Nucleotides, Nucleic Acids, Cell Division, Cell Diversity and Cellular Organisation Key Terms and Definitions

Question 1

Describe DNA replication

Answer 1

• DNA is unwound from histone proteins, double helix is unzipped by DNA Helicase (breaks 2 H bonds between A and T, and 3 H bonds between C and G)
• when strands separate a replication fork is formed
• DNA polymerase binds to the 3’ and of the leading strand and moves down and pairs new complimentary nitrogenous bases together; adenine to thymine, cytosine to guanine (built up in the 5’ to 3’ end)
• the same will happen to the other side but in the other direction, once the whole of the DNA has been replicated =, DNA ligase seals up the sequence of DNA into continuous double strands
• this method of DNA replication is known as semi conservative, as one strand of the replicated DNA is old, and O=one is newly synthesised