Natalia Sivackova

Introducing DNA

SubunitsMade of simple subunits called nucleotidesConsists of 3 parts:1.Sugar (deoxyribose)2.Phosphate group3.Base

phosphate

sugar base

NucleotidesNucleotides do not all have same baseFour different bases:1.Adenine (A)2.Cytosine (C)3.Guanine (G)4.Thymine (T)

Building DNA MoleculesTwo nucleotides link

together by a covalent bond

DNA = two strands of nucleotides wound together

Complementary base pairing: A – T and C – G

DNA ReplicationCopying DNA to produce new molecules

with same base sequenceSemi-conservative: one new strand and

one old conserved from parent DNA3 Stages:

Stage 1Double helix is unwound Breaking the hydrogen bondsEnzyme involved: Helicase

Stage 2Single strands act as templatesFree nucleotides attach (form hydrogen

bonds)Main enzyme involved: DNA Polymerase

Stage 3• Rewind into double helix

VocabularyNucleotidesAdenineCytosineGuanineThymineCovalent bondComplementary base pairingSemi-conservative

Bibliographyhttp://www.biology-online.org/1/5_DNA.htmhttp://www.scq.ubc.ca/a-monks-flourishing-

garden-the-basics-of-molecular-biology-explained/

http://qwickstep.com/search/hydrogen-bonds-dna.html

http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect02.htm

References:Study GuidePg. 16Course CompanionPg. 54-58Pearson HLPg. 55-60