Question

Genetics Questions

1) Draw the molecular structure of a di-nucleotide of two DNA molecules as it would exist in a cell. Label the 5' ends, the 3' ends, and the phoshodiester bonds. Draw the ring structures of the nucleobases and label them.

2) List and describe the key events of DNA replication in their relative order for E. coli.

Answer 1

2. Key events of DNA replication are as follows -

•Helicase enzyme load on at the origin of replication and helps in opening of the DNA at the replication fork( small opening of DNA helix).

•To prevent rewinding of the DNA strand single- stranded binding protein is applied over DNA.

•Primase synthesises RNA primers which is complimentary to the DNA strand.

•DNA polymerase lll is the DNA maker enzyme which extends the primer adding on to the 3' end to make the new DNA .

•RNA primer is removed from the DNA and replaced by DNA polymerase l.

•The gaps created between the DNA fregments are sealed by the enzyme DNA ligase.

•DNA polymerase plays an important role in addition of the building blocks to the primer.