**Core Concept:**
The core concept of this question is about the concept of codons in the context of genetic code and translation in molecular biology. Codons are three-nucleotide sequences that specify amino acids in the genetic code.

**Why the Correct Answer is Right:**
The correct answer is **D** which states that there are 64 codons. This is because the genetic code consists of 64 possible combinations of three nucleotides (adenine, cytosine, guanine, and uracil), each representing an amino acid. This leads to the translation of mRNA into proteins.

**Why Each Wrong Option is Incorrect:**
Option A is incorrect because it states that there are 60 codons, which is incorrect considering the genetic code has 64 possible combinations. Option B mentions 62 codons, which is also incorrect as it does not account for the start and stop codons (AUG and UAA/UAG/UGA respectively) that are conserved in all three kingdoms of life (Archaea, Bacteria, Eukarya). Option C states 63 codons, which is also incorrect.

**Why Each Wrong Option is Incorrect:**
Option A states 60 codons, which is incorrect as it does not account for the start and stop codons. Option B mentions 62 codons, which is also incorrect as it does not account for the conserved start and stop codons across all three kingdoms of life. Option C states 63 codons, which is also incorrect as it does not account for the start and stop codons.

**Clinical Pearl / High-Yield Fact:**
Understanding the concept of codons and genetic code is essential in understanding molecular biology, particularly in the context of protein synthesis and translation in cells. This knowledge is crucial for medical students, as it helps them grasp the fundamental principles of genetic information processing and cellular processes.

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**Question:** What is the total number of codons?

**Answer:** Correct answer: D. There are 64 codons.

**Core Concept:** In molecular biology, codons are three-nucleotide sequences that represent amino acids during translation (the process of converting mRNA sequence into a protein). The genetic code consists of 64 possible codon combinations. These codons are responsible for specifying 20 amino acids, along with the start (AUG) and stop (UAA, UAG, UGA) codons.

**Why Each Wrong Option is Incorrect:**
A. 60 codons - This option is incorrect because it does not consider the start (AUG) and stop (UAA, UAG, UGA) codons.
B. 62 codons - This option is incorrect because it does not account for the start and stop codons.
C. 63 codons - This option is incorrect because it does not account for the start and stop codons.

**Clinical Application:** Understanding the genetic code and codons is crucial for medical students as it helps them comprehend molecular biology, protein synthesis, and the translation process in cells. This knowledge is essential for diagn