Transcription Flashcards
why does DNA need a messenger
DNA is carried in the nuclues and is very long meaning it cannot exit through the nuclear pores. DNA uses mRNA in order to exit the nuclues.
what are five differences between DNA and mRNA
- RNA is made up of the sugar ribose
- Ribose is slightly different compared to deoxyribose
- mRNA is single-stranded. DNA is double-stranded.
- In mRNA thymine has been replaced by a slightly different nitrogenous base called uracil.
- mRNA is shorter than DNA
what is the process of transcription
Transcription is the process by which mRNA is made. Because RNA is single-stranded, transcription occurs on one of the two strands of DNA.
what is the template stand
The strand that is copied
what is the non template strand
the strand that is not copied
what is the non-template strand also referred to as?
the coding or the complementary strand
describe the steps of transcription
- A small section of DNA is unwound exposing the nucleotide bases
- RNA polymerase will attach to a promoter sequence
- It will run along attaching nucleotides from the nucleus
- The RNA polymerase will reach the terminator sequence where it will detach
- Once detached the DNA zips back up and coils itself into a helix
- Once the mRNA strand has been modified, packaged and completed it exits through the nuclear pore
what are the three modifications mRNA undergoes
- methylated cap
- poly-A tail
- splicing of introns
describe what a methylated cap is
Is a specially altered nucleotide that binds to the 5’ end of the RNA molecule. The cap acts as a signalling molecule that can be recognised by the ribosomes.
describe what a poly-A tail is
Is a sequence if adenine nucleotides are added to the 3’ end. Its function is to stabilize and protect the mRNA molecule.
describe what splicing is
Splicing is the process of removing the introns and joining the exons together.
what are transcription factors
Are special proteins that control which exons are spliced together
