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 contained in prokaryotes plasmids can be exchanged through conjugation

Telomeres

telomeres are non-coding, repetitive sequences at the ends of chromosomes during replication, the 5’ primer on each strand is removed but not replaced with DNA telomeres shorten after each replication

Telomeres after many replications, telomeres will eventually disappear, allowing coding DNA to be damaged cell senescence 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”