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DNA is negatively charged due to the presence of phosphate groups in nucleotides.
- The negative bonds formed between oxygen and phosphorus atoms result in a negative phosphate backbone.
- In DNA structure, a phosphate group contains a negatively charged oxygen atom.
- This negatively charged oxygen atom is responsible for the negative charge of your entire DNA strand.
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Key Terms: DNA, Phosphate, Oxygen, Negative charge, Nucleotides, Genetic, Nucleosome, sugar molecules, Phosphorus, DNA strand
What is DNA?
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DNA was identified by a Swiss biologist Johannes Friedrich Miescher in 1869 when he was researching the structure of white blood cells.
- DNA stands for Deoxyribonucleic acid, made up of nucleotides
- It is a unique genetic material found in prokaryotic and eukaryotic organisms.
- It carries the instructions that tell your body how to develop traits and even pass them on to your children
- It is responsible for the synthesis of protein molecules present inside the nucleus of all organisms.
- In humans, DNA is approximately 2.2 m long and present in a highly coiled state inside the nucleus which is called a nucleosome.
- Histone proteins help to maintain the structure of DNA in the nucleosome.
DNA
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| DNA Polymerases | Gene and DNA | Molecular Basis of Inheritance |
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Structure of DNA
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Your body has an amazing instruction manual called DNA. It is the basic genetic material made up of nitrogenous bases, sugar molecules, and phosphate groups. The nitrogenous bases consist of
- Thymine(T)
- Adenine(A)
- Guanine(G)
- Cytosine(C).
DNA has a double-stranded helical-shaped structure in the form of twisted ladders coiled around each other.
- The backbone of DNA is made up of sugar and phosphate groups that help in forming helical structures.
- DNA has antiparallel strands having 10 base pairs in each strand with 3 three-dimensional structures called double helix.
- The nucleotides of each DNA strand are connected by Hydrogen bonds.
- A and T have double bonds between them, while cytosine and guanine have triple bonds between them.
Structure of DNA
Types of DNA
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There are mainly 3 different types of DNA. These are
- A-DNA: It displays a right-handed helix conformation. It is the dehydrated form of DNA in extreme conditions.
- B-DNA: It also displays a right-handed helix conformation.
- Z-DNA: It displays a left-handed helix conformation.
All organisms, including humans, have their genetic information stored in the form of B-DNA. This B-DNA has the characteristic right-handed double helical structure.
Functions of DNA
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The following are the functions of DNA
- Mutations: Introduce changes in the genetic code.
- Replication: Creates copies of DNA before cell division.
- Transcription: Converts DNA code into RNA instructions.
- Translation: Uses RNA to build proteins.
- Gene expression: DNA and its interactions govern gene expression and determine which traits are displayed.
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| Translation | Allele | Packaging of DNA |
| Recombinant DNA Technology | DNA Replication | DNA Fingerprinting |
Things to Remember
- Deoxyribonucleic acid (DNA) is a unique genetic material found in prokaryotic and eukaryotic organisms.
- It is responsible for the synthesis of protein molecules present inside the nucleus.
- DNA consists of nitrogenous bases, sugar molecules, and phosphate groups.
- Hydrogen bonds connect the nucleotides of each DNA strand.
- The charge of DNA is due to the presence of phosphate groups in nucleotides.
Sample Questions
Ques. How does negative charge in DNA help in Gel electrophoresis? (2 Marks)
Ans. In Gel electrophoresis DNA gets loaded in negatively charged cathode wells which gets attracted to the positive side (towards the anode) due to the negative charge of DNA which helps in the isolation of DNA fragments.
Ques. Which form of DNA is found in humans? (1 Mark)
Ans. B- DNA is found in humans who have right-handed double helical-shaped structures.
Ques. What are the roles of Phosphates in DNA? (1 Mark)
Ans. Phosphate groups in DNA help in the formation of stable linked bonds between nucleotides of DNA which form phosphodiester bonds in the DNA structure.
Ques. What is the charge in DNA? (1 Mark)
Ans. DNA is negatively charged due to the formation of phosphodiester bonds between adjacent nucleotides to form alternating sugar and phosphate groups in DNA.
Ques. Why is DNA called acidic in nature? (2 Marks)
Ans. The acidic in nature comes due to the phosphate group which is quite similar to phosphoric acid which easily loses protons and makes nucleic acid to be acidic in nature.
Ques. Why is it important for DNA to be charged? (1 Mark)
Ans. The charge of DNA helps in cell machinery and the structural fundamentals of interaction between DNA and transcription factors.
Ques. What is the PH of DNA? (1 Mark)
Ans. The optimal PH for DNA so that its structure would not get denaturation ranges from PH 5 to 9.
Ques. Why is DNA soluble in water? (2 Marks)
Ans. DNA is negatively charged and polar in nature due to the presence of a phosphate backbone. As we know like dissolves in like, the polar nature of water makes DNA dissolve in it.
Ques. Does DNA move to the cathode or anode? (1 Mark)
Ans. DNA has a negatively charged backbone so when it is placed in an electric field it moves towards a positively charged anode.
Ques. Why are DNA strands antiparallel in nature? (1 Mark)
Ans. DNA strands are complementary to each other and run in opposite directions due to the base pairing between complementary base pairs.
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| NCERT Solutions for Class 11 Biology | NCERT Class 11 Biology Book | Biology MCQs |
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