4A- RNA and Protein Synthesis Flashcards
What is RNA?
A single polynucleotide strand that contains uracil instead of thymine.
What are the two types of RNA?
Messenger RNA (mRNA)
Transfer RNA (tRNA)
What is messenger RNA (mRNA)?
It’s made during transcription and carries genetic code from DNA to the ribosomes where it’s used to make a protein during translation.
It’s a single strand polynucleotide.
3 bases create a codon/bass triplet.
What is Transfer RNA (tRNA)?
It’s involved in translation.
Carries the amino acids to the ribosomes to create proteins.
It’s a single polynucleotide strand that is clover shaped. Held in shape by hydrogen bonds between base pairs.
It’s triplets are called anticodons
It also has an amino acid binding site
What is the first stage of protein synthesis?
Translation
What happens in translation?
An mRNA is made from DNA.
In eukaryotes it occurs in the nucleus, in prokaryotes it’s in the cytoplasm.
RNA polymerase attaches to the double helix.
The hydrogen bonds between bases break, uncoiling the DNA and exposing the bases.
One strand is then used as a template.
RNA polymerase lines up free floating RNA nucleotides that are attracted to their complementary bases. (T is replaced by U)
These free bases are joined to the strand by RNA polymerase. The RNA polymerase then moves along the DNA, separating the strand.
The hydrogen bonds between the two strands of DNA form once this has passed.
When it reaches a stop signal in the DNA it detaches.
It then moves to the ribosomes in the cytoplasm.
What is pre mRNA?
mRNA in eukaryotes containing both introns and exons, which then need to be spliced to form mRNA
What is splicing?
Splicing means removing the introns and then joining the exons together, creating mRNA.
This takes place in the nucleus.
Prokaryotic mRNA does not need to be spliced.
What is the second stage of protein synthesis?
Translation
What is translation?
It occurs in the ribosome.
Amino acids are joined together to produce a polypeptide chain that follows the sequence of the triplets on the mRNA.
What happens in translation?
The mRNA attaches to a ribosome and tRNA carries amino acids to it.
ATP is required in order for the bond between the amino acid and tRNA molecule to form.
A tRNA with a complementary anticodon attaches itself to the mRNA by specific base pairings. This continues.
The two amino acids are joined by a peptide bond. As the tRNA moves away, the amino acid is left behind.
This occurs until there is a stop signal.
Once the polypeptide chain moves away form the ribosome translation is complete.
