3 If 104 bp of DNA represents a linear length of 34 nm how l

3. If 10.4 bp of DNA represents a linear length of 3.4 nm, how long (in meters) would one copy of the human genome (~3 × 109 bp) be if all of the DNA was placed end to end in a linear fashion?

4. Calculate the number of times a recognition site for a 4 bp restriction endonuclease is likely to occur in the diploid human genome

5. If a PCR reaction starts out with 20 double-stranded DNA targets, how many specific PCR products could be formed after 35 cycles of denaturation, annealing and extension.

Solution

3. In DNA double helix structure, each helix contain 10.4 basepairs and length of each lelix is 3.4 nm. One base pair length is 0.32 nm approximately.

= 0.32 x 10-9 meters.

Haploid genome size is 3 x 10 9 bp.

So length of DNA is:

0.32 x 10-9 x 3 x 109

= 0.32 x 3

= 0.96 meters

= Approximately 1 meter

4. All DNA made with only 4 bases and recognised restriction site length is 4 bases. Then 4 ^4 = 256

So every 256 bases, one restriction site appeared.

The diploid human genome contain, 6 x 10 9 bases. So total no. Of restriction sites in human diploid genome are:

6x10^9 / 256 = 23437500 sites

5. 20 x 2^35