Place the following steps of DNA replication in right chronological order. 1. Pr
ID: 253459 • Letter: P
Question
Place the following steps of DNA replication in right chronological order.
1. Primase adds an ribonucleotide primer
2. Initiator proteins bind the origin of replication and helicase breaks hydrogen bonds between complementary bases of double stranded template DNA
3. DNA polymerase III extends by complementary base pairing deoxyribonucleotides to the template strands
4. Ligase phosphodiester bonds the nucleotides to connect okazaki fragments nad connect fragments at the origin and where the "crotches or forks" collide
5. DNA polymerase I removes RNA primer and replaces with Deoxyribonucleotides
Explanation / Answer
1. The first step should be “Initiator proteins bind the origin of replication and helicase breaks hydrogen bonds between complementary bases of double stranded template DNA.”
In this step, the initiator protein is the RNA polymerase. It binds to ‘Ori’; DnaB is the helicase which breaks the hydrogen bonds.
This step is commonly known as initiation.
2. The second step should be “Primase adds a ribonucleotide primer.”
3. The third step is “DNA polymerase III extends by complementary base pairing de-oxy-ribonucleotides to the template strands.”
This step is commonly known as elongation.
4. The 4th step is “DNA polymerase I removes RNA primer and replaces with De-oxy-ribonucleotides.”
5. The final step of this scheme should be “Ligase phosphodiester bonds the nucleotides to connect Okazaki fragments and connect fragments at the origin and where the "crotches or forks" collide.”
Ligase acts to fill up the gaps created by DNA polI.