DNA Structure and Replication

DNA Structure (reading handout)

·      DNA’s shape is known as a double helix (it looks like a twisted ladder)

·      DNA’s main building piece is a nucleotide

·      Each nucleotide is made of a deoxyribose (sugar), phosphate and a nitrogen base.

·      The nucleotides connect in two places:

o       Between the phosphate and the sugar

o       Between the nitrogen bases

·      The “uprights” or sides of the DNA ladder are made of deoxyribose and phosphate

·      The “rungs” of the DNA ladder are made of nitrogen bases

·      The four types of nitrogen bases are:

o       adenine

o       thymine

o       cytosine

o       guanine

DNA Replication (pages 78-79)

• DNA replication needs to happen so that each daughter cell has an exact copy of the genetic information 

The Structure of DNA (page 78)

• DNA is in the shape of a twisted ladder known as a double helix
• Nitrogen base pairs form the rungs of the ladder
• In the base pairs, adenine (A) matches with thymine (T) and guanine (G) matches with cytosine (C)

The Replication Process (page 79)

• To replicate, DNA pulls apart between the base pairs
• New bases in the nucleus match up in the same A-T and G-C pairs
• The order in the new DNA molecule should exactly match the order in the old DNA molecule