Single Stranded DNA (ssDNA) vs Double Stranded DNA (dsDNA): Similarities and Differences


single stranded and double stranded DNA

ssDNA vs dsDNA – A Comparison Table

The DNA molecules are not always double stranded helical structures, sometimes they occur in single stranded form called ssDNA. In 1959 Robert Sinsheimer discovered a unique bacteriophage called φX 174 (which infect Escherichia coli) with single stranded DNA as its genetic material. Even though the chemical composition of single stranded and double stranded DNA are the same, they also show some characteristic differences. The present post describes the similarities and differences between dsDNA and ssDNA.s

Similarities between dsDNA and ssDNA

Ø  Both dsDNA and ssDNA can acts as genetic material

Ø  Both are polymers of nucleic acids

Ø  The sugar molecule in both the case is deoxyribose

Ø  Both contain purines and pyramidines

Ø  Both ssDNA and dsDNA contain the nitrogen bases A, G, T and C

Ø  Both can absorb UV light

Difference between dsDNA vs  ssDNA

Sl. No.dsDNAssDNA
1Double stranded DNA is linear or filamentous formSingle stranded DNA is usually stellate or star shaped
2Total number of adenine will be equal to total number of thymine. Similarly total number of guanine will be equal to the total number of cytosineNo such relationships in ssDNA
3A / T ratio is 1Adenine thymine ratio will be ~ 0.77
4G / C ratio is 1G / C ratio is 1.3
5dsDNA is more stablessDNA is less stable
6dsDNA is resistant to the action of formaldehydessDNA is highly susceptible to the action of formaldehyde, The amino groups of the bases of single stranded DNA readily react with formaldehyde
7The UV absorption of dsDNA increase from 0 to 80oCThe UV absorption of ssDNA increase from 20 to 90oC
8Double stranded DNA behaves as a rigid rod like structureSingle stranded DNA behaves as a randomly coiled polymer
9Present in almost all organismsPresent in very few viruses such as φX 174
10Follows Chargaff’s ruleDo not follows Chargaff’s rule
11Purine by pyrimidine ratio will be 1Purine by pyrimidine ratio varies greatly


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