$DNA$ polymerase enzyme is responsible for the synthesis of

Okazaki fragments are formed:

If a hybrid $DNA$ $(^{14}N-^{15}N)$ is allowed to undergo replication twice in a medium containing nucleotides with $^{15}N$ base,then what proportion of light,heavy,and hybrid $DNA$ will be obtained respectively?

Replication of $DNA$ occurs in which direction?

Ten $E. coli$ cells with $^{15}N$-dsDNA are incubated in a medium containing $^{14}N$ nucleotides. After $60$ minutes, how many $E. coli$ cells will have $DNA$ totally free from $^{15}N$ (in $cells$)?

Which property of $DNA$ double helix led Watson and Crick to hypothesise semiconservative mode of $DNA$ replication? Explain.