Our Guiding Question • WHAT DETERMINES THE ORDER OF AMINO ACIDS IN A PROTEIN???
Warm-up • Which parts of the nucleotides are connected to make one strand (half) of DNA? • Which parts of the nucleotides connect the two strands (halves) of DNA? • What type of bond connects the two strands together? • If a DNA molecule is 30%Adenine how much Cytosine is there?
What does DNA look like? • We can describe its molecular structure • We can say what DNA looks like after isolation.
DNA replication How is DNA made?
DNA Replication Whenever a cell divides into two new cells, it needs to make an exact copy of the DNA. What would happen if a cell divided without DNA making a copy of itself? The process of copying DNA is calledDNA replication.
Enzymes in DNA replication • Enzymes are proteins that act as machines in the cell to do work. • 2 enzymes do the work of DNA replication: • Helicase is responsible for separating the 2 strands of DNA • DNA Polymerase is responsible for adding on new Nucleotides. We will replicate (copy) our DNA molecule in class to produce 2 new identical DNA molecules
Helicase • Helicase unwinds and separates the 2 strands of DNA so that each strand may be copied. • Helicase breaks the hydrogen bonds between the bases of each strand. Hydrogen Bonds
DNA Polymerase • DNA Polymerase adds on the complimentary bases to the new strands of DNA • DNA Polymerase makes bonds between the phosphate and the deoxyribose sugar of the nucleotides. DNA Polymerase
Complementary base pairing • If one strand of DNA has the following sequence, CTAATGT GATTACA What is the base sequence (order of nucleotides) for the complimentary strand?
Replication in Action • Replication occurs simultaneously at multiple places along a DNA strand. • 1 chromosome is about 80 million base pairs long. • Replication is as fast as 50 base pairs a second! Flash Animation: http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf