Eukaryotic Chromosome Organization

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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 Organization http://sciencenetlinks.com/interactives/

dna.swf

Histones

Linkers

Nucleosome(8 histones)

Solenoid(6 nucleosomes)

Supercoil

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Chromosome Organization

• Solenoid = a group of 6 nucleosomes coiled into chromatin fibres

• chromatin fibres fold into final chromatin structure through supercoiling.

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

13

Telomeres

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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

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”

Homework

1. Read 6.5 & 6.6 answer: a. What is the DNA sequence found in telomeres of

vertebrates? 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. Read the articles provided on Telomeres.

a. summarize the effect of stress and home life on telomere length in a t-chart

b. What hope is there for improving aging based on the research?