Problem 7 - Biology Concepts and Applications

Question

_____ different codons constitute the genetic code. a. 3 b. 20 c. 64 d. 120

Step-by-Step Solution

Answer

c. 64

Step 1: Understand the Genetic Code

The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins by living cells. It involves a sequence of three nucleotides, called codons, each of which specifies a particular amino acid or a stop signal.

Step 2: Determine the Number of Possible Codons

Since each codon consists of a sequence of three nucleotides and there are 4 different nucleotides (A, U, C, G) in RNA, the number of possible codons is calculated using the formula for permutations with repetition: \[ 4^3 = 4 \times 4 \times 4 = 64 \]This means there are 64 different codon combinations possible.

Step 3: Recognize the Answer

Based on the calculation, we know that the number of different codons is 64. Therefore, the correct answer is option 'c', which corresponds to 64.

Key Concepts

Codons

Codons are fundamental units of the genetic code in living organisms. When a cell synthesizes proteins, it reads the genetic instructions contained in its DNA or RNA.
These instructions are conveyed in the form of triplets known as codons.

• Each codon is a sequence of three nucleotides.
• There are 4 nucleotides (A, U, C, G) in RNA, resulting in a total of 64 possible codon combinations calculated as \(4^3 = 64\).
• A single codon corresponds to one amino acid or serves as a stop signal during protein synthesis.

The accuracy of these codons is vital to making sure proteins are synthesized correctly, as even a small mistake in the sequence can lead to disorders or diseases.

Nucleotides

Nucleotides are the building blocks of nucleic acids, such as DNA and RNA, which store and transmit genetic information.
They are composed of three components: a nitrogenous base, a sugar, and a phosphate group.

• In DNA, the nucleotides have the bases adenine (A), thymine (T), cytosine (C), and guanine (G).
• In RNA, thymine is replaced by uracil (U), so the bases are adenine (A), uracil (U), cytosine (C), and guanine (G).

Nucleotides play crucial roles in cellular processes, not only as the basic units of genetic material but also as molecules like ATP, which is essential for energy transfer.
When arranged sequentially in sets of three, these nucleotides form the codons that encode for proteins.

Amino Acids

Amino acids are organic compounds that serve as the building blocks for proteins, which perform a multitude of functions in living organisms.
Proteins are composed of long chains of amino acids, arranged in specific sequences as dictated by the genetic code.

• There are 20 standard amino acids in the genetic code.
• The sequence of these amino acids dictates the structure and function of a protein.

Codons (triplets of nucleotides) in the genetic code determine the specification of amino acids during protein synthesis.
For example, the codon AUG corresponds to the amino acid methionine, which also serves as the start signal for protein synthesis.
Thus, the genetic code ensures that each codon uniquely directs the inclusion of a specific amino acid in the growing protein chain.