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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.
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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 purple protein in flowers Makes a white 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. DNA DNA • 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 RNA
Where does it happen? • Each gene has a promoter • Transcription factors help RNA polymerase bind to the promoter and begin transcription
Example – promoter=TATAA RNA polymerase AGCTATAACGACG T TAGCATCA T CGATAT T GCT GCAATCGTAGT T CGATAT T GCT GCAATCGTAGT DNA 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 GAC RNA UAC CGU CUG Protein Tyr ArgLeu
How? • A tRNA molecule carries an amino acid • tRNA nucleotides must be complementary to mRNA code
Beginning and End • Translation always begins at the Start Codon AUG and ends when a STOP codonis reached • Ex. RNA GTCA AUG GCC CCA UGG • Protein Met – Ala - Pro
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