3. If 10.4 bp of DNA represents a linear length of 3.4 nm, how long (in meters)

Question

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.

Explanation / Answer

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

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