RNA 2RNA 2TranslationTranslation

Big Picture

TraitProteinGeneDNA

4 basesBase paringDouble helix

Segment of DNA @ specific location.

Instructions for making

Proteins

Observed physical

Characteristics

Quick ReviewQuick Review

What does a protein do?

“Machinery” of the cell: pumps, enzymes, contraction, cytoskeleton...

Sure...but what are they?

Proteins are...Proteins are......polymers of amino acids

A “string of beads”

Amino acids have

1.Central carbon atom

2.Amino group

3.Acid Group

4.“Side Group”

There are 20 amino acids used in proteins, all with different “side groups.”

ProteinsProteins

Protein ChainsProtein Chains

The order and the properties of the amino acids of the 20 different types give proteins their unique characteristics and abilities.

It’s all about the code...

how do we get from a gene to a protein?how do we get from a gene to a protein?

We need a code that can tell us which amino acids to put where to get the results we want.

Genetic CodeGenetic CodeIt takes 3 DNA nucleotides to “code for” the 20 possible amino acids

1 molecule would give us how many options?

4 different bases in one location: A or T...

4 options or 41 (not enough)

2 molecules would give us...?

AA or AT or AG or...

16 options or 42 (not enough)

3 molecules gives us...?

64 options or 43 (plenty)

Using the 64 combinationsUsing the 64 combinations

One combination “starts” the sequence

DNA sequence: TAC

mRNA sequence: AUG

3 combinations “stop” the sequence

DNA sequences: ATT, ACT, ATC

mRNA sequences: UAA, UGA, UAG

Each 3-letter mRNA sequence is called a codon.

CodonsCodonsMore than one codon can code for an amino acid

Alanine = GCU, GCC, GCA, GCG

Each codon only codes for one amino acid.

GCU is always alanine

The redundancy, or back-up duplicates, in the code offer some protection from errors

Amino AcidsAmino AcidsPhenylalanine (Phe)Leucine (Leu)Isoleucine (Ile)Valine (Val)Serine (Ser)Proline (Pro)Threonine (Thr)Alanine (Ala)Tryosine (Tyr)Histidine (His)Glutamine (Gln)

Asparagine (Asn)Lysine (Lys)Glutamic Acid (Glu)Aspartic Acid (Asp)Cystenine (Cys)Tryptophan (Trp)Argenine (Arg)Glycine (Gly)

Methionine (Met)Start codon

CodonsCodonsCodons are like words

The letters tell you what the word means

Which amino acid to use

The words for a sentence

The combination of amino acids that produces the working protein.

How to we Read the Amino Acid (AA)

Chart?

How to we Read the Amino Acid (AA)

Chart?The chart is read by looking at the codon on the mRNA strand

Steps:

Read the mRNA codon and then look to chart to find the corresponding amino acid

Left,

Up,

Right

“Clockwise starting from

the left”

DNA Strand:•TACmRNA Strand:•AUGAmino Acid:•Met (Methionine)DNA Strand:•TACGTAAATmRNA Strand:•AUGCAUUUAAmino Acid:•[Met][Tyr][Leu]

How do we actually make proteins?

How do we actually make proteins?

TranslationTranslation

Transcription:mRNA Copy

Translation:Protein Synthesis

Proteins

Steps of Making Proteins

√

Making Proteins

• We already have:

• Protein making instructions (mRNA)

• We still need:

• A Workbench

• Amino Acids

Translation:Protein Synthesis

• To start the process, the mRNA is transported to a ribosome (workbench)

• In the ribosome, the mRNA will provide directions for how to make proteins

• This process is called translation

• Translation = the creation of proteins by linking chains of amino acids together (polymers)

• Occurs in cytoplasm or attached to RER.

mRNA to Proteins

The PlayersThe Players

• mRNA:

• messenger RNA

• tRNA:

• transfer RNA

• Ribosomes:*

• rRNA + Proteins

Transfer RNA: (tRNA)Transfer RNA: (tRNA)It’s job is to transfer amino acids from cytoplasm to ribosome1. Anticodon is located on the

bottom (base pairs to mRNA codon)

• Must match the mRNA codon exactly in order to pair

2. Amino acid attaches to the top

• The specific amino acid that the tRNA carries is determined by its anticodon

RibosomeRibosomeThe ribosome has two major parts (called subunits)

The large and small subunits

Both are made from proteins and ribosomal RNA (rRNA)

mRNA is pulled through and read only when the subunits join together

Disclaimer:You are not expected to know the exact details of Translation, but

it sometimes is helpful to see how the process works to better

understand it.

I will tell you what you should and should not know.

Disclaimer:You are not expected to know the exact details of Translation, but

it sometimes is helpful to see how the process works to better

understand it.

I will tell you what you should and should not know.

TranslationTranslation

Three parts

Initiation

Elongation

Termination

InitiationInitiation

1. Ribosome locks around the mRNA

2. tRNA pairs with start codon AUG,

•tRNA amino acid is Met (methionine)

ElongationElongation

• Codon Recognition, an incoming tRNA binds to the codon in right site

• Bond formation, the ribosome forms a bond between the new amino acid and the growing protein chain

Elongation ContinuedElongation Continuedthe tRNA in the right site is moved to the middle site, taking the mRNA along with it, middle site open to next tRNA

The tRNA in the right site moves to the left site and is released from the ribosome, the ribosome shifts the mRNA by one codon

TerminationTermination• When the ribosome reaches the termination codon

(UAG,UAA,UGA) on the mRNA

• The protein chain in released

• Subunits separate

PracticePractice

Turn to your neighbor...

Describe the summary of translation in your own words

Switch and have the other neighbor try it

Be Prepared to share your summary with the class

Translation Summary

Translation Summary

mRNA is sent from nucleus to cytoplasm

Ribosome attaches to the mRNA in the cytoplasm

tRNA’s bring the amino acids to the ribosome

It is the anticodon of the tRNA that determines which AA the tRNA carries

The first tRNA brings the AA Met to the start codon

Translation Summary

Translation Summary

The mRNA is read by the ribosome (pulled like a tape)

The mRNA codon is matched to the tRNA anticodon

If the codon & anticodon match, the AA is added to the protein chain

When the stop codon is reached on the mRNA, the ribosome separates and the protein is released

Put it all togetherPut it all together

Take out a half sheet of paper

Explain how a protein is made beginning from DNA

Be sure to include Transcription & Translation

This is a great level 3 question

PracticePractice

• Protein Synthesis

• Snorks