Skip to content
Login Register

#SYBR Green

2 public questions tagged with this topic.

PCR Modifications

What is the primary function of SYBR Green in qPCR?

SYBR Green I is a sensitive double-stranded DNA intercalating dye widely used in real-time PCR. In free solution its fluorescence is minimal, but upon binding to minor groove and intercalation between base pairs of duplex DNA, conformational restriction greatly enhances quantum yield, producing strong green emission under excitation. Signal intensity increases proportionally with amplicon accumulation, allowing quantification without sequence-specific probes. It does not block nonspecific amplification, cleave DNA or quench fluorescence; rather, it serves as reporter of total double-stranded product. Specificity must be confirmed by melt curve analysis since any duplex, including dimers, will fluoresce.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details
PCR Modifications

Which molecule does not distinguish between different DNA sequences in qPCR?

SYBR Green is an asymmetrical cyanine dye that intercalates into the minor groove of any double-stranded DNA without sequence recognition. Fluorescence increases over thousand-fold upon binding, providing signal proportional to total double-stranded product accumulation. In contrast, TaqMan, molecular beacons and Scorpion probes rely on complementary hybridization of oligonucleotide sequences containing fluorophore and quencher, thus discriminating specific amplicons from nonspecific products. Melting curve analysis is required with SYBR Green to verify product identity, as primer-dimers and off-target amplicons also generate fluorescence. Hence it reports amplification but lacks inherent sequence discrimination.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details