Structure of DNA

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HomeworkDefine (Page 362-365)

RNA

Messenger RNA

Ribosomal RNA

Transfer RNA

Transcription

RNA polymerase

Promoter

Intron

Exon

Review Homework

List the conclusions that Griffith and Avery drew from their experiments?

Griffith concluded that heritable substance transforms harmless bacteria into harmful bacteria. Avery found this is DNA

Review Homework

What was the experimental variable that Avery used when he repeated Griffith’s work?

Molecule-destroying enzyme he used

Review Homework

What conclusions did Hershey and Chase draw from their experiments?

DNA is the genetic material found in genes

Components of DNA

What does DNA stand for?Deoxyribonucleic acid

Made up of nucleotides joined into long strands and chains

Made up of 5 carbon sugar called deoxyribose and phosphate

Has 4 nitrogen bases: adenine, guanine, cytosine and thymine

Commonly referred to as A, G, C, T

Components of DNA

Nitrogen bases are bases that contain nitrogen

These bases stick out sideways from each other

Can be joined in any order

Structure of DNAErwin Chargaff

Showed percentages of adenine and thymine are almost always identical in DNA

Percentages of Guanine and Cytosine are also almost identical

What conclusion would you draw from this?

A=T

G=C

Structure of DNARosalind Franklin

Took x-ray diffraction pictures that revealed the double-helix structure of DNA

Only showed a 2-D model of DNA, but presents in X-shape

James Watson and Francis CrickBuilt a model of the DNA molecule that explained both structures and properties of DNA

Used Franklin’s x-shape to discover Double-Helix

The Double HelixThe double helix explains Chargaff’s rule of base pairing

Model shows:2 strands in double helix run in opposite directions with bases in the center

Each strand carries a sequence of nucleotides, arranged like letters of alphabet for recording genetic info

Hydrogen holds strands togetherChemically speaking, H bonds strong or weak?

H bonds form only between pairs (AT – CG)Base Pairing

The Double HelixLike a twisted ladder or a spiral staircase

Each strand is “antiparallel”Antiparallel?

Run in opposite directions

Base PairingThe perfect fit of Adenine with Thymine

Guanine and Cytocine

Why are the weak Hydrogen bonds important?

Think of the functions of DNA

Final QuestionsWhy did scientists have to resort to methods other than a microscope?

Explain the idea of base pairing?

HomeworkDefine (Page 362-365)

RNA

Messenger RNA

Ribosomal RNA

Transfer RNA

Transcription

RNA polymerase

Promoter

Intron

Exon