How do cells make a copy of their DNA?
Conservation of the genetic code
When cells make copies of their DNA, the copying is almost exact.
However, a small number of mistakes may occur. We call this a mutation.
Why is DNA double-stranded?
Isn’t that a waste to have a gene written twice?
It It Would Would Like Like Be Be Writing Writing Each Each Word Word Twice Twice
Cells do this because it allows copies to be made exactly & quickly.
Basic idea
Step-by-step details
Looking at the base pairing, up close
Hands-on lab with M&Ms
We can use M&Ms or other colored candies to stand in for DNA nucleotides.
Start by color coding them. In this class we chose
Yellow M&M = G Green M&M = C
Blue M&M = A Orange M&M = T
Then lay out the structure.
We next add a bunch of extra M&Ms, representing DNA nucleotides synthesized by the cell.
They are single, not connected to anything, just floating nearby (here, at the bottom.)
Then, one M&M at a time, we should how they connect to the open parts of the gene:
Videos
This process is mind-bogglingly fast. This video shows the amazing speed at which this takes place:
KaiserScience 