DNA Organization 6.5

Chromosome Structure the human genome consists of 23 pairs of chromosomes 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?

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

Chromosome Structure solenoid = a group of 6 nucleosomes coiled into chromatin fibres chromatin fibres fold into final chromatin structure through supercoiling.

Chromosome Structure See animation:

Prokaryotic DNA primary DNA is single circular chromosome supercoiling also in prokaryotes plasmids are other circular pieces of DNA that can be exchanged through conjugation

DNA Replication & Aging 6.6

Telomeres

non-coding, repetitive sequences at the ends of chromosomes protect chromosomes from degradation, fusing to other chromosomes, assist in DNA repair

Telomere Shortening during replication, the 5’ primer on each strand is removed but not replaced with DNA telomeres shorten after each replication after many replications, telomeres will eventually disappear, allowing coding DNA to be damaged

Cell Senescence period in a cell’s lifespan when it loses the ability to divide & grow Hayflick limit = total number of times a normal cell can divide (about 50 in humans)

Dolly the Sheep

Telomerase enzyme that adds more DNA to shortening telomeres produced in germ line cells, stem cells, certain white blood cells cancer cells produce large quantity of telomerase

Anti-Aging

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