2.3 Transcription (PS) Flashcards
What is transcription the process of?
Copying DNA into RNA
What is transcription the first stage of?
Protein synthesis
Why isn’t DNA used in protein synthesis?
It is too big to fit through nuclear pores, to leave the nucleus, go to the ribosomes, to make proteins
What is used instead of DNA in protein synthesis?
RNA
What does DNA helicase do in the process of transcription?
It unzips the DNA strand
What is the template strand?
The DNA strand used to make an MRNA copy (the antisense strand)
What does RNA polymerase do?
It lines up free nucleotide bases along side the template strand
What do the free RNA nucleotides do?
They begin complimentary base pairing with the template strand
What enzyme are nucleotides joined together by and what bonds form?
- RNA polymerase
- phosphodiester
What happens once the RNA polymerase has passed by a section of DNA?
It begins to recoil as hydrogen bonds reform
What happens when RNA polymerase reaches the stop codon?
It stops making preMRNA and detaches from the DNA
What other process occurs before the preMRNA can leave the nucleus?
Post transcriptional modification
What happens in post transcriptional modification?
- preMRNA contains introns and exons
- introns are removed by splicing
- exons are joined to make mRNA
What are exons?
Coding sequences in the preMRNA
What are introns?
Non coding sequences in preMRNA
They are unnecessary, as a result they are spliced out
