Cycle Threshold

a bit of mathematics.

Inside the PCR machine a polymerase chain reaction starts. It simply doubles the nucleic materials by copying the viral DNA into twos.

( Chain mathematics are very popular. Remember the creator of Chess game asking the king only one grain per square but doubled each time.)

In cycle 1
the single stranded RNA is doubled into a DNA by a RTase.
( RNA to DNA is called reverse)

In cycle 2
This DNA is doubled into two by a polymerase and so on.

Each cycle doubles the previous number: two copies become four, four copies become eight, and so on.
…
Here is a mental math ?

When a report says: CT value for N gene is 26,

please calculate how many times that gene is multiplied into, before getting detected ?

Ans:
2^25 = 33554432 times.

So a CT 26 means the viral DNA has to be multiplied into 3.3 crores times and piled up to cut into the threshold of detection.
Cycle Threshold

Now calculate the number for CT 40.