Introduction to DNA structure

mRNA

Transcription

Introduction

The Central Dogma of Molecular Biology

Cell

Polypeptide(protein)

TranslationRibosome

Reverse tanscription DNA

DNA STRUCTUREchemical structure of the 4 nucleotides in DNA

DNA STRUCTURE hydrogen bonded nucleotides

on opposite helices

DNA helices are antiparallel

carbons on sugar define ends... 5' and 3'

pyrimidines bond with purines T A C G

DNA STRUCTURE bonding is specific: pyrimidines bond with purines implication: means for accurate replication

DNA STRUCTURE helical structure of DNA

major & minor groves

10Å radius & 20Å diameter

3.4Å between nucleotide base pairs

34Å / 360° turn

10 nucleotide base pairs / 360° turn

A TT AG CC

G

G C

TA

T

AG

C

C G

G C

T A

A T

Packaging DNA

Histone proteins

Histoneoctomer

B DNA Helix 2 nm

A TT AG CC

G

G C

TA

T

AG

C

C G

G C

T A

A T

Packaging DNA

Histone proteins

B DNA Helix

Histoneoctomer

2 nm

A TT AG CC

G

G C

TA

T

AG

C

C G

G C

T A

A T

Packaging DNA

Histone proteins

Histoneoctomer

Nucleosome

11 nm

B DNA Helix 2 nm

Packaging DNA

A TT AC G

C G

G C

T A

A T

Packaging DNA

A TT AC G

C G

G C

T A

A T

Packaging DNA

A TT AC G

C G

G C

T A

A T

Protein scaffold

11 nm“Beads on a string”

30 nm

Tight helical fiber

Looped Domains200 nm

Packaging DNA

G

C

A

T

Protein scaffold

Metaphase Chromosome

700 nm

11 nm

30 nm200 nm

2 nm

Looped Domains

Nucleosomes

B DNA Helix

Tight helical fiber

Replication

Chromosomes, Chromatids and Centromeres

Centromere

Chromosome arm

Chromosome arm

Identicalchromatid

Chromatid

Anaphase

A packaged chromosome

Two identical chromosomes

Chromosome Morphology

Chromosome arm

Chromosome arm

Centromere

Submetacentric Acrocentric TelocentricMetacentric

q arm

p armpetite

Chromosomes can be distinguished on the basis of size and the relative location of centromeres.

Human karyotype (of a man with a normal 46,XY constitution)