BIOMOLECULES AND ENZYMES

BIOLOGY

PROTEINS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
In step 1 of translation, the ribosomal subunits, the ____, and the ____ carrying ____ bind together.
A
mRNA, tRNA, amino acid
B
sRNA, tRNA, methionine
C
DNA, tRNA, methionine
D
mRNA, tRNA, methionine
Explanation: 

Detailed explanation-1: -In both prokaryotes and eukaryotes the first step of the initiation stage is the binding of a specific initiator methionyl tRNA and the mRNA to the small ribosomal subunit. The large ribosomal subunit then joins the complex, forming a functional ribosome on which elongation of the polypeptide chain proceeds.

Detailed explanation-2: -Initiation ("beginning"): in this stage, the ribosome gets together with the mRNA and the first tRNA so translation can begin. Elongation ("middle"): in this stage, amino acids are brought to the ribosome by tRNAs and linked together to form a chain.

Detailed explanation-3: -First, three initiation factor proteins (known as IF1, IF2, and IF3) bind to the small subunit of the ribosome. This preinitiation complex and a methionine-carrying tRNA then bind to the mRNA, near the AUG start codon, forming the initiation complex.

Detailed explanation-4: -During initiation, the small ribosomal subunit binds to the start of the mRNA sequence. Then a transfer RNA (tRNA) molecule carrying the amino acid methionine binds to what is called the start codon of the mRNA sequence.

Detailed explanation-5: -During translation, ribosomal subunits assemble together like a sandwich on the strand of mRNA, where they proceed to attract tRNA molecules tethered to amino acids (circles). A long chain of amino acids emerges as the ribosome decodes the mRNA sequence into a polypeptide, or a new protein.

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