Structure and properties of RNA? Flashcards
What is RNA made of?
Nucleic acid but has ribose instead of deoxyribose
Is RNA single or double stranded?
Single
What are the two parts to the RNA structure?
Hairpin
Stem
Are there hydrogen bonds in an RNA molecule?
Yes, at the stem between the two sides of the strand
What is transcription?
Making RNA from DNA
What is translation?
Making protein from RNA
Name the four types of RNA
mRNA
tRNA
rRNA
snRNA
What does mRNA do?
Messenger RNA
Encodes amino acid sequence of a polypeptide
What does tRNA do?
Transfer RNA
Brings amino acids to ribosomes during translation
What does rRNA do?
Ribosomal RNA
Makes up the ribosome
Organelle that translates the mRNA
What does snRNA do?
Small nuclear RNA
Forms protein complexes that process RNA
Eukaryotes only
What are the three parts of a protein-coding gene?
Promoter
Coding sequence
Terminator
What is the promoter?
A base-pair sequence that specifies where transcription begins
What is the coding sequence?
A base-pair sequence that includes coding information for the polypeptide chain specified by the gene
What is the terminator sequence?
A sequence that specifies the end of the mRNA transcript
What is pre-mRNA?
RNA made directly from the DNA
Contains introns
Requires splicing
Describe the stages of transcription
DNA helicase unwinds the DNA forming the replication fork.
RNA polymerase comes in using transcription factors and recognises the promoter to begin transcription
Pre-mRNA is made in a 5’ to 3’ direction
RNA released and DNA helix reforms as RNA polymerase moves along
When terminator is reached, RNA polymerase stops and full pre-mRNA transcript is released
How does prokaryotic and eukaryotic mRNA differ?
Prokaryotic mRNA is said to be colinear with the protein sequence
It requires no splicing
In eukaryotic cells, what is added to the 5’ end of mRNA?
A cap of modified GTP
This occurs at the beginning of transcription
A signal for ribosomes to bind to the mRNA
In eukaryotic cells, what is added to the 3’ end of mRNA
A poly(A) tail of 150 or more adenine nucleotides is added It is needed for stability of the mRNA
What are the stages to removing introns from pre-mRNA?
The intron loops out as snRNPs, snRNAs and proteins bind to form a spliceosome
The intron is excised and the exons spliced together
What happens if introns are left in the mRNA transcript?
They will be translated and a variant of the protein will be produced which may or may not be functional.
