mr. armfield – level ii biology 1,2 science department deerfield high school, deerfield il...

Mr Armfield ndash Level II Biology 12Mr Armfield ndash Level II Biology 12Science DepartmentScience DepartmentDeerfield High School Deerfield ILDeerfield High School Deerfield IL

Transcription Translation ampTranscription Translation ampProtein SynthesisProtein Synthesis


Do you remember what proteinsDo you remember what proteinsare made of are made of

Hundreds of Amino Acids link together to make one Protein 1048708 There are 20 types of amino acids some we can make and some we canrsquot 1048708 There are infinite combinations of amino acids 1048708 Can be hundreds or thousands

monomersLongThese long chains are called polypeptide

chains


Protein SynthesisProtein Synthesis

Protein synthesis is the process in which a cell makes protein based on the message contained within its DNA

Howeverndash DNA is only found in the nucleusndash Proteins are only made outside the

nucleus ndash in the cytoplasm Houston we have a problem



How do the many different messages within the DNA molecule get to the many ribosomes outside the nucleus

A molecular cousin of DNA ndash RNA ndash is used to carry these messages


Ribonucleic Acids (RNA)Ribonucleic Acids (RNA)

The job of RNA (ribonucleic acid) is to carry messages from the DNA (in the nucleus) to the ribosomes (in the cytoplasm)

There are three types of RNA1 mRNA ndash carries a message from the DNA to

the cytoplasm2 tRNA ndash transports amino acids to the mRNA

to make a protein3 rRNA ndash make up ribosomes which make

protein



RNA is almost exactly like DNA exceptndash Contains a ribose sugar instead of a

deoxyribose sugar (hence the namehellip)

ndash Contains uracil instead of thyminendash RNA is single-stranded not double-

stranded (usuallyhellip)





Occurs in TWO steps1Transcription ndash the genetic

information from a strand of DNA is copied into a strand of mRNA

2Translation ndash the mRNA with the help of the ribosome forms a chain of amino acids (eventually forming a protein) based on the information contained on the mRNA


The Central DogmaThe Central Dogma

This order of events is called the central dogma of molecular biology

DNA RNA P RO T E

IN


Step One Step One TranscriptionTranscription

1 DNA unzips enzymes split apart base pairs and unwind the DNA double helix

2 Bases pair up Free nucleotides in the cell find their complementary bases along the new strands with the help of RNA polymerase What will be different

3 New backbone formed The sugar-phosphate backbone is assembled to complete the RNA strand and separates from the DNA strand



Watch this simplified animationhttpwwwstolafedupeoplegianniniflashanimatmolgeneticstranscriptionswf

Watch the more complex animation

httpwww-classunledubiochemgp2m_biologyanimationgenegene_a2html



Try it What RNA strand will be made from the following DNA sequence

TACGCATGACTAGCAAGTCTAACT




TACGCATGACTAGCAAGTCTAACTAUGCGUACUGAUCGUUCAGAUUGA


Step 1frac12 Step 1frac12 RNA EditingRNA Editing

An mRNA molecule has to be ldquoeditedrdquo in order to be useful Therersquos a lot of unnecessary information that needs to be removed

An mRNA sequence that does NOT code for protein is called an interoninteron A sequence that is useful in making a protein is called an exonexon



DNA

exon 1 interon exon 2 interon exon 3

pre-RNA (in nucleus)

exon 1 exon 2 exon 3

RNA (in cytoplasm)

transcription

interon

interon

RNA editing


Step Two Step Two Translation ldquoTranslation ldquoto decode ordecipher the meaning ofrdquo

Now that our mRNA molecule has been made itrsquos time for its message to be made into a protein sequence

How does the mRNA sequence translate into an amino acid sequence


Step Two Step Two TranslationTranslation

Problem ndash There are 20 different amino acidsndash There are 4 RNA bases

phe ile val pro ala his asn asp cys argleu met ser thr tyr gln lys glu trp gly

A T C G



Watch this simplified animationhttpwwwstolafedupeoplegianniniflashanimatmolgeneticstranslationswf





1 So how do you exactly go about determining what protein your cells are going to make

2 FIRST Divide the mRNA sequence into codons As you just saw and heard codons are three-base sections of mRNA

AUG|CGU|ACU|GAU|CGU|UCA|GAU|UGA



2 Since each 3-letter combination ldquocodesrdquo for an amino acid you need to figure out what amino acid matches up with each codon



The Genetic CodeThe Genetic Code




met







met


asp arg thr asp arg ser






met


asp STOPmet thr asp arg ser


RECAPRECAP

1 DNA is transcribed into mRNA in the nucleus

2 The mRNA leaves the nucleus and enters the cytoplasm

3 The protein is translated from the mRNA sequence using tRNA and amino acids


Do you remember what proteinsDo you remember what proteinsare made of are made of

Hundreds of Amino Acids link together to make one Protein 1048708 There are 20 types of amino acids some we can make and some we canrsquot 1048708 There are infinite combinations of amino acids 1048708 Can be hundreds or thousands

monomersLongThese long chains are called polypeptide

chains
















protein

















DNA RNA P RO T E

IN

























DNA




RNA (in cytoplasm)

transcription

interon

interon

RNA editing









A T C G




















met







met








met




RECAPRECAP



















protein

















DNA RNA P RO T E

IN

























DNA




RNA (in cytoplasm)

transcription

interon

interon

RNA editing









A T C G




















met







met








met




RECAPRECAP




















DNA RNA P RO T E

IN

























DNA




RNA (in cytoplasm)

transcription

interon

interon

RNA editing









A T C G




















met







met








met




RECAPRECAP




























DNA




RNA (in cytoplasm)

transcription

interon

interon

RNA editing









A T C G




















met







met








met




RECAPRECAP












A T C G




















met







met








met




RECAPRECAP























met







met








met




RECAPRECAP









met








met




RECAPRECAP









met




RECAPRECAP





RECAPRECAP




mr. armfield – level ii biology 1,2 science department deerfield high school, deerfield il...

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strand of dna

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molecular cousin of