Chapter 11

the complex of DNA and protein

regulatory (transcription), replicative, and histones

It shows the importance of the histones and the importance of their function. They are made of mostly basic amino acids.

• includes histone H1
• complex of proteins

Beads on a string allow the 6x compaction

30-nm fiber allow the 7x compaction

Packages the nucleosomes together. 

It is the common structure in euchromatin, an actively transcribed region

Loops of DNA organized in th 30-nm fiber are looped and anchored to the nuclear matrix. 

Nuclear matrix may be analogous to the cell cytoskeleton

Attachment of DNA via AT-rich segments: MARS and SARS

Possible function for junk DNA

heterochromatin: trnscriptional inactive regions

• metacentric: in the center
• submetacentric: a little off center
• acrocentric: more towards the end
• telocentric: at the end

repetitive DNA--> alphoid DNA (171 bp repeat)

CENP-A instead of H3, allowing more rigidity, which is thought to be positioned on the outside of the centromere and serves as a platform for kinetochore assembly

construction of chromosome specific fluorescently labeled dyes

hybridization to metaphase spread

individual metaphase are specifically "painted" a different fluorescent color

5'-TTAGGG-3'

5'-CCCTAA-3'

• TRF1 (regulates length) 
• TRF2 (protects overhang)

3'

a DNA structure where the two strands of a double-stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA

replicative sensence

cells no longer divide

it is the start checkpoint. Is the environment favorable?

ex: Wnt present; cell commits to replicating DNA and going all the way through the cycle; autopilot

Also, is DNA damaged

internal:

• - has DNA been replicated correctly (inhibits S-phase transition)
• - are they lined up
• - are there broken or mismatch chromosomes

internal checkpoint: is all DNA replicated

Is environment favorable

metaphase-to-anaphase transition

trigger anaphase and proceed to cytokinesis

are all chromosomes attached to the spindle?

cyclins and Cdks

cyclins bind to Cdk

Telomerase expression is shut down in somatic cells. If you had a cell that is lost, for example, APC, it will proliferate more, creating a selective evolutionary pressure to express telomerase. It will have increased fitness compared to cells in the neighborhood

a set of criteria that need to be satisfied in order for cell transition to the next phase of the cell cycle

• cyclins
• corresponding CDKs

transitions

CDKs and cyclins

Cdk complex

G1/ S- Cdk--> allows movement into S phase and production of S-cyclin

S-Cdk--> allows DNA replication

M-Cdk-- allows movement into the M phase

APC/C: anaphase - promoting complex that allows anaphase to proceed

accumulation allows them to allow the transition tooccur

activation via phosphorylation by Cdk-activating kinase (CAK). The T-loop is phosphorylated

inactivation by phosphorylation. There is another phosphate added that is an inhibitory phosphate. p27 attaches to form the p27-cyclin-Cdk complex

A t-loop is formed when the single-stranded 3' strand is looped back and anneals to the double-stranded hexamer repeats; as the G- rich strand displaces one strand a D, or displacement loop, is created

• tyrosine kinase receptors
• G protein coupled receptors
• integrins
• etc.

regions of active gene expression are transcribed first

cyclin activates it, which activates MCM helicase, which unwinds the helix at the origin of replication.

opening up the DNA, which occurs at origins of replication. They exist, but are quiet until the G1/S phase transition, where they will fire.

Cdc6P accumulates and binds to the origin of replication, calling MCM helicase.

shogoshin