Organization of DNA

the complete genetic makeup of an organism, its total DNA sequence

Genome*

Genes*units of heredity that are passed on from

parent to offspringdetermine, in whole or in part, a genetic

traitsegments of DNA responsible for the

production of a functional proteinevery person has two copies of each

gene, one inherited from each parent

Complexity and GenomeNo correlation between complexity of organism and …

• # of protein-coding genes (rice)• genome size (example lungfish)• # of protein-coding genes and genome size

• genes are not evenly spread along chromatin or chromosomes

Organization of genetic information*

• Viral• RNA or DNA, ss or ds, linear or circular

• Bacterial• DNA, ds, usually circular• found in one area = nucleoid• often have Plasmids (small extra-chromosomal DNA)

• Eukaryotic• DNA, ds, linear ds =double-stranded, ss=single-stranded

Eukaryotic chromosomes

Because we have A LOT of DNA in each cell it needs to be packaged in a specific way

Packing of DNA into chromosomes (1)*

Level 1Winding of DNA around histones to

create a nucleosome structure.

Level 2Nucleosomes connected by strands

of linker DNA like beads on a string.

Packing of DNA into chromosomes (2)*

Level 3Packaging of nucleosomes into 30-

nm chromatin fiber.

Level 4Formation of looped domains.

Packing of DNA into Chromosomes(big picture)

Packing of DNA into Chromosomes(big picture)

Isn’t that a lot of proteins ?*

Chromatin:- about twice as much protein as DNA

Two major types of proteins:1. Histones2. Non-histones

Isn’t that a lot of proteins ?

Two major types of proteins:1. Histones- abundant, basic proteins with a positive

charge that bind to DNA- evolutionarily conserved

2. Non-histones- all the other proteins associated with DNA- differ markedly in type and structure

Your ChromosomesChromosomes are compact molecules of DNAA human set of chromosomes contains 23 pairs23rd pair are your

sex chromosomesKaryotype

http://www.youtube.com/watch?v=ubq4eu_TDFc&list=PLF9969C74FAAD2BF9&index=1