Protein Synthesis and Gene Expression zDNA: deoxyribonucleic acid--contains sugar deoxyribose. zDNA...

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Protein Synthesis and Gene Expression

DNA: deoxyribonucleic acid--contains sugar deoxyribose.

DNA is double stranded.

DNA contains bases adenine, thymine, guanine, cytosine.

DNA never leaves the nucleus.

RNA: ribonucleic acid--contains sugar ribose.

RNA is SINGLE stranded.

RNA contains bases adenine, guanine, cytosine and URACIL.

RNA can leave the nucleus.

Let’s Review DNA & RNA

Remember there are three types of RNA

mRNA: messenger RNAmRNA

tRNA towingAmino acid

rRNA: ribosomal RNA

tRNA: transfer RNA.

Overall process of protein synthesis

transcription translation

DNA RNA Protein

TRANSCRIPTIONTRANSCRIPTION

Takes place in the Takes place in the nucleusnucleus

translationtranslation

Moves out of nucleus Moves out of nucleus into the cytoplasm & into the cytoplasm & attach to ribosomeattach to ribosome

DNA’s tragedy

DNA contains volumes of information about making protein.

Unfortunately, DNA is too huge to leave the nucleus.

If I could onlyget out there…I’d show thema thing or two!

ribosomes

nucleus

How does the cell solve this problem….transcription

That’s where mRNA comes in.

mRNA helps get DNA’s message out to the ribosomes...

How do I tellthose guys what

I want them to do?

I can help!

First, DNA unzips itself...

DNA unzips itself, exposing free nitrogen bases.

Next, mRNA is made...

mRNA is made from the DNA template

mRNA matches with free DNA nitrogen bases in a complimentary fashion

mRNA leaves the nucleus...

DNA’s code is copied to mRNA in three letter groups called codons.

After mRNA is made from the DNA template, it is ready to leave the nucleus.

I hope he can tell them what

to do!

The next step...Translation

mRNA meets the Ribosomes!

(No, it’s not a new sitcom on Fox…)

mRNA tries to talk to the ribosomes…

mRNA leaves the nucleus and travels to the cytoplasm, where the ribosomes are located.

I have a message for you! It’sfrom DNA!

What does he want now?

It’s alwayssomething!Once there, mRNA

meets up with the ribosomes

mRNA tries to talk to the ribosomes…but is unsuccessful.

However, the ribosomes cannot understand the message mRNA is carrying.

Why don’t theyget it???@%$!!

Why can’t we tellwhat he’s saying?

We need a translator!

tRNA Saves the Day!

Now the cell can make a protein!

The boss will NOT be happy about

this...

We won’t work untilwe know what to do!

Where is thattranslator?

Looks like troublefor this cell…I’d better help!

Tyrosine

tRNA: Transfer RNA

Tyrosine Chemically, tRNA is clover-leaf shaped.

At one end, it carries an amino acid.

At the other end, it has a three letter code known as an anticodon.

Anticodon? What’s that?

This anticodon is the complement to the codons contained within mRNA.

Can you find the mRNA complement to the anticodon on tRNA?

Tyrosine

Some notes about Amino Acids

There are 20 known amino acids present in living things.

How is it possible to get a group of four letters to code for 20 things?

Put them into groups of three… 43 = 64 codes

Number of nitrogen bases

Number of members in a group of nitrogen bases

What’s a codon, anyway?

Here is what a codon looks like. It is a sequence of 3 bases.

How we determine what amino acid each codon codes for must be read off of a codon chart.

This is also known as the genetic code.

Codon chart

U C A G

UPhenylalaninePhenylalanineLeucineLeucine

SerineSerineSerineSerine

TyrosineTyrosineStopStop

CysteineCysteineStopTryptophan

C LeucineLeucineLeucineLeucine

ProlineProlineProlineProline

HistidineHistidineGlutamineGlutamine

ArginineArginineArginineArginine

A IsoleucineIsoleucineIsoleucineMethionine

ThreonineThreonineThreonineThreonine

AsparagineAsparagineLysineLysine

SerineSerineArginineArginine

GValineValineValineValine

AlanineAlanineAlanineAlanine

Aspartic AcidAspartic AcidGlutamic AcidGlutamic Acid

GlycineGlycineGlycineGlycine

First Base

Second Base

ThirdBase

The Wonderful World of Amino Acids

It is possible for some amino acids to have more than one codon.

There are three stop codons…they are UAA, UGA and UAG.

There is also one START codon…AUG.

How a Translator works…

First, the anticodons on tRNA meet up with the mRNA start codon (AUG) at the ribosome

Next, another tRNA meets up with it’s corresponding mRNA.

Each tRNA carries an amino acid.

Tyrosine

How a Translator works…

Once two amino acids are made, a bond forms between them

This process continues until a stop codon on mRNA is reached.

Tyrosine

Protein Synthesis and Gene Expression zDNA: deoxyribonucleic acid--contains sugar deoxyribose. zDNA...

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