DNA Replication Practice

DNA replication is copying DNA as needed for mitosis.  In order to copy DNA, an enzyme Helicase, has to unzip the DNA by cutting the hydrogen bonds between bases.  Another enzyme, DNA Polymerase, will then attach to each DNA strand and start building the second side of the DNA called the complimentary strand. 

• DNA is labeled by a 5’ and 3’ end.  DNA polymerase will only work from a 5’ to 3’ direction. 
  • One strand is 5’ and DNA polymerase can just build a continuous strand.  This is called the leading strand. 
  • The other strand starts with a 3’ so DNA has to build the strand is fragments called Okazaki fragments.  This is the lagging strand. 
    • An enzyme then has to join these fragments together to make a complete DNA copy. 

Each finished DNA strand is then made up of one old half of DNA and one new half of DNA.

Remember:  A binds to T and C binds to G

On the following questions, write the complimentary strand for the DNA strand given.  

For example:

I give you the strand   

• AGTCCAGATATTCCGA

You respond withe the complimentary strand

• TCAGGTCTATAAGGCT  (A turns into a T, G turns into a C and visa versa)