6.1.5 Gene Control: Post-Transcriptional Modification Flashcards
What are the two types of sequences of DNA in eukaryotic genes?
Within eukaryotic genes, there are both coding and non-coding sequences of DNA
What are the coding sequences?
The coding sequences are called exons and these are the sequences that will eventually be translated into the amino acids that will form the final polypeptide
What are the non-coding sequences?
The non-coding sequences are called introns and are not translated (they do not code for any amino acids)
When are both exons and introns transcribed and what does this mean for the mRNA formed?
When transcription of a gene occurs, both the exons and introns are transcribed
This means the messenger RNA (mRNA) molecule formed also contains exons and introns
This RNA molecule is often referred to as primary mRNA or pre-mRNA
As the introns are not to be translated what happens?
As the introns are not to be translated, they must be removed from the pre-mRNA molecule
What happens to the exons after the introns are removed and what is the process called?
The exons are then all fused together to form a continuous mRNA molecule called mature mRNA that is ready to be translated
This process is sometimes called ‘splicing’ and is part of the process of post-transcriptional modification (referring to the modification of the RNA molecule after transcription but before translation occurs)
Splicing ensures that only the coding sections of mRNA are used to form proteins by translation (if any introns were included in the mature mRNA, the resulting protein would not be formed properly and may not function as it should)
What happens to polypeptides after they are formed by translation?
After polypeptides are formed by translation, they undergo modifications in the Golgi apparatus or in the cytosol
What happens to some polypeptides after they are formed by translation?
Some polypeptides may then require activation by cyclic AMP (also known as cAMP)
cAMP is derived from ATP and is formed by the action of the enzyme adenyl cyclase
Outline an important role carried out by cAMP.
Some polypeptides may then require activation by cyclic AMP (also known as cAMP)
cAMP is derived from ATP and is formed by the action of the enzyme adenyl cyclase
For example, when muscle cells require energy, an enzyme called glycogen phosphorylase releases glucose from glycogen
This enzyme is activated by cAMP, which changes the shape of the enzyme to expose its active site
