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Transcription, Translation & Gene Regulation
Follow information from DNA to RNA to protein. You will compare prokaryotic and eukaryotic processing, read the genetic code, and predict how operons, chromatin, and epigenetic marks turn genes on and off.
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What this chapter covers
- Transcription: Making RNA from DNA. MCAT questions ask you to read a template strand, name the polymerase, or compare bacteria with eukaryotes.
- Eukaryotic RNA Processing. Only eukaryotes process pre-mRNA, and the cap, tail, and spliceosome are all favorite MCAT targets.
- The Genetic Code, tRNA & Translation. You must read codons, name ribosome sites, and predict the effect of point mutations.
- Prokaryotic Gene Regulation: lac and trp Operons. Operon questions test whether you can tell inducible from repressible control and cis from trans effects.
- Eukaryotic Regulation & Epigenetics. Eukaryotes control genes at many levels, from chromatin packaging to mRNA stability, and heritable marks are now a core MCAT topic.
Key points to know
- RNA is made 5'→3' from the template read 3'→5'
- Pol II makes mRNA; pol I large rRNA; pol III tRNA and 5S rRNA
- 5' cap = 7-methylguanosine; poly-A tail added after the AAUAAA signal
- Spliceosome (snRNPs) removes introns and joins exons
- 61 sense codons, 3 stops (UAA, UAG, UGA); AUG = start
- Silent, missense, nonsense, frameshift: know the differences
- lac: inducible, OFF by default, allolactose releases the repressor
- trp: repressible, ON by default, tryptophan activates the repressor
Try a practice question
Which enzyme synthesizes mRNA in eukaryotic cells?
- RNA polymerase I
- RNA polymerase II
- RNA polymerase III
- DNA polymerase III
Show the answer
B. Pol II transcribes protein-coding genes into mRNA. Pol I makes large rRNAs and pol III makes tRNA and 5S rRNA. DNA polymerase III replicates bacterial DNA.
Common questions
What does this chapter cover?
Transcription, Translation & Gene Regulation covers Transcription: Making RNA from DNA, Eukaryotic RNA Processing, The Genetic Code, tRNA & Translation, Prokaryotic Gene Regulation: lac and trp Operons, Eukaryotic Regulation & Epigenetics.
What should I know first?
RNA is made 5'→3' from the template read 3'→5' Pol II makes mRNA; pol I large rRNA; pol III tRNA and 5S rRNA 5' cap = 7-methylguanosine; poly-A tail added after the AAUAAA signal
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.