Problem 52 - A Complete Resource Book in Chemistry for JEE Main

Question

A sequence of how many nucleotides in messenger RNA makes a codon for an amino acid? (a) one (b) two (c) three (d) four

Step-by-Step Solution

Answer

Three nucleotides make a codon in mRNA.

Step 1: Understanding Codons

In mRNA, a codon is a sequence that determines specific amino acids. Each codon is formed by a certain number of nucleotides. We need to recall the specific pairing and role that nucleotides play in this process.

Step 2: Exploring Nucleotide Grouping

The nucleotides in mRNA group into codons to code specific amino acids. This grouping uniquely determines the genetic information, so we must explore how the sequences are grouped to form these codons.

Step 3: Recalling Genetic Coding Rules

According to genetic rules, a codon is made up of a specific number of nucleotides in a sequence. Remember the rule: each codon in mRNA consists of a specific triplet of nucleotides, encoding one amino acid.

Step 4: Identifying the Correct Number

Given the options (one, two, three, four), we must choose based on our understanding of codons. The correct number of nucleotides per codon required for encoding amino acids is a key fact memorized in biology.

Key Concepts

Nucleotide Sequence

A nucleotide sequence in messenger RNA (mRNA) is a string of nucleotides, which are the building blocks of RNA. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. In mRNA, nucleotides line up in a specific order to encode information. The sequence of these nucleotides dictates the formation of codons, which are sets of three nucleotides each.

Nucleotide sequences are vital as they carry the genetic blueprints necessary for protein synthesis.

• Adenine (A)
• Cytosine (C)
• Guanine (G)
• Uracil (U)

These bases pair up in specific ways to ensure the accuracy of genetic coding. In DNA, adenine pairs with thymine, but in RNA, adenine pairs with uracil. Understanding the sequence helps us comprehend how genetic information is transcribed and translated into proteins. Knowing how these sequences are organized is crucial in studying genetic information.

Genetic Code

The genetic code is like a dictionary that translates nucleotide sequences into proteins. It consists of 64 codons, but only 61 codons correspond to amino acids, the building blocks of proteins. The remaining three are stop codons, which signal the end of protein synthesis.

In this code, each group of three nucleotides, or codon, corresponds to a specific amino acid. This triplet code implies that each amino acid is encoded by a sequence of three nucleotides. This concept can sometimes be tricky, but think of them as words made of three letters that represent an amino acid.

For instance:

• The codon AUG corresponds to the amino acid methionine.
• UGG codes for tryptophan.

The genetic code is universal, meaning it is nearly the same in almost all organisms, demonstrating the unity of life. Knowing the genetic code and how it translates nucleotide sequences into amino acids is fundamental for understanding genetic expression and mutation effects.

Amino Acids

Amino acids are organic compounds that combine to form proteins, which are essential for the body’s structure and function. There are 20 different amino acids that contribute to forming various proteins.

Each amino acid has a specific side chain, which is what gives it unique properties and functions. The sequence and number of amino acids determine the protein's shape and function.

Protein synthesis starts in the cell's nucleus, where mRNA transcribes genetic information from DNA. This mRNA then travels to the ribosome, where the codons are read, and amino acids are added in the right sequence to form proteins.

It is essential to understand how amino acids are linked together:

• The order of amino acids is determined by the codon sequence of the mRNA.
• Each triplet codon specifies which amino acid will be added next.
• Proteins are synthesized by linking amino acids in precise sequences to carry out specific functions.

Mastering how amino acids mimic the nucleotide trigger is key to unlocking the complexities of protein synthesis and overall cellular function.