dna organization 6.5. chromosome structure the human genome consists of 23 pairs of chromosomes if...

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DNA Organization 6.5

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Page 1: 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

DNA Organization

6.5

Page 2: 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

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?

Page 3: 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

Hierarchical Organization

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

Page 4: 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

Chromosome Structure

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

• chromatin fibres fold into final chromatin structure through supercoiling.

Page 6: 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

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

Page 7: 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

DNA Replication & Aging

6.6

Page 8: 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

Telomeres

Page 9: 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

Telomeres

• non-coding, repetitive sequences at the ends of chromosomes

• protect chromosomes from degradation, fusing to other chromosomes, assist in DNA repair

Page 10: 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

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

Page 11: 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

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)

Page 12: 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

Dolly the Sheep

Page 13: 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

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

Page 14: 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

Anti-Aging

Page 15: 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

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