AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

STRUCTURE OF NUCLEIC ACIDS

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

A certain gene in a bacterium codes for a polypeptide that is 120 amino acids long. How many nucleotides are needed in the mRNA to code for this polypeptide?

A	30
B	40
C	360
D	480

Explanation:

Detailed explanation-1: -Answer and Explanation: The correct answer is a. 360 nucleotides and 120 codons. Since each codon specifies one amino acid, the number of codons is equal to the number of amino acids.

Detailed explanation-2: -This is known as a codon. The codons of the mRNA are read and translated to produce a polypeptide. If 3 nucleotides (a codon) code for 1 amino acid, then the number of nucleotides required for coding 100 amino acids = 100 * 3 = 300.

Detailed explanation-3: -The mRNA is 336 nucleotides long, includes initiator and terminator codon. The number of amino acids in the polypeptide translated from this mRNA is 111.

Detailed explanation-4: -Thus, a polypeptide having 50 amino acids shall be specified by a linear sequence of 150 nucleotides. Therefore, option d) is correct. Q.

There is 1 question to complete.