DNA replication animation- http://www.johnkyrk.com/index.html Fig 7.16

Fig 7.22

Sometimes errors are made.

Error Luckily, errors can be repaired. As they occur by DNA polymerase

How does E. coli know which strand is new?

Errors are made during DNA replication 3,000,000,000 (3 billion) base pairs/human cell with 1 error/1 billion base pairs not repaired = (average) ~6 errors each time DNA is replicated

Not all errors get repaired. These are mutations.

Telomeres are non-gene DNA at the ends of DNA strands.

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication.

The problem of replicating ends Fig 7.25

Telomere lengthening by telomerase Fig 7.26

Elongation of complementary telomere strand Fig 7.26

The telomere forms a protective cap on the end of the DNA with several cap proteins Fig 7.27

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication, and also by DNA damage.

Telomeres are non-gene DNA at the ends of DNA strands. Short telomeres will cause cells to stop replicating or cell death. The critical size is unknown.

Human Life Cycle high levels of telomerase very little telomerase

Why not produce telomerase all of the time? high levels of telomerase very little telomerase

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication, and by DNA damage. Short telomeres will cause cell senescence or cell death. Telomere size is a measure of mutations.

for W 11/7: Do telomere dynamics link lifestyle and lifespan? Pat Monaghan and Mark F. Haussmann TRENDS in Ecology and Evolution Vol 21 pg 47