KELLY SPILLER MEDICAL MICROBIOLOGY EAST VIEW HIGH SCHOOL GEORGETOWN TEXAS Transcription and Translation

RNA vs. DNA DNA Double stranded Deoxyribose sugar Bases: C,G A,T RNA Single stranded Ribose sugar Bases: C,G,A,U Both contain a sugar, phosphate, and base.

Transcription Three steps  Initiation – DNA is unzipped and the RNA polymerase binds  Elongation – Gene is read and converted into complimentary RNA sequence  Termination – RNA polymerase detaches and the DNA zips back up

Initiation Initiation begins in the promoter region This is an area which signals the enzymes to attach and begin mRNA synthesis The transcription factor binds the DNA near the promoter region and signals the RNA polymerase to attach. RNA polymerase unzips the DNA on its own and begins to transcribe.

Elongation This process is similar to Replication however there is no Thymine in RNA. Uracil binds with Adenine instead. RNA polymerase also works on the 3’ to 5’ template strand creating mRNA that is oriented 5’ to 3’.

DNA polymerase RNA polymerase Read the 3’ to 5’ template strand Creates new 5’ to 3’ strand Requires a primer Requires helicase to unzip 1 error every 10 billion Read the 3’ to 5’ template strand Creates new 5’ to 3’ strand No primer required Unzips DNA without help Slower than DNA pol. (why?) 1 error every 10,000 nucleotides Why is proofreading less imp? DNA vs RNA Polymerase

Termination Termination occurs when the RNA polymerase reaches a “terminator” region. There are two type of termination.  Self termination – G/C rich sequence followed by A rich  Rho dependent termination – Rho protein stops it

Three Steps Translation also occurs in three steps:  Initiation  Elongation  Termination

Translation Ribosomes bind to the mRNA strand while it is still being elongated in transcription Ribosomes “read” 3 base sequences of mRNA called codons Translation begins at the AUG codon tRNA molecules with complimentary anticodon sequences bind, with the help of the ribosome, to their codon. tRNA molecules carry the specific amino acids coded for by the mRNA codon

Codon Chart

Transcribe Then Translate 5’CTAGATGCGTGATCTAG3’ 3’GATCTACGCACTAGATC5’ mRNA = A.A. =