Taylor conducted the experiments to prove semi-conservative mode of chromosome replication on

(1) Vinca rosea

(2) Vicia faba

(3) Drosophila melanogaster

(4) E. coli

Semi-conservative replication of DNA was first demonstrated in

(1) Drosophila melanogaster

(2) Escherichia coli

(3) Streptococcus pneumoniae

(4) Salmonella typhimurium

Semi-conservative nature of the replication of eukaryotic chromosome was experimentally demonstrated by

(1)Chains

(2)Meselson and Stahl

(3)Hebert Taylor

(4)Hershey and Chase

How many times can the nuclear DNA replicate during the life cycle of a cell?

(1)Only once

(2)Twice

(3)Many times

(4)Does not replicate at all

In DNA replication, the two strands of a daughter DNA molecules are derived as follows

(1) one strand from parent DNA and the other freshly synthesized

(2) both strands from parent DNA

(3) both strands synthesized as templates on parent strands

(4) both strands synthesized on RNA templates of parent strands

DNA replication in most organisms is

(1)conservative and continuous

(2)semi-conservative but discontinuous

(3)semi-conservative and semi-discontinuous

(4)semi-conservative but continuous

In eukaryotes, the replication of DNA takes place

(1) at S-phase of the cell cycle

(2)before G2 and after G1phase of the cell cycle

(3) at M phase

(4)Both a and b

If an E.coli with heavy DNA allow to grow for 80 minutes in a culture medium of 14 NH 4

Cl, then what would be the proportion of heavy,light and hybrid densities DNA molecule

respectively?

1. 1/16 : 1/16 : 14/16

2. 0/16 : 14/16 : 2/16

3. 1/16 : 14/16 : 1/16

4. 1/8 : 2/8 : 6/8

Isotopes used in proving semiconservative replication of DNA were:

(1) ¹⁴N ¹⁴C            

(2) ¹⁴N ¹⁵N            

(3) ¹⁴N ³¹P             

(4) ¹⁴C ³¹P

Escherichia coli cells were grown for many generations in ¹⁵NH₄Cl as sole nitrogen source. Subsequently, these cells were grown exactly for four generations in medium containing ¹⁴NH₄Cl. The DNA from these cells were isolated and separated. If ¹⁵N/¹⁵N represents the two strands of DNA where both strands have heavy nitrogen; ¹⁵N/¹⁴N as intermediate DNA; and ¹⁴N/¹⁴N as DNA containing light nitrogen, the ratios for heavy: intermediate: light DNA, respectively would be:

(1) 1 : 0 : 7         

(2) 1 : 1 : 6         

(3) 0 : 1 : 7          

(4) 0 : 8 : 0