Question

Which one of the following combinations is found in DNA? (1) Guanine and guanidine (2) Guanidine and cytosine (3) Guanine and cytosine (4) Adenine and guanidine

Short answer

Option (3): Guanine and cytosine

Step-by-step solution

Understanding the Question

The question asks which pair of the given molecules can be found in DNA. DNA is composed of nucleotides, and the nitrogenous bases in DNA include adenine, thymine, cytosine, and guanine.

Identify the Nitrogenous Bases in DNA

DNA contains four main nitrogenous bases:1. Adenine (A)2. Thymine (T)3. Cytosine (C)4. Guanine (G)

Analyze the Options

Examine each option to identify if both of the components are nitrogenous bases found in DNA.Option (1): Guanine and guanidine - Guanine is a nitrogenous base in DNA, but guanidine is not.Option (2): Guanidine and cytosine - Guanidine is not a nitrogenous base in DNA; cytosine is.Option (3): Guanine and cytosine - Both guanine and cytosine are nitrogenous bases found in DNA.Option (4): Adenine and guanidine - Adenine is a nitrogenous base in DNA, but guanidine is not.

Select the Correct Option

From the analysis, the correct option is option (3) since both guanine and cytosine are nitrogenous bases found in DNA.

Key concepts

nitrogenous bases

In the world of DNA, four key players make up the sequence of our genetic information. These players are known as nitrogenous bases. They are:

• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)

These bases pair up with each other in a specific way to form the rungs of the DNA ladder. Adenine always pairs with thymine, and cytosine always pairs with guanine. This pairing is crucial for the process of DNA replication and function. When DNA replicates, it creates a complementary strand by matching these nitrogenous bases. This ensures that the genetic information is accurately copied. There are also other molecules like guanidine, but it is not involved in the structure of DNA. Knowing the correct nitrogenous bases helps in identifying the accurate components of DNA.

DNA structure

DNA is often described as a 'double helix'. This means it looks like a twisted ladder. The sides of this ladder are made up of alternating sugar and phosphate groups. The rungs of the ladder are made of pairs of nitrogenous bases which are held together by hydrogen bonds. These specific pairings create the steps of the ladder. Thanks to this structure, DNA is very stable and can store a vast amount of information. Each rung of the ladder encodes instructions and information critical to the functions of living organisms. The double helix structure is not just random twisting; it's a smart design that ensures the molecule is compact enough to fit inside the nucleus of a cell while remaining accessible for important processes like replication and transcription. Understanding the double helix helps in grasping how genetic information is conserved and replicated faithfully.

nucleotide

A nucleotide is the basic unit of DNA. Each nucleotide consists of three parts:

• A phosphate group
• A sugar molecule (deoxyribose in DNA)
• One of the four nitrogenous bases (adenine, thymine, cytosine, or guanine)

These nucleotides are linked together to form a long chain, with the phosphate group of one nucleotide connecting to the sugar molecule of the next. This chain forms one side of the DNA double helix. The sequence of nitrogenous bases along a DNA strand is crucial because it encodes the genetic information. Just like letters form words and sentences in a book, the sequence of these bases forms genes and instructions needed for the growth, development, and functioning of an organism. Each gene in our DNA is a specific sequence of nucleotides that tells the cell how to make a unique protein. These proteins are vital for almost all functions in a living organism, from digestion to immune response.