1. On the ribosome, the mRNA is read from _____ is a series of three nucleotides
ID: 96868 • Letter: 1
Question
1. On the ribosome, the mRNA is read from _____ is a series of three nucleotides called _____.
a. 5' to 3' ... codons
b. 3' to 5' ... anticodons
c. 3' to 5' ... codons
d.5' to 3' ... anticodons
2. Which of the following features of eukaryotic ribosomes in translation initiation is FALSE?
a. It uses an initiator tRNA that carries a methionine
b. It binds to the 5' end of the mRNA and moves forward to find the start codon
c. The large subunit of the ribosome is important for binding to the mRNA.
d. The large and small subunits of the ribosome combine once the initiation complex recognizes the AUG start codon
3.What evidence supports an RNA World?
a. RNA molecules can function as enzymes and are called ribozymes
b. DNA must be transcribed to RNA.
c. RNA is double stranded.
d. RNA is an intermediate product.
Explanation / Answer
So, the correct option is a) i.e. 5’ to 3’ and codon.
2. During eukaryotic translation, the first tRNA carries methionine (in bacteria it carries formyl methionine). The eukaryotic ribosome scans the mRNA from the 5’ direction for the start codon (AUG). During initiation, the large ribosomal subunit is bound after the small subunit is already bound to charged initiator tRNA, mRNA and many initiation factors and the complex has recognized the start codon. Hence all the statements are correct.
The primary function of the large subunit is NOT in the binding of mRNA, because mRNA is bound to the small subunit with the help of different initiation factors and only after the start codon of mRNA has been recognized by the small subunit complexed with the charged initiator tRNA and transcriptional factors, the large subunit gets bound. The major function of large subunit lies in its peptidyl transferase catalytic activity.
So, the statement c) is false. (Option c is correct because we are supposed to find the false statement)
3. As per the concept of RNA world, the earliest life forms had RNA as the genetic material. The evidence for this lies in the fact that RNA can catalyze reactions like the enzymes (and are called as ribozymes). Many RNA molecules can catalyze their own splicing. Similarly the peptidyl transferase activity of the ribosomal large subunit is associated with its rRNA component. The earliest life forms are expected to have simpler metabolic activities, so it cannot be expected that one type of molecule acted as genetic material (DNA) and other type of molecules (proteins) were used for the replication and processing. On the other hand it is more likely , that only type of molecule (RNA) was used as genetic material and the same molecule (RNA)catalyzed its own replication and processing.
So, the correct option is a)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.