription?

mRNA is ready t

Termination phase in Eukaryotes during Transcription?

pre-mRNA is ready

Why must pre-mRNA be modified in eurkaryotes?

So it can leave through the nuclear pores without getting broken down on its way to the ribosome

and is able to attach itself to the ribosome during translation.

what are the modifications made to the pre-mRNA?

• A 5’ cap is added (a modified guanine nucleotide)

• A 3’ poly-A tail

Pre-mRNA also has?

introns and exons

Introns are?

introns are non-coding sequences

Exons are?

Exons are codes for amino acids

when splicing occurs?

• Introns are removed to allow exons to join together.

• Exons join together to make a complete sequence.

Translation occurs in the?

Cytoplasm of the cell

Transcription occurs in the?

Nucleus of the cell

what are the 3 components of translation?

• mRNA

• tRNA

• Ribosome

mRNA

• messenger RNA

• the messenger which brings the DNA code to the ribosome in the form of RNA

tRNA

• transfer RNA

• Interprets the mRNA code at the ribosome to create amino acid chains

• Amino acid chains → polypeptides → proteins

Ribosome

• site of translation

• made up of 2 subunits

What are the 2 subunits of the ribosome?

• Top end of ribosome (large ribosomal subunit)

• Bottem end of ribosome (small ribosomal subunit)

What are the 3 active sites of the Ribosome?

• A Site

• P Site

• E Site

A Site

tRNA with new AA to be added

P Site

tRNA that holds growing polypeptide chain

E Site

exit site for tRNA

Initiation stage of Transation can be broken down into?

3 stages

i) Initiation

Small ribosomal subunit bind to Start codon (AUG) on the mRNA

ii) Initiation

tRNA carrying the correct anticodon (UAC) and amino acid (Met) attaches to the P Site

iii) Initiation

The Large ribosomal subunit attaches to the already formed structure

Elongation stage of Transation can be broken down into?

4 stages

i) Elongation

Codon Recognition

• tRNA anticodon matches codon in A Site

ii) Elongation

Peptide Bond Formation

• AA in A Site forms bond with peptide in P Site

iii) Elongation

Translocation

• tRNA in A Site moves to P site.

• P Site moves to E Site and tRNA with no amino acid exits

iv) Elongation

This process repeats until the entire polypeptide chain is complete

Translation - Termination can be broken down into?

3 stages

i) Termination

Once a stop codon is reached, translation stops

ii) Termination

A Release Factor binds to the stop codon and the polypeptide is released

iii) Termination

Ribosomal subunits dissociate

A single mRNA can be?

translated by several ribosomes at the same time