Introduction to Molecular Biology 4 Flashcards
Leaning objectives
Explain the principles of the genetic (triplet) code and identify START and STOP codons.
Outline the process of RNA-protein translation.
List types of mutation and their consequences.
Define the role of Transfer RNAs and how they are ““charged”” with specific amino acids.
Give examples of post-translational modifications of proteins
Explain the processes by which proteins transported within and out of the cell
What is a codon?
a string of 3 nucleotides that eventually code into amino acids
What are the start and stop codons?
Start: AUG
Stop: T or UAG, T or UAA, T or UGA
What happens with insertions or deletions mutations.
Nonsense proteins are translated and the reading frame messes up, stop codons may be accidentally made
What happens with base substitution (missense) mutations
Stop codon may be made which is worst case scenario or another amino acid may be made.
What happens with silent mutations?
The third base may be switched but there is no change because the last amino acid changed may still code for the same amino acid
What is a polymorphism?
Minor change in DNA sequence that is present in less than 1% of the population
What are the non coding regions?
5’ methyl cap and 3’ poly A tail
What is t-RNA and what is its structure and function?
t-RNA is an RNA molecule with a clover like structure with a 3’ acceptor arm which binds to an amino acid. The most bottom clover leaf has the anticodon that bind with the m-RNA to check for the right m-RNA codon
What is aminoacyl t-RNA synthetase.?
An enzyme that attaches the appropriate amino acid onto its t-RNA. It is a very specific structure, one for each amino acid and has an editing for errors in t-RNA coding pairing
Describe the large and small ribosomal subunits
the small ribosomal subunit, on the bottom which reads the RNA, and the large subunit, on the top which joins amino acids to form a polypeptide chain.
Describe the binding sites
E-site: Exit site where
Describe the three steps of translation
Initiation: the 5’ cap structure is recognized by the cap binding protein complex which then recruits ribosomes. The ribosomes scan through the non coding regions until the initiation codon is found (requires initiation factors)
Elongation: Charged tRNA’s then bind to the codon and a peptide bond is made between the amino acids, amino acid chain continues to be made and elongated
Termination: Once stop codon is reached, the bond between the protein and last tRNA is broken to released finished protein and the whole complex disassociates. (requires termination factors
Describe the wobble phenomenon
When t-RNA binds with the m-RNA codon, it may not be 100% accurate, the last base pair is usually more relaxed and different t-rna may bind to it
What are polysomes?
Multiple instances of protein translation on the same m-RNA chain
