Why DNA is negatively charged

What is DNA

Why DNA is negatively charged? Before coming to this answer let us discuss few important points related to this. Full form of DNA is deoxyribonucleic acid, it is a hereditary substance in humans and every kind of organisms. Almost all the cells in the body of a person contains similar DNA. DNA is important for all living organisms as it plays important role in inheritance, code proteins and most important is that it guide the genetic instruction for survival of life. Read also: Why do we need DNA ?

Deoxyribonucleic acid vs Ribonucleic acid

The three things that make up each strand of DNA and RNA are:

1. Nitrogenous Base (A,G,C,T)
2. Pentose sugar
3. Phosphate Group

1.Nitrogenous Bases

Bases are present in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). Bases are present in RNA are adenine (A), uracil (U), cytosine (C), and guanine (G).

As adenine pair with thymine A-T by two hydrogen bonds, therefore, takes less heat energy to denature. Guaninine pairs with cytosine G-C by three hydrogen bonds so takes more energy to break the bonds between them. Therefore, A-T base pair is more stable to heating than G-C base pair. Read: Complementary strands

Nitrogen bases in DNA are adenine, thymine, cytosine, and guanine. Adenine and guanine are purines. Thymine and cytosine are pyrimidines. The thymine nucleotide not present in RNA, it is replaced by uracil.

2. Pentose sugar

The 5-carbon sugars called as pentose sugars (pentose means five carbon atoms) are ribose (in RNA) and deoxyribose (in DNA). They are important components of nucleotides.

The DNA backbone is made of a repeated units of a sugar and a phosphate group. The sugar present in deoxyribonucleic acid (DNA) is called as deoxyribose. Therefore, DNA is called as deoxyribonucleic acid. Deoxyribose lacks an hydroxyl group at the 2′-position when compared to ribose. Therefore, it is called as deoxyribose.

RNA is not stable in alkaline conditions because of this hydroxyl group in 2nd position. Threfore, DNA is more stable because of deoxyribose sugar. Read: THYMINE and URACIL structure with diagram

The sugar present in the nucleotides makes RNA different from DNA. RNA molecule consists of ribose sugar, thus called as Ribonucleic acid.

Difference between thymine and uracil structure

3. Phosphate Group

DNA carries a negative charge because phosphate group present in DNA.

Nucleoside and Nucleotide

Nucleoside is defined as combination of a base and a sugar. Nucleotide is combination of a base, sugar and phosphate. Nucleotides are joined by phosphodiester bonds. Phosphodiester bonds are formed between hydroxyl and phosphate groups.

why DNA is negatively charged

Why DNA is negatively charged

DNA is negatively charged because of the phosphate group that forms sugar-phosphate backbone of DNA molecule. DNA carries a negative charge that dissolves in the water and thus it forms bonding with water. Therefore, DNA remains in the nuclear envelope and insoluble in negatively charged lipids.

Negative part of DNA is attracted towards the positive end of gel electrophoresis, and on applying electric current the movement of DNA will be from negative to positive electrode.

When DNA is released from the cell then it is soluble in water as the phosphate group of DNA carries a negative charge that dissolves in the water. Therefore, DNA always moves towards anode, which is positively charged.

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