regents biology chapter 8: from dna to protein section 8.4 - transcription

Regents Biology

Chapter 8: From DNA to ProteinSection 8.4 - Transcription

Regents Biology

What do we know so far? DNA

DNA is the genetic information Located in Nucleus (protected in vault)

Proteins all living things made of proteins Proteins made by ribosomes in cytoplasm proteins run living organisms

example – enzymes

So the DNA moleculeis the instructions

for making proteins!!!

I get it!!!

DNA is likea blueprint!!

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But there is a problem………. Need to get the blueprint information (DNA

message) from nucleus to cytoplasm

We need

a messenger

We need

mRNA!!!!

Regents Biologycytoplasm

nucleus

build proteins

DNA

RNA

Who is the mRNA messenger? messenger RNA

mRNA

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mRNA

The “Central Dogma” – information flows in one direction

DNA

transcription

cell nucleus cell cytoplasm

proteintranslation

trait(phenotype)

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You have to know differences between DNA and RNA for my test and EOC!!!!

DNA deoxyribose sugar nitrogen bases

G, C, A, T T = thymine

T : A C : G

double stranded

RNA ribose sugar nitrogen bases

G, C, A, U U = uracil

U : A C : G

single stranded

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Transcription is making mRNA from DNA

Double stranded DNA unzips by helicase enzyme

A G GGGGGT T A C A C T T T T TC C C CA A

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Now that DNA is unzipped; enzyme RNA polymerase attaches base pairs



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RNA polymerase will match RNA bases to DNA bases on one of the DNA strands

Notice NO THYMINE!!!!!!!

U


U

UU

U

U

G

G

A

A

A C CRNA

polymerase

C

C

C

C

C

G

G

G

G

A

A

A

AA


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U instead of T is matched to A in mRNA

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA


Once mRNA molecule is completed it leaves nucleus and goes to cell cytoplasm

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Chapter 8: From DNA to ProteinSection 8.5 - Translation

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nucleus

DNA instructions remain in nucleus

and we have to send message out

mRNA has the instructions for building

proteins from DNA

U C CCCCCA A U G U G A A A A AG G G GU U

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Proteins are built as chains of amino acids

What reads RNA? need a mRNA reader!

aa

aa

aa

aa

aa

aa

aa

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RNA to protein mRNA leaves nucleus mRNA goes to ribosomes in cytoplasm amino acids are linked bc of mRNA message proteins built from sequence of amino acids

aa aa aa aa aa aa aa aa

Now lets look at bigger picture!!!mRNA

U C CCCCCA A U G U G A A A A AG G G GU U

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aa

aa

aaaa

aa

aa

aa

mRNA

RNA to protein bigger picture

DNA

transcription

Cell nucleus

Cell cytoplasm

protein

translation

trait

U C CCCCCA A U G U G A A A A AG G G GU UribosomemRNA leaves

nucleus through nuclear pores

proteins synthesized by ribosomes using instructions on mRNA

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How does mRNA code for proteins?



protein

?

How can you code for 20 amino acids with only 4 nucleotide bases (A,U,G,C)?

think letters

in alphabet

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mRNA codes for proteins in triplets



Met Arg Val Asn Ala

Cys Alaprotein

Ribosomes read mRNA in blocks of 3 nucleotides called a “Codon”

codons

ribosome

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How are the codons matched to amino acids?



aminoacid

tRNA anti-codonUAC

Met

GCA

ArgCAU

Val

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Start codon AUG

Stop codons UGA, UAA, UAG

The mRNA code

codon formethionine (Met)

codon forleucine (Leu)

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aa

aa

aaaa

aa

aa

aa

mRNA

Summarize whole process of “DNA to Proteins”

DNA

transcription

Cell nucleus Cell cytoplasm

protein

translation

trait

U C CCCCCA A U G U G A A A A AG G G GU Uribosome

tRNA

aa

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proteinaa

aa

aa

aa

aa

aa

aa

aaaa

aa

aa

transcription

Cell cytoplasm

Cell nucleus

translation

trait

Different view of “DNA to Proteins”

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DNA

transcription

ribosome

tRNA

aminoacids

protein

translation

mRNA

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Section 8.6: Gene Expression and

Gene Regulation

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The BIG Questions… How are our traits turned “on”

or “off”?

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How do cells control Gene Expression? Cells turn genes “on” & “off” by controlling

transcription Remember what RNA Polymerase did?

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How do cells control Gene Expression?

For RNA Polymerase to do its job it has to attach to the DNA molecule

Promoter - area of DNA where RNA polymerase binds. Also area where the “Gene” sequence begins.

Operator – area of DNA that turns gene “on” or “off”. It’s the switch

Lets take a closer

look at how this

works!

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Gene regulation using “lac Operon Model”

The lac Operon uses a repressor protein as a stop sign until gene is ready to be made

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Do you want all your genes turned on if you just need to make one trait? NO!!!!!

Eukaryotic RNA is processed before leaving nucleus. “RNA Splicing”

Introns – gene segments that are cut out before mRNA leaves nucleus

Exons – gene segments that attach to each other that will code for mRNA

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http://www.pbslearningmedia.org/

resource/tdc02.sci.life.gen.proteinsynth/

from-dna-to-protein/

regents biology chapter 8: from dna to protein section 8.4 - transcription

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