AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

DNA MAKES RNA MAKES PROTEIN

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

A certain gene codes for a polypeptide that is 120 amino acids long. Approximately how many nucleotides long is the mRNA that codes for this polypeptide likely to be?

A	360
B	480
C	40
D	30

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: -Thus, a polypeptide having 50 amino acids shall be specified by a linear sequence of 150 nucleotides.

Detailed explanation-4: -Three is the minimum number of nucleotides per codon needed to encode 20 amino acids.

Detailed explanation-5: -Answer and Explanation: Given-The given protein contains 300 amino acids. Thus, the total number of nucleotides in the gene is 900.

There is 1 question to complete.