DNADNA

•Deoxyribonucleic Acid

• D – Deoxyribo

• N – Nucleic

• A – Acid

All Images- Clip ArtAll Images- Clip Art

DNA StructureDNA Structure

• Nucleotide Nucleotide – The monomer of The monomer of

DNADNA– Basic unitBasic unit– Consists of 3 parts Consists of 3 parts

Nucleotide- Part 1 (p197)Nucleotide- Part 1 (p197)

• 5 carbon sugar5 carbon sugar– Deoxyribose Deoxyribose

Nucleotide- Part 2 (p197)Nucleotide- Part 2 (p197)

• Phosphate groupPhosphate group

Nucleotide- Part 3 (p197)Nucleotide- Part 3 (p197)

• Nitrogenous Nitrogenous bases- 4 different bases- 4 different (p 198)(p 198)– Purines Purines

• adenine (A) adenine (A)

• guanine (G)guanine (G)

Nucleotide- Part 3 (p197) Nucleotide- Part 3 (p197)

• Nitrogenous bases- Nitrogenous bases- 4 different (p 198)4 different (p 198)– PyrimidinesPyrimidines

• thymine (T)thymine (T)

• cytosine (C)cytosine (C)

NucleotideNucleotide

• ModelModel • Pentagon = sugarPentagon = sugar

• Circle = phosphate Circle = phosphate groupgroup

• Square = nitrogen Square = nitrogen basebase

Shape of DNA (p199)Shape of DNA (p199)

• Double helixDouble helix– 2 spirals wrapped 2 spirals wrapped

around each otheraround each other

Ladder Model of DNA (p199)Ladder Model of DNA (p199)

• ““Uprights”- Uprights”- – 5 carbon sugar & 5 carbon sugar &

phosphatephosphate• ““Rungs”- Rungs”-

– Nitrogenous base Nitrogenous base pairspairs

– Base pairs held Base pairs held together by together by hydrogen bondshydrogen bonds

– A with TA with T– C with GC with G

• PP• **

• D - C ~ G- DD - C ~ G- D• ** * *• PP P P• ** * *• D - T ~ A- DD - T ~ A- D• ** * *• PP P P• ** * *• D- T ~ A - DD- T ~ A - D• * ** *• P PP P• ** * *• D - A ~ T- DD - A ~ T- D• ** * *• P PP P• ** * *• D - C ~ G- DD - C ~ G- D• ** * *• P PP P• ** * *• D - G ~ C- DD - G ~ C- D• **• PP

DNA Replication (p 201)DNA Replication (p 201)

• Process in which Process in which DNA makes exact DNA makes exact copies of itself in copies of itself in the nucleus.the nucleus.

DNA Replication (p 201)DNA Replication (p 201)

• DNA molecule DNA molecule “unzips” where the “unzips” where the hydrogen bonds hydrogen bonds hold the base pairs hold the base pairs together in the together in the rungs of the ladder.rungs of the ladder.

• Helicases- enzymes Helicases- enzymes that break hydrogen that break hydrogen bondsbonds

DNA Replication (p 201)DNA Replication (p 201)

• New nucleotides New nucleotides attach, one by one, attach, one by one, to the appropriate to the appropriate exposed bases of exposed bases of the DNA strandsthe DNA strands

• DNA polymerases- DNA polymerases- enzymes that add enzymes that add the bases to the bases to original strandoriginal strand

• PP• **

• D - C ~ G- DD - C ~ G- D• ** * *• PP P P• ** * *• D - T ~ A- DD - T ~ A- D• ** * *• PP P P• ** • D - TD - T• * * • P P • ** • D - A D - A • **• P P • ** • D - C D - C • ** • P P • ** • D - G D - G • •

DNA Replication (p 201)DNA Replication (p 201)

• The result is 2 DNA molecules from 1 The result is 2 DNA molecules from 1

DNA Replication (p 201)DNA Replication (p 201)

• Each molecule is Each molecule is identical to each identical to each other and the other and the original.original.

DNA Replication (p 201)DNA Replication (p 201)

• Semi-conservative ReplicationSemi-conservative Replication– Each newly formed DNA molecule is Each newly formed DNA molecule is

made up of one strand from the made up of one strand from the original and one strand that is new.original and one strand that is new.