Transcription and Translation

The Central Dogma of Biology

How does DNA make us who we are?

By making proteins! DNA contains the instructions for which proteins to make

*and complicated instructions on when to make them that we don’t fully understand

We Differ in our Protein Make Up

I.e. difference in pigments (hair, eye, skin etc.)

I.e. difference in enzymes (make different amounts of molecules)

I.e. difference in antibodies (some get sick more often or from different things)

*A lot of differences are also due to more complicated gene expression

Different Alleles Code for slightly

different versions of the protein

Probably arose through mistakes in DNA replication

Makes a white protein in flowers

Makes a purple protein in flowers

Transcription DNA-> mRNA Like making a copy

of the blueprint Kind of like DNA

replication- complementary nucleotides are added- EXCEPT U is used instead of T

RNA vs. D

NA

DNARNA

Deoxyribose sugar A,C, G and T nucleotides Usually double stranded Stores the code (like the

master blueprint) Ribose sugar A, C, G and U nucleotides Usually single stranded

› But can fold on itself Different types and functions

› mRNA, tRNA, rRNA› Carries code, assembles proteins

Accomplished by RNA polymerase

Where does it happen? Each gene has

a promoter Transcription

factors help RNA polymerase bind to the promoter and begin transcription

Example – promoter=TATAA

AGCTATAACGACG T TAGCATCAT CGATAT T GCT GCAATCGTAGTT CGATAT T GCT GCAATCGTAGT

DNARNA polymerase

GCUGCAAUCGUAGU

mRNA

Mr. Mahon’s Pet peeve

DNA is not turned into RNA!

An RNA molecule is made based of the DNA code!

Translation mRNA Protein in the ribosome

Basics of Translation Every 3 RNA nucleotides (letters) codes

for 1 amino acid› Called a “codon”

Example:DNA ATG GCA GACRNA UAC CGU CUGProtein Tyr Arg Leu

How? A tRNA molecule carries an amino acid tRNA nucleotides must be complementary

to mRNA code

tRNA (transfer RNA)

Codon Table

Beginning and End Translation always begins at the Start

Codon AUG and ends when a STOP codon is reached

Ex. RNA GTCA AUG GCC CCA UGG Protein Met – Ala - Pro

Translation Animation

Review Transcription

› DNA (gene) transcribed to make mRNA which carries code

› In Nucleus Translation

› mRNA code translated into a protein

› With help of tRNA in the ribosome