RNA & Protein SynthesisRNA & Protein Synthesis

Chapter 12-3Chapter 12-3

What is DNA used for?What is DNA used for?

DNA molecules are the coded instructions used DNA molecules are the coded instructions used by cells to build proteins (by cells to build proteins (Protein SynthesisProtein Synthesis)) Proteins are the keys to everything about a Proteins are the keys to everything about a

cell (looks, functions, growth, passing of cell (looks, functions, growth, passing of genetic information)genetic information)

Proteins are integral pieces of many cell Proteins are integral pieces of many cell structures (ex. Cell membrane) and perform structures (ex. Cell membrane) and perform many cell functions (regulating reactions, many cell functions (regulating reactions, transport, motion, protection, support, transport, motion, protection, support, communication)communication)

It is the presence of specific proteins that It is the presence of specific proteins that determines how an organism develops & determines how an organism develops & what characteristics an organism will havewhat characteristics an organism will have

What is DNA used for?What is DNA used for? Proteins are polymers made out of monomers Proteins are polymers made out of monomers

called amino acidscalled amino acids There are 20 different amino acidsThere are 20 different amino acids PolypeptidePolypeptide – a chain of amino acids – a chain of amino acids

Each protein contains a combination of any or all of Each protein contains a combination of any or all of the 20 different amino acidsthe 20 different amino acids

The properties of proteins are determined by the The properties of proteins are determined by the order in which the different amino acids are joinedorder in which the different amino acids are joined

In order to build a protein, cells must “know” which In order to build a protein, cells must “know” which amino acids to use & what order to put them inamino acids to use & what order to put them in

A DNA gene indicates which amino acids to use, A DNA gene indicates which amino acids to use, and what order to put them in, to build a specific and what order to put them in, to build a specific proteinprotein

What is DNA used for?What is DNA used for?

DNA molecules contain many individual DNA molecules contain many individual genes – each gene is the instructions to genes – each gene is the instructions to build one specific proteinbuild one specific protein

DNA only holds the instructions, it does DNA only holds the instructions, it does not actually do the building of proteinnot actually do the building of protein

RNA molecules carry out the process of RNA molecules carry out the process of making proteinsmaking proteins

Analogy - A dictionary is to Analogy - A dictionary is to words as DNA is to proteinswords as DNA is to proteins

In order to spell a word, you In order to spell a word, you must know which of the 26 must know which of the 26 letters to use and what order letters to use and what order to put them into put them in A dictionary holds this A dictionary holds this

informationinformation In order to build a protein, a In order to build a protein, a

cell must know which of the cell must know which of the 20 amino acids to use and 20 amino acids to use and what order to put them inwhat order to put them in DNA holds this informationDNA holds this information

The Structure of RNAThe Structure of RNA RNA (ribonucleic acid) is a long chain of RNA (ribonucleic acid) is a long chain of

nucleotidesnucleotides There are 3 main differences between There are 3 main differences between

DNA and RNA:DNA and RNA:

1.1. The sugar in RNA nucleotides is The sugar in RNA nucleotides is riboseribose

2.2. RNA molecules are RNA molecules are single-strandedsingle-stranded

3.3. RNA contains the base RNA contains the base uraciluracil (U)(U), but , but not thymine (T)not thymine (T)

Types of RNATypes of RNA

There are 3 main types of RNA:There are 3 main types of RNA:1.1. Messenger (mRNA)Messenger (mRNA) – an RNA copy of – an RNA copy of

a single gene that “carries” a single gene that “carries” instructions from DNA to ribosomeinstructions from DNA to ribosome

2.2. Ribosomal (rRNA)Ribosomal (rRNA) – makes up – makes up ribosome and assembles amino acids ribosome and assembles amino acids making a protein chainmaking a protein chain

3.3. Transfer (tRNA)Transfer (tRNA) – transfers amino – transfers amino acids from the cytoplasm to the acids from the cytoplasm to the ribosome for assemblyribosome for assembly

Protein SynthesisProtein Synthesis – How do cells – How do cells make protein?make protein?

Protein synthesis is a 2-step process:Protein synthesis is a 2-step process:

1.1. TranscriptionTranscription – an mRNA copy of a – an mRNA copy of a specific gene is madespecific gene is made

mRNA is a copy of a single gene, mRNA is a copy of a single gene, NOT an entire DNA moleculeNOT an entire DNA molecule

2.2. TranslationTranslation – information from mRNA – information from mRNA is used to build a proteinis used to build a protein

Building a protein is like building a Building a protein is like building a house…house… You need a master set of instructions for You need a master set of instructions for

the house in the construction office – this the house in the construction office – this is like the DNA in the nucleusis like the DNA in the nucleus

You need a work site to build the house – You need a work site to build the house – this is like the ribosomethis is like the ribosome

You need a copy of the master plan You need a copy of the master plan (blueprint) that can travel to the work site (blueprint) that can travel to the work site – this is like the mRNA– this is like the mRNA

You need workers to deliver the materials You need workers to deliver the materials to build the house to the job site – this is to build the house to the job site – this is like the tRNAlike the tRNA

You need builders to put all the materials You need builders to put all the materials together and make the house – this is like together and make the house – this is like the rRNAthe rRNA

Building a protein is like building a Building a protein is like building a house…house… The blueprint is copied and the copy is The blueprint is copied and the copy is

brought to the work site. Workers bring brought to the work site. Workers bring the correct materials to the work site and the correct materials to the work site and set them up according to the information set them up according to the information in the blueprint. Builders put everything in the blueprint. Builders put everything together building the house.together building the house.

An mRNA copy is made of DNA and the An mRNA copy is made of DNA and the mRNA travels to the ribosome. The tRNA mRNA travels to the ribosome. The tRNA brings the correct amino acids to the brings the correct amino acids to the ribosome and lines them up according to ribosome and lines them up according to the information in the mRNA. The rRNA the information in the mRNA. The rRNA puts the amino acids together forming the puts the amino acids together forming the protein.protein.

The Genetic CodeThe Genetic Code – How does an – How does an mRNA molecule “tell” a cell what mRNA molecule “tell” a cell what amino acids to use and where to amino acids to use and where to put them?put them? The mRNA instructions are called the The mRNA instructions are called the genetic genetic

codecode The genetic code is read 3 bases at a timeThe genetic code is read 3 bases at a time Each 3-base sequence is equivalent to 1 amino Each 3-base sequence is equivalent to 1 amino

acidacid CodonCodon – A 3-base sequence of mRNA that – A 3-base sequence of mRNA that

specifies a single amino acid in the protein specifies a single amino acid in the protein chainchain

A Triplet CodeA Triplet Code

The Genetic Code - ExampleThe Genetic Code - Example mRNA sequence UCGCACGGU has 3 mRNA sequence UCGCACGGU has 3

codons and is read like this: codons and is read like this: UCG – CAC – GGUUCG – CAC – GGU

Each codon stands for a specific amino Each codon stands for a specific amino acid acid UCG = serineUCG = serine CAC = histidineCAC = histidine GGU = glycineGGU = glycine

The polypeptide created from that mRNA The polypeptide created from that mRNA sequence would look like this:sequence would look like this: serine – histidine – glycineserine – histidine – glycine

TranscriptionTranscription – A closer look – A closer look In eukaryotic cells, transcription takes place In eukaryotic cells, transcription takes place

in the nucleus, in two steps:in the nucleus, in two steps:1.1. RNA polymerase “unzips” DNA at the RNA polymerase “unzips” DNA at the

correct locationcorrect location2.2. RNA polymerase uses one strand of DNA RNA polymerase uses one strand of DNA

to form a complementary mRNA moleculeto form a complementary mRNA molecule DNA:DNA: A G C G T G C C AA G C G T G C C A mRNA:mRNA: U C G C A C G G UU C G C A C G G U

mRNA can travel to a ribosome where the mRNA can travel to a ribosome where the protein can be assembledprotein can be assembled

Transcription is like finding the recipe you Transcription is like finding the recipe you want in a cookbook and copying it down want in a cookbook and copying it down onto a single sheet of paper – the copied onto a single sheet of paper – the copied recipe can then be brought to the kitchenrecipe can then be brought to the kitchen

TranscriptionTranscription – Animated – Animated MovieMovie

TranscriptionTranscription – 3D – 3D AnimationAnimation

TranslationTranslation – A closer look – A closer look Translation takes place on ribosomes and Translation takes place on ribosomes and

involves mRNA, rRNA, and tRNA moleculesinvolves mRNA, rRNA, and tRNA molecules tRNA is responsible for bringing the correct tRNA is responsible for bringing the correct

amino acids to the ribosomeamino acids to the ribosome tRNA molecules have amino acids bonded tRNA molecules have amino acids bonded

at one end, and three unpaired bases at one end, and three unpaired bases ((anticodonsanticodons) at the other) at the other

tRNA anticodons match up with tRNA anticodons match up with complementary mRNA codonscomplementary mRNA codons

Different tRNA molecules carry different Different tRNA molecules carry different amino acidsamino acids

TranslationTranslation – 5 Steps – 5 Steps1.1. mRNA attaches to ribosome – translation mRNA attaches to ribosome – translation

begins at AUG, the “start” codonbegins at AUG, the “start” codon2.2. Two complementary tRNA molecules carrying Two complementary tRNA molecules carrying

amino acids bond with the first two mRNA amino acids bond with the first two mRNA codonscodons

3.3. The ribosome bonds the amino acids together, The ribosome bonds the amino acids together, and breaks the bonds between the tRNA and breaks the bonds between the tRNA molecules an amino acidsmolecules an amino acids

4.4. The first tRNA is released and the ribosome The first tRNA is released and the ribosome moves down the mRNA to the 3moves down the mRNA to the 3rdrd codon, where codon, where another complementary tRNA brings in a 3another complementary tRNA brings in a 3rdrd amino acid which is bonded to the first twoamino acid which is bonded to the first two

5.5. The ribosome continues down the mRNA in this The ribosome continues down the mRNA in this way until a “stop” codon is reached and the way until a “stop” codon is reached and the finished protein is releasedfinished protein is released

Translation Translation – Animated – Animated MovieMovie

Translation – 3D AnimationTranslation – 3D Animation

TranscriptionTranscription – DNA – DNA “unzips”“unzips”

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – mRNA is – mRNA is mademade

TranscriptionTranscription – 3D – 3D AnimationAnimation

TranslationTranslation – ribosome – ribosome attaches to mRNA moleculeattaches to mRNA molecule

TranslationTranslation – translation – translation begins at AUG, the “start” begins at AUG, the “start” codoncodon

TranslationTranslation – tRNA anticodons – tRNA anticodons bond with complementary mRNA bond with complementary mRNA codonscodons

TranslationTranslation - 2 complementary tRNA - 2 complementary tRNA molecules carrying amino acids bond with molecules carrying amino acids bond with the first 2 mRNA codonsthe first 2 mRNA codons

TranslationTranslation – the ribosome bonds the 2 – the ribosome bonds the 2 amino acids together, breaks the bond amino acids together, breaks the bond between the first tRNA and its amino acid, between the first tRNA and its amino acid, and brings in a 3and brings in a 3rdrd tRNA tRNA

TranslationTranslation – the first tRNA is released, – the first tRNA is released, ribosome bonds the 2ribosome bonds the 2ndnd and 3 and 3rdrd amino acids amino acids together and breaks bond between 2together and breaks bond between 2ndnd tRNA tRNA and its amino acidand its amino acid

TranslationTranslation – ribosome moves – ribosome moves down the mRNA one codondown the mRNA one codon

TranslationTranslation – a 4 – a 4thth tRNA bonds with the 4 tRNA bonds with the 4thth mRNA codon, bringing in another amino acid mRNA codon, bringing in another amino acid to add to the growing polypeptide chainto add to the growing polypeptide chain

TranslationTranslation – the 2 – the 2ndnd tRNA is released, the tRNA is released, the33rdrd and 4 and 4thth amino acids are bonded together amino acids are bonded together

TranslationTranslation – ribosome moves – ribosome moves down the mRNA one codon down the mRNA one codon

TranslationTranslation – ribosome continues down the – ribosome continues down the mRNA in this way until a “stop” codon is mRNA in this way until a “stop” codon is reached and the finished protein is releasedreached and the finished protein is released

Translation – 3D AnimationTranslation – 3D Animation

Why is it important to eat Why is it important to eat protein?protein?

Your body needs 20 different amino Your body needs 20 different amino acids to make all the necessary proteinsacids to make all the necessary proteins

Your body is only able to produce 12 of Your body is only able to produce 12 of these amino acids on its ownthese amino acids on its own

The other 8 amino acids come from The other 8 amino acids come from foods you eat that contain protein foods you eat that contain protein (meat, nuts, dairy products, beans, etc.) (meat, nuts, dairy products, beans, etc.) – These are called – These are called essential amino acidsessential amino acids because you cannot survive without because you cannot survive without eating themeating them

The bottom line about DNA…The bottom line about DNA…

No DNA = No Protein = No Cells = No DNA = No Protein = No Cells = No LifeNo Life

Reproduction is all about passing Reproduction is all about passing DNA from one cell to another and DNA from one cell to another and from one generation of organisms to from one generation of organisms to the nextthe next

How To How To TranscribeTranscribe

DNA:DNA:

AA

TT

CC

GG

mRNA:mRNA:

UU

AA

GG

CC

How To Transcribe – How To Transcribe – Example 1Example 1

DNADNA:: TAC TCA CGC TAC TCA CGC ATCATC

mRNA:mRNA: AUG AGU GCG UAGAUG AGU GCG UAG

How to TranslateHow to Translate

Every 3 mRNA bases Every 3 mRNA bases together stand for 1 together stand for 1 amino acid in the amino acid in the protein chain – these protein chain – these pieces of mRNA are pieces of mRNA are called called codonscodons

Use the amino acid Use the amino acid chart to figure out chart to figure out which amino acid which amino acid each codon stands foreach codon stands for

How to Translate – Example 1How to Translate – Example 1

mRNA: AUG AGU GCG mRNA: AUG AGU GCG UAGUAG

AUG = Met (start codon)AUG = Met (start codon) AGU = SerAGU = Ser GCG = AlaGCG = Ala UAG = STOP UAG = STOP Protein: Met-Ser-Ala-STOPProtein: Met-Ser-Ala-STOP

Transcribe and Translate –Transcribe and Translate –Example 2Example 2

DNA : TAC TGA ATA CCT CAA GGA GGC ACC TGG DNA : TAC TGA ATA CCT CAA GGA GGC ACC TGG ACTACT

mRNA:mRNA: AUG ACU UAU GGA GUU CCU CCG UGG AUG ACU UAU GGA GUU CCU CCG UGG ACC UGAACC UGA

Protein: Met-Thr-Tyr-Gly-Val-Pro-Pro-Trp-Thr-StopProtein: Met-Thr-Tyr-Gly-Val-Pro-Pro-Trp-Thr-Stop

Transcribe and Translate –Transcribe and Translate –Example 3Example 3

DNA : TAC AAA GGA CGA GTA GTT TAA GCA AGA DNA : TAC AAA GGA CGA GTA GTT TAA GCA AGA ATTATT

mRNA:mRNA: AUG UUU CCU GCU CAU CAA AUU CGU UCU AUG UUU CCU GCU CAU CAA AUU CGU UCU UAAUAA

Protein: Met-Phe-Pro-Ala-His-Glu-Ile-Arg-Ser-StopProtein: Met-Phe-Pro-Ala-His-Glu-Ile-Arg-Ser-Stop