Transcription: Flashcards
Why do genes play a key role in protein synthesis?
= nucleotide sequence of a gene encodes the primary structure of a polypeptide
Where does transcription take place?
nucleus
What is the general basis for transcription?
= base sequence of a gene- copied into complementary base sequence (Mrna)
= moves to the cytoplasm
What happens in the first stage of transcription?
= DNA helicase breaks hydrogen bonds between the 2 strands
= complementary RNA nucleotides move into place and form hydrogen bonds with the complementayr base pairs with exposed nucleotides on one of the DNA strands
What is the second stage for transcription?
= RNA polymerase catalyses the formation of phosphodiester bonds between the RNA nucleotides
= and detaches from the DNA
What is the base sequence of the pre-mRNA similar to?
= the other polynucleotide strands base sequence- sense strand
What is the polynucleotide strand the mRNA is complementary to?
= antisense template strand
What happens to the DNA molecule and RNA when the polymerase enzyme detaches?
= goes back to normal double helix structure
= mRNA moves out of the nucleus by nuclear pores
What is the third stage of translation?
= mRNA splicing
What are introns and exons?
= introns- non coding
= exons- coding gene
=
What does pre-mRNA contain?
= exons and introns that are removed by splicing
= introns are removed
= ends of exons connected
= converts pre-mrna into mrna
Why does splicing not take place in prokaryotes?
= introns are uncommon in prokaryotic cells
