“Bitter Enders”

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

June Pais & Mark Hens

Janet Braam Elizabeth Eich Marvin O’Neal Maurice Kernan David Caprette Cheryl Bailey T. Jack Morris

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

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. Learning Goal: Understanding chromosome end replication

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

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

Replicating chromosome ends 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 template DNAnew DNARNA primer 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’

Replicating chromosome ends 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 template DNAnew DNARNA primer 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’

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

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

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

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

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

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

reneuve Homework: Will you?”

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)