Problem 13 - Biology: Concepts and Applications

Question

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

Step-by-Step Solution

Answer

64 different codons constitute the genetic code, corresponding to option c.

Step 1: Understanding Codons

A codon is a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule. Each codon corresponds to a specific amino acid or stop signal during protein synthesis.

Step 2: Calculating Possible Codons

There are four different nucleotides (adenine, cytosine, guanine, and uracil/thymine), and each codon is made up of three nucleotides. Therefore, the number of possible codons is calculated by raising the number of nucleotides to the power of the length of the codon: \[ 4^3 = 64 \] Thus, there are 64 possible codons.

Step 3: Selecting the Correct Answer

The choices given are 3, 20, 64, and 120. From the calculation, we determined that there are 64 different codons. Hence, the correct answer is option c. 64.

Key Concepts

Codons

In the world of genetics, a codon is a crucial concept that helps us understand how the DNA code translates into proteins. Codons are sequences of three nucleotides that work together to form a unit of genetic code found in DNA or RNA. The genetic code is like a language, using these sequences to instruct cells on how to construct proteins.
Each codon corresponds to a specific amino acid or sometimes acts as a stop signal during the process of protein synthesis.

• Amino acids are the building blocks of proteins.
• The sequence of codons ultimately determines the sequence of amino acids in a protein.
• Codons are essential for accurate protein production, ensuring the correct proteins are produced and function properly in the body.

Understanding codons allows scientists to decode the instructions within a DNA molecule and comprehend how genes are translated into the proteins that perform various functions within living organisms.

Nucleotides

Nucleotides are the basic building blocks of nucleic acids, such as DNA and RNA. These important molecules serve as the foundation upon which all genetic information is built. Each nucleotide is made up of three components:

• A phosphate group
• A sugar molecule (deoxyribose in DNA and ribose in RNA)
• A nitrogenous base (adenine, cytosine, guanine, thymine in DNA; uracil replaces thymine in RNA)

These nucleotides are connected in long chains to form the structure of DNA and RNA. The sequences of nucleotides in a DNA strand reflect the genetic instructions specific to an organism. When strung together, nucleotides form the codons that encode instructions for creating proteins. By understanding the role of nucleotides, we grasp how genetic information is stored, transmitted, and expressed within organisms.

Protein Synthesis

Protein synthesis is the biological process by which cells build proteins. It is an intricate system that involves reading codons and linking amino acids to form proteins vital for cell function and overall organism health. Protein synthesis occurs through two main steps: transcription and translation.

• Transcription: This is the first step where the genetic information in a DNA molecule is copied to a messenger RNA (mRNA) molecule. The mRNA serves as a temporary copy of the code that can be transported out of the nucleus.
• Translation: The mRNA is then read by ribosomes in the cytoplasm. Here, transfer RNA (tRNA) molecules bring the appropriate amino acids in accordance with the sequence of mRNA codons. The ribosome helps link these amino acids together, forming a polypeptide chain that will fold into a functional protein.

Understanding protein synthesis is critical because it explains how the instructions in our genes lead to the production of proteins, which are necessary for virtually every function and structure in an organism. By mastering these concepts, students can appreciate the complexity and efficiency of cellular processes at the molecular level.