Biology, Eighth Edition (Raven)

Chapter 15: Genes and How They Work

Translation Initiation

What is the function of ribosomal RNA? Ribosomes are complex structures composed of both protein and RNA. About two thirds of the mass of a ribosome is RNA, making ribosomal RNA the most abundant type of RNA in the cell. Ribosomal RNA functions in binding mRNA and tRNA and then moving them precisely through the ribosome in order to add amino acids to a polypeptide chain. The small subunit of a ribosome contains a sequence of ribosomal RNA that binds mRNA at the beginning of translation. Without this binding site translation might not begin at the appropriate location on the mRNA.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

Which of the following is not involved in the initiation of translation?
A)mRNA
B)ribosomal subunits
C)initiator tRNA
D)RNA polymerase
E)all of the above are involved
2.

The Shine-Dalgarno sequence is found on the ________.
A)small ribosomal subunit
B)large ribosomal subunit
C)initiator tRNA
D)mRNA
E)IF3
3.

Which of the following binds to the initiation complex first?
A)IF2
B)IF3
C)initiator tRNA
D)large ribosomal subunit
4.

The initiation factors IF2 and IF3 use the energy of ATP to link the ribosomal subunits.
A)True
B)False
5.

If IF1 is not present, elongation would not occur.
A)True
B)False
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