DNA Chapter 12 Lecture One Deoxyribonucleic Acid Long

DNA Chapter 12 Lecture One

Deoxyribonucleic Acid • Long molecule • Made up of many connected nucleotides (the multi-part subunit of DNA) • 5 -C sugar, phosphate, nitrogenous base

Deoxyribonucleic Acid Backbone of DNA is made of 2 alternating parts • 5 -carbon sugar – deoxyribose • Phosphate group

DNA is a polymer of nucleotide monomers “backbone” of sugar and phosphate groups Phosphate 5 -C sugar Phosphate 5 -C sugar The 2 strands are zipped together by hydrogen bonds Phosphate 5 -C sugar Phosphate “rungs” of the ladder are nitrogenous bases

The DNA molecule is a double helix

Base-pairing Rules • Adenine (A) always pairs with Thymine (T) • A • • T or T • • A • Connected by 2 Hydrogen bonds • Cytosine (C) always pairs with Guanine (G) • C • • • G or G • • • Connected by 3 Hydrogen bonds

The base pairing rules are determined by the ability of some combinations of Nbases to form hydrogen bonds between them.

Deoxy ribose T C C T T Deoxy ribose P P G A These three molecules make up a nucleotide A

Phosphate group P A Nucleotide Covalent bonds C Deoxyribose Nitrogen containing base Sugar

Backbone of DNA molecule P Deoxy ribose P Bases – “rungs of the ladder” Deoxy ribose

Backbone of DNA molecule P Deoxy ribose C P G Deoxy ribose P Bases – “rungs of the ladder” Deoxy ribose T

Hydrogen bonds ■■■■ C G Deoxy ribose P P P G ■■■■ C Deoxy ribose P P Deoxy ribose ■■■■ A Deoxy ribose T P