Genomes and Genetic Architecture

Life on Earth

Operons are a prokaryotic variant of gene organization

Lower (yeast) and more advanced (anything but the damned yeast) eukaryotes

typical genome structures:

Gene size and mRNA size

Taxa Average exon number Average gene length (kb)

Average mRNA length (kb)

Hemophilus influenzae (prokaryote)single celled prokaryotic microorganism

1 1.0 1.0

Methanoccoccus jannachii (prokaryote)single celled prokaryotic microorganism

1 1.0 1.0

S. Cervisiae (Fungi, eukaryote)single celled eukaryotic microorganism

1 1.6 1.6

Filamentous Fungi (eukaryote)multicellular eukaryotic microorganism

3 1.5 1.5

C. Elegans (nematode, eukaryote)multicellular eukaryote

4 4.0 3.0

D. melanogaster (fruit fly, eukaryote)multicellular eukaryote

4 11.3 2.7

Chicken (eukaryote)multicellular eukaryote

9 13.9 2.4

mammalsmulticellular eukaryote

7 16.6 2.2

Gene Topography

Bacterium

Saccharomyces

Drosophila

Homo sapiens

Intergenic region exon intron

geneIntergenic region

Numbers of Exons per Gene

Histone genes - tandem repeats

Chromosome Duplication and Disjunction

Mouse Simple Sequence Centromere DNA Probes Autoradiographed

Dispersed Reptitive DNA

• VNTRVariable number tandem repeatsminisatellite DNADNA fingerprints

• Dinucleotide repeats

microsatellite DNA

VNTR

Retroelements

use reverse transcription

RNA to DNA

Retro Elements

• Transposons and Retrotransposons

– LINES - Long interspersed elements (1-5 kb, 20,00-40,000 copies per genome in humans)

• Alu (sequence similar to 7SL RNA, involved in transport through ER)

– SINES - Short interspersed elements

Repetitive Elements - HGO gene (alkaptonuria)

Spacer DNA

function unknown

may have functions …may reflect our ignorance

DNA Packaging

Chromosome Structure

A eukaryotic chromosomal landscape

Chromosomes

Nucleolus and rRNA genes

HumanKaryotype