Question

The DNA dependent DNA polymerases catalyse polymerisation only in one direction, that is ___(i)___. The replication is continuous on the template strand with polarity ___(ii)___ . Replication is discontinuous on the template strand with polarity ___(iii)___.

Select the correct option for (i), (ii) and (iii).
[0.7 mark]

• A.

  (i)	(ii)	(iii)
  $3^{\prime }\to 5^{\prime }$	$3^{\prime }\to 5^{\prime }$	$5^{\prime }\to 3^{\prime }$

• B.

  (i)	(ii)	(iii)
  $5^{\prime }\to 3^{\prime }$	$3^{\prime }\to 5^{\prime }$	$5^{\prime }\to 3^{\prime }$

• C.

  (i)	(ii)	(iii)
  $3^{\prime }\to 5^{\prime }$	$5^{\prime }\to 3^{\prime }$	$3^{\prime }\to 5^{\prime }$

• D.

  (i)	(ii)	(iii)
  $5^{\prime }\to 3^{\prime }$	$5^{\prime }\to 3^{\prime }$	$3^{\prime }\to 5^{\prime }$

Answer 1

The correct option is B

(i)	(ii)	(iii)
$5^{\prime }\to 3^{\prime }$	$3^{\prime }\to 5^{\prime }$	$5^{\prime }\to 3^{\prime }$

The DNA dependent DNA polymerases catalyse polymerization in $5^{\prime }\to 3^{\prime }$ direction. The replication is continuous on template strand with polarity $3^{\prime }\to 5^{\prime }$ . It is known as leading daughter strand. On the other template strand with polarity $5^{\prime }\to 3^{\prime }$, replication is discontinuous and this daughter strand is called lagging daughter strand.