Eukaryotic Chromosome Organization

Chromosome Organization• if all of the DNA was stretched out, it would measure

1.8 metres in length

• How does it fit into a typical human cell nucleus, 10 micrometres in diameter?

• there is a hierarchical organization

• DNA is coiled around a group of 8 stabilizing proteins called histones, forming nucleosomes

Chromosome OrganizationSee animation: http://www.biostudio.com/c_

%20education%20mac.htm

Histones

Linkers

Nucleosome(8 histones)

Solenoid(6 nucleosomes)

Supercoil

Prokaryotic DNA

Prokaryotic DNA

• primary DNA is single circular chromosome

• supercoiling happens in prokaryotes

• plasmids are other circular pieces of DNA contained in prokaryotes

• plasmids can be exchanged through conjugation

Telomeres

Telomeres• telomeres are non-coding, repetitive

sequences at the ends of chromosomes

Telomeres

Telomeres

Telomeres

• during replication, the last 5’ end primer on the lagging strand is removed but not replaced with DNA

• This shortens the telomeres on each subsequent replication cycle

» http://www.youtube.com/watch?v=8_bNfQd7Smc

QuickTime™ and a decompressor

are needed to see this picture.

Telomeres• after many replications, telomeres will eventually

disappear, allowing coding DNA to be damaged• cell senescence- deteriorated functioning with

age as chromosomes shorten• Hayflick limit = total number of times a normal

cell can divide (about 50 in humans)

Dolly the Sheep

Anti-Aging

Dani Walker “Stop Aging Now TS-X Telomere Supplement”

20

Homework

1. Read 6.5 for review.

2. Read 6.6 & answer:

a. What is the DNA sequence found in telomeres?

b. What is telomerase? What is its function? Where is it found?

c. What is the role of telomeres in aging?

d. What is the role of telomeres in cancer?

e. Complete the tables provided.