ssDNA vs dsDNA

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

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BOTANY	BIOCHEMISTRY	MOL. BIOLOGY
ZOOLOGY	MICROBIOLOGY	BIOSTATISTICS
ECOLOGY	IMMUNOLOGY	BIOTECHNOLOGY
GENETICS	EMBRYOLOGY	PHYSIOLOGY
EVOLUTION	BIOPHYSICS	BIOINFORMATICS

Difference between dsDNA vs  ssDNA

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

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NOTES	QUESTION BANK	COMPETITIVE EXAMS.
PPTs	UNIVERSITY EXAMS	DIFFERENCE BETWEEN..
MCQs	PLUS ONE BIOLOGY	NEWS & JOBS
MOCK TESTS	PLUS TWO BIOLOGY	PRACTICAL

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