1. If the primary transcript of a eukaryotic gene has 3 exons:
exon 1| intron 1 | exon 2| intron 2 | exon 3
a. What would the mature mRNA look like if all intron splice sites were functional?
b. What would the mature mRNA look like if the 5' splice site of intron 1 was blocked?
c. What effect would such a mutation likely have on the protein translated from the mRNA?
d. What does the branch point nucleotide normally do during splicing?
e. What additional processing must these transcripts undergo besides splicing before they are exported from the nucleus?
2. Why does the RNA polymerase complex in eukaryotes contain a histone acetylase?
3. What is the function of the 5'cap in eukaryotic mRNA?
4. Why is the genetic code degenerate?
5. In translation, the first AUG codon of a eukaryotic mRNA transcript is mutated by replacing the A with a C.
a. How does this affect the primary structure of the synthesized polypeptide?
b. In a frame shift mutation, one base is either added or deleted. How does this mutation change the function of the protein produced?
c. Why is a mutation in the third position of a codon often called a silent mutation?
6. Briefly, explain how the ribosome can distinguish the initiating AUG codon from the AUG codons that specify a polypeptide's internal Met residues in prokaryotes and eukaryotes.
7. What is the minimum number of tRNAs required to recognize all the codons for Threonine? Give the anticodon sequences of this tRNA and indicate which codon(s) each one recognizes.