Modification of mRNA Flashcards
What does the modification of mRNA mean? 3
- mRNA strand can produce more than 1 amino acid sequence
- Alternative mRNA strands are translated into proteins with slightly different primary and tertiary structures
- So one gene can code for more than one protein
What does the DNA sequence contain?
- Introns
- Exons
What are introns?
Sections of DNA that do not code for amino acids
What are exons?
Sections of DNA that do code for amino acids
List the stages from DNA strand to completed mRNA strand 3
- Transcription
- Splicing
- Alternative splicing
What is formed from transcription of mRNA?
Pre-mRNA
What is pre-mRNA?
mRNA strand containing both exons and introns
What occurs in splicing?
Introns removed and exons joined
What occurs in alternative splicing?
Removes certain exons to form different mRNA strands from the same gene with different combinations of exons
Does modification of mRNA occur in prokaryotes?
No - no introns/splicing in prokaryotes
How is mRNA modified in antibodies? 2
- Two exons in the gene for an antibody heavy chain code for anchoring an antibody to the B cell membrane
- For a secreted antibody these are removed from pre-mRNA
How is a molecule of mRNA produced? 5
- DNA unzips and one strand acts as a template
- Ribonucleotides pair up with complementary bases
- RNA polymerase joins ribonucleotides together to form pre-mRNA
- The mRNA has fewer bases than pre-mRNA
- As a result of removal of introns so it is made up of exons only
How can mRNA formation account for more proteins than there are genes? 5
- It was assumed that one gene makes one protein
- One gene can make more than one mRNA
- One gene can code for several proteins
- Due to removal of different exons
- Post transcriptional change
What are splicing and alternative splicing?
Post transcriptional changes
