“bitter enders”. june pais & mark hens janet braam elizabeth eich marvin o’neal maurice...
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“Bitter Enders”
June Pais & Mark Hens
Janet BraamElizabeth EichMarvin O’Neal
Maurice KernanDavid CapretteCheryl BaileyT. Jack Morris
June Pais & Mark Hens
June Pais & Mark Hens
Janet BraamElizabeth EichMarvin O’Neal
Maurice KernanDavid CapretteCheryl BaileyT. Jack Morris
fluorescent probe for TTAGGG
GOAL: Understanding chromosome end replication
Target: Cell biology course for sophomoresPrereq: 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 DNA new DNA RNA primer
5’
3’
Review from a previous lectureThink/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 strandB. Bottom strandC. Both strandsD. Neither strandE. Not enough info
template DNA new DNA RNA 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 strandB. Bottom strandC. Both strandsD. Neither strandE. Not enough info
template DNA new DNA RNA primer
5’3’
5’
3’
5’3’
5’3’
Replicating chromosome ends
template DNA new DNA RNA 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
reneuvehttp://www.curebum.com/reneuve-telomerase-enzyme/
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)