1. Lesson 3 Thursday, 11/14 AIM: What is a telomere?
How is DNA proofread?
DO NOW: List the enzymes used in DNA replication.
HW: Complete Ch. 13 MC
Study all notes
Read photosynthesis lab and do on line

2. RNA primase and RNA primer

3. A gap remains unfilled on the leading strand b/c DNA polymerase can add only to the 3’ end.

4. Aging and DNA Replication
no way to complete the 5’ ends of leading daughter DNA strand.
Repeated rounds of replication produce shorter and shorter DNA molecules.

5. Telomeres the ends of eukaryotic chromosomal DNA molecules
protect genes from being eroded through multiple rounds of DNA replication.
have special nucleotide sequences, typically TTAGGG, repeated between 100 and 1,000 times.
planned senescence

6. Telomerase
PRESENT IN:
NOT PRESENT IN:

7. Proofreading of DNA
Mistakes during base pairing occur at a rate of 1 error per 10,000 base pairs.
DNA polymerase proofreads, and the final error rate is only one per billion nucleotides.

8. Errors after initial proofreading:
Chemicals, radioactive emissions, X-rays, and UV light can change nucleotides (mutations)
Spontaneous chemical changes of bases under normal conditions
Some mismatches are missed by DNA polymerase

9. 2 types of DNA repair enzymes:
Mismatch repair:
Nucleotide excision repair:

10. Xeroderma pigmentosum
Autosomal recessive
Defect in nucleotide excision repair
formation of thymine dimers Leads to skin cancer