Nucleic Acid and Genetic Code: Definition, Characteristics, Table, Facts, Properties

What are Nucleic Acids and Genetic Code?

Nucleic acids are giant molecules that are conclusively integral for all identified life forms, the most numerous being DNA, or deoxyribonucleic acid, and RNA, or ribonucleic acid. Nucleic acids are the molecules that bear the genetic information, the basis of such qualities as growth, development, and reproduction in living creatures. DNA stores the genetic code in its sequence. RNA reads the genetic code from DNA. This is called the process of transcription. Then, RNA carries the message to ribosomes. Ribosomes use this message in translation. In translation, the process of converting a gene to protein occurs. DNA to RNA to protein is the core flow. This is called the central dogma of molecular biology.

Types of Nucleic Acids

Nucleic acids are of two main types: DNA and RNA. Both are essential for storing and transferring genetic material and for protein synthesis. The types of nucleic acids are given below

DNA (Deoxyribonucleic Acid)

Structure of DNA:

DNA structure is a double helix. It is made up of two polynucleotide strands, which are made up of a phosphate group, a sugar molecule (deoxyribose), and a nitrogenous base.

Function of DNA:

DNA stores and transmits genetic information. It uses the genetic data required for the growth, operation, and reproduction in organisms, as well as many viruses.

Diagram: Double Helix Structure of DNA

RNA (Ribonucleic Acid)

Types of RNA (mRNA, tRNA, rRNA):

• mRNA (Messenger RNA): Carries the genetic code from DNA to the ribosome.

• tRNA (Transfer RNA): Brings amino acids during protein synthesis.

• rRNA (Ribosomal RNA): Structural and functional component of ribosomes.

Structure of RNA:

RNA is a more commonly single-stranded molecule. It is made of nucleotides comprising a phosphate group, a sugar molecule that is ribose, and a nitrogenous base.

Function of RNA:

RNA also has the function of synthesizing proteins. It is also involved in transferring genetic information in the form of DNA to proteins. It is involved in gene regulation and gene expression.

Diagram: Structure of Different RNA Types

Structure of Nucleic Acids

Nucleic acids like DNA and RNA are made up of repeating units called nucleotides, which are the basic building blocks. The structure of nucleic acids is listed below

Nucleotides: Building Blocks

Each nucleotide consists of three components:

1. Sugar: In nucleotides, the sugar can be deoxyribose, such as in DNA, or it can be ribose in RNA. Deoxyribose has one less oxygen than ribose, which makes the deoxyribose molecule more stable than the ribose molecule, and as a result, suitable for building the DNA molecule.

2. Phosphate: This group is formed by a P atom connected to four O atoms. This links the sugar molecules of two consecutive nucleotides, hence forming the framework of the nucleic acid polymer.

3. Nitrogenous base: Nitrogenous bases in nucleotides are of four types. In DNA, they are adenine (A), thymine (T), cytosine (C), and guanine (G). In RNA, instead of thymine, uracil (U) is used. These bases fit particularly (A with T/U and C with G) to code genetic information.

Diagram: Structure of a Nucleotide

DNA vs. RNA: Structural Differences

The Genetic Code

Genetic code is the instructions by which information contained in the DNA or RNA molecules is used to build a protein by cells of living organisms with the help of sets of three molecules of nucleotides known as codons. The genetic code is discussed below:

Characteristics of the Genetic Code

• Universality: Amazingly, the genetic code differs only in a very small percentage depending on the species. hence, it suggests that species have evolved from a single ancestor.
• Degeneracy: More than one codon may code for the same amino acid; this provides a defense against types of mutation.
• Nonoverlapping: This way, since each of the nucleotides in the sequence is part of only one codon, the genetic message is read in a sequential and nonoverlapping manner.

Codons and Anticodons

Codons are on the mRNA strand. Each codon codes for one amino acid. AUG is the start codon always. Ribosomes read codons during the process of translation. They form a chain of amino acids. Anticodons are found on tRNA. They match codons with base pairing. UAC pairs with the AUG codon. tRNA brings the correct amino acid. This helps in correct protein synthesis.

Diagram: Codon Table

Applications of Nucleic Acids

Nucleic acids have many important uses. They store and transfer genetic information. Their role goes beyond cell biology. They are used in modern science. Applications are seen in many fields:

Genetic Engineering

In genetic engineering, nucleic acids are employed in altering the DNA of living beings. Other methods, such as CRISPRCas9, enable scientists to bring genetic modifications for curing genetic diseases and improving crops for disease resistance.

Medical Diagnostics

In the diagnosis, nucleic acids are used for monitoring genetic diseases, infection, and the presence of cancer. Molecular methods like the PCR (Polymerase Chain Reaction) help to increase the amount of DNA and, hence, allow early and accurate identification of multiple diseases.

Biotechnology

Nucleic acids help make medicines. It is used in making vaccines and insulin. They support biofuel and GMO production. They help in eco-friendly product development. They are very useful in industrial biotech fields.

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MCQs on Nucleic Acids and Genetic Code

Question: Assertion: The genetic code is universal, meaning that the same codons specify the same amino acids in all living organisms.

Reason: The genetic code is determined by the specific sequence of nucleotides in DNA.

1. Both assertion and reason are true, and the reason is the correct explanation of the assertion.

2. Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

3. The assertion is true, but the reason is false.

4. The assertion is false, but the reason is true.

Answer: The genetic code is indeed universal, as the same codons specify the same amino acids in all living organisms. This is because the genetic code is determined by the specific sequence of nucleotides in DNA. The order of the nucleotides in DNA determines the sequence of nucleotides in mRNA, which in turn specifies the sequence of amino acids in a protein.

Hence, the correct answer is Option (1) Both assertion and reason are true, and the reason is the correct explanation of the assertion.

Question: What is not true for genetic code?

1. It is nearly universal

2. It is degenerate

3. It is unambiguous

4. A codon in mRNA is read in a non-contiguous fashion

Answer: DNA or mRNA sequences and amino acid sequences are connected through the genetic code, where each triplet of nucleotides, called a codon, encodes one of the 20 amino acids (e.g., glutamic acid, methionine, phenylalanine, serine, tryptophan, tyrosine, etc.). There are 64 codons in total, and the genetic code is read in a continuous and non-overlapping manner. The statement that codons are read in a "non-contiguous manner" is false, as codons are read sequentially without any spaces or interruptions between them. This continuous reading ensures that each codon is translated directly into an amino acid without any punctuation or gaps.

Hence, the correct answer is option 4) A codon in mRNA is read in a non-contiguous fashion

Question: Which of the following are the functions of RNA?

1. It is a carrier of genetic information from DNA to ribosomes synthesizing polypeptides.

2. It carries amino acids to ribosomes.

3. It is a constituent component of ribosomes.

4. All of the above.

Answer: RNA (ribonucleic acid) is crucial in cellular processes, particularly concerning protein synthesis and gene regulation. Its key functions encompass:

1. Messenger RNA (mRNA):
Role: It acts as a genetic courier from DNA in the nucleus to ribosomes in the cytoplasm for protein formation.
Mechanism: Transcription generates mRNA from DNA genes, which then serves as a blueprint for protein synthesis via translation.

2. Transfer RNA (tRNA):
Role: It is the amino acid taxi, delivering them to the ribosome during protein synthesis.
Mechanism: tRNA identifies mRNA codons using its anticodon, ensuring precise amino acid placement in the polypeptide chain.

3. Ribosomal RNA (rRNA):
Role: It is a fundamental component of ribosomes, the protein factories of the cell.
Mechanism: rRNA joins with proteins to create ribosomes, where it facilitates peptide bond creation between amino acids during translation.

Hence, the correct answer is option 4) All of the above.

Also Read:

• MCQs on Nucleic Acids—DNA and RNA

• MCQs on genetic code

• Properties of Genetic Material