DNA replication Flashcards
What is the central dogma of molecular biology?
The flow of genetic information:
DNA → RNA → Protein
Transcription: DNA is copied into RNA.
Translation: RNA is used to synthesize proteins
What are the three stages of transcription?
Initiation – RNA polymerase binds to promoter.
Elongation – RNA strand is synthesized.
Termination – RNA synthesis stops
What enzyme is responsible for transcription?
RNA polymerase II (for mRNA in eukaryotes).
What is a promoter region?
A DNA sequence that signals RNA polymerase to start transcription.
What is the TATA box, and why is it important?
A sequence rich in A and T in the promoter.
Helps RNA polymerase and transcription factors bind.
What enzyme unwinds DNA during transcription?
Helicase – breaks hydrogen bonds to “unzip” the DNA strands.
What happens during elongation?
RNA polymerase moves along the template strand.
Inserts complementary RNA nucleotides (A, U, C, G).
Synthesizes RNA in the 5’ to 3’ direction.
What strand does RNA polymerase read, and in what direction?
Reads the template strand in the 3’ to 5’ direction.
Produces RNA complementary to this strand.
How does transcription end?
RNA polymerase reaches a termination signal.
RNA strand detaches from DNA.
What is topoisomerase, and why is it needed?
Prevents DNA from overwinding during transcription.
Cuts DNA to relieve tension, then reseals it.
How does RNA polymerase start transcription without a primer?
It has primase activity, meaning it can add nucleotides from scratch.
What are UTRs (Untranslated Regions)?
Sequences before and after the coding region in mRNA.
5’ UTR & 3’ UTR help with stability and translation regulation.
What happens to pre-mRNA before translation?
Splicing – removes introns (non-coding regions).
5’ Cap – adds a modified guanine at the start.
Poly-A Tail – adds a long chain of adenines to the end.
What is translation?
the process of converting mRNA into a protein using ribosomes.
Why is splicing important?
Removes introns (non-coding regions).
Joins exons (coding regions) to make mature mRNA.
