Class Notes (808,754)
Canada (493,378)
Biology (6,677)
Biology 1001A (1,723)
Tom Haffie (1,166)
Lecture 7

Lecture 7.docx

3 Pages
Unlock Document

Western University
Biology 1001A
Tom Haffie

Biology 1001A [Type text] October 1, 2012 Lecture 7  DNA Replication: 1. A-T; G-C 2. Pairing is antiparallel 3. Extend 3’ end of properly paired base  DNA polymerase cannot initiate DNA synthesis, they can only elongate/continue something that’s already started  Chromatids are identical DNA molecules attached at their centromeres  List of mechanisms to ensure inheritance of “sameness” 1. Complementary base pairing during replication  The last bubble on the end of the chromosome is removed and is not replaced  Telomerase elongates it and brings its own template and adds onto the 3’ end and the entire unit slides down and adds more DNA several times which creates a region on the end of the chromosome called a telomere, which is just repetitive DNA. Since the strand has been elongated, it can be primed as usual, and the space that could not have otherwise been replaced is now filled in with polymerase. The primer is lost, as usual, so there is a single stranded end hanging off the end of the chromosome forever. It bends around to make a “cap/lid” at the 3’ end so that the end of the chromosome is protected.  The same problem happens on both ends of the chromosome, just on different strands 2. Cytoskeleton is involved in the partitioning of chromosomes  Involved in making sure the chromatids get into the daughter cells  Intermediate filaments maintain the cell shape 3. Checkpoints regulate progression through cell cycle  Cells will not proceed into anaphase until all chromosomes are attached to spindle (metaphase checkpoint)  G1 checkpoint: cells won’t replicate the DNA until it is fully repaired  End of G2: are we ready to condense DNA and proceed to mitosis?  When/where are cells actively cycling in a bird?  Gamete cells  Bone marrow  Repairing  In the epidermis -> any tissue that needs to be renewed  Skin, lining of your gut  When/where are actively cycling cells in a tree?  Root tips  Shoots  Trunk  Most cells in mature multi-cellular organisms are not cycling actively! Biology 1001A [Type text] October 1, 2012  When/where might cells be programmed to die (apoptosis)?  Surplus -> their job to die, don’t need it  Neurons that aren’t being used  Plants -> xylem pipes are cells that died  Have mutations or infected by virus -> good if it just died  It might be the normal thing for cells to die by apoptosis  Nothing can prevent
More Less

Related notes for Biology 1001A

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.