Question

The bacterium Mycobacterium tuberculosis has a single circular chromosome that is 4,410,000 base pairs (bp) in length. a. If the chromosome was stretched out linearly, how long would it be in micrometers? b. What is the diameter of the M. tuberculosis chromosome in micrometers? (Note: Circumference = πD, where D is the diameter of the circle). c. Suppose the M. tuberculosis genome is organized into loop domains with each loop domain contains 50,000 bp. If one of these loops was stretched out linearly, how long would it be in micrometers? d. How many histones are found attached to the M. tuberculosis chromosome?

Answer 1

Question (a).

Answer. Length of DNA = Length of 1 base pair X Number of base pairs.

= 0.34 nm X 4410000

= 1499400 nm

=1499.4 µm

Question (b)

Answer. Diameter of the circular DNA

Circumference of circular DNA = πD

Therefore , Diameter of the circular DNA = Cicumference/ π

= 1499.4 / 3.14

= 477.5 µm

Question (c)

Answer.

Length of the loop DNA when streched = 0.34 X 50000

= 17000 µm

Question (d)

Answer.

Number nucleosomes associated with M. tuberculosis chromosome= 4410000 / 200 [ Each nucleosome is 200 bp long]

= 2205 nucleosome.

As each nucleosome is associated with 8 histone proeteins.

Therefore , Number of Histones attached to the M. tuberculosis chromosome= 2205 X 8

= 17640.

Please feel free to ask , if anything is not understood.