Bitter Enders June Pais Mark Hens Janet Braam

“Bitter Enders”

June Pais & Mark Hens Janet Braam Elizabeth Eich Marvin O’Neal Maurice Kernan David Caprette Cheryl Bailey T. Jack Morris

GOAL: Understanding chromosome end replication Target: Cell biology course for sophomores Prereq: Intro biology fluorescent probe for TTAGGG

Learning Goal: Understanding chromosome end replication Learning Objectives: • Describe the problem caused by the requirement for primers in the replication of the lagging strand. • Predict the consequence to chromosome lengths after multiple rounds of cell division. • Explain how telomere repeats prevent loss of information. • Explain how the mechanism of chromosome end replication limits the number of possible cell divisions in most somatic cells. • Explain how the presence or absence of telomerase may affect the replicative life-span of cells.

Review from a previous lecture Think/Pair/Share: Describe DNA replication to your neighbor using this diagram and the terms below: 3’ 5’ 5’ 3’ Template DNA new DNA RNA primer

Chromosomal DNA replication RNA primer 3’ 5’ 5’ 3’ Template DNA new DNA *

Replicating chromosome ends 3’ 5’ At this end of the chromosome, which strand cannot be completely replicated? A. Top strand B. Bottom strand C. Both strands D. Neither strand E. Not enough info 3’ 5’ template DNA new DNA RNA primer

Replicating chromosome ends 3’ 5’ Template for lagging DNA strand Template for leading DNA strand The lagging strand cannot be completely replicated. template DNA new DNA RNA primer

Analogy: Class notes Copier This copier never copies the last page. How would you prevent information loss?

Information loss during replication Essential genes here Genes lost! - cells die!

Delaying information loss during replication “page” = Telomere repeat Essential genes here - cells die!

Solving the information loss problem Telomere repeat Essential genes here Telomerase!

The Nobel Prize in Physiology or Medicine 2009 Elizabeth H. Blackburn, Carol W. Greider, Jack W. Szostak Telomerase!

Homework: Will you? ” http: //www. curebum. com/reneuve-telomerase-enzyme/ reneuve

What is a bitter end? A. A cultural reference to an angry person. B. Biological reference to a zombie’s “rear end”. C. The inboard end of an anchor cable, which is fastened to the bitts at the ship’s bow. D. The part of the cucumber that no one eats. E. A famed Bleecker Street landmark pub.

Diversity • • Multimodal (activities) Women in science (Nobel Prize) Group assignments Rotating group roles (reporting out)