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Day 9 September 21 Chapter 5
I will ask several clicker questions at
the beginningGET READY PLEASE!
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A chicken dinosaur? Scientists
discover what the bird might
have look liked in prehistoric
times
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Continuity and varietyLectures by Mark Manteuffel, St. Louis Community College; Clicker Questions by Kristen Curran, University of Wisconsin-Whitewater
Chapter 6: Chromosomes and Cell Division
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Bladder Cancer cells
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6.1 Immortal cells can spell
trouble: cell division insickness and health.
Once you are fully grown, do you have just one set of cells
that live as long as you do?
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Telomeres
The telomere is like aprotective cap at theend of the DNA.
Every time a cell
divides, the telomeregets a bit shorter.
(Like a cars odometer)
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At birth, the
telomeres inmost human cells
are long enough
to support about
50 cell divisions
Is there a Fountain of Youth?
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Cancer
These are cells
that rebuild
theirtelomeres
after each cell
division,
restoring theprotective cap,
never stop
dividing
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Cancer cells are thosewhich have forgotten
how to die.Harold Pinter
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6.2 Some chromosomes are
circular, others are linear.
prokaryote eukaryote
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6.3 Prokaryotes divideby binary fission.
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6.4 A time for everything: the cell cycle.
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6.5 Cell division is preceded by
replication.Persistence and propagation
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Replication
The process of DNA duplication
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Complementarity
the characteristic that in the double-stranded DNA molecule the base on onestrand always has the same pairing-
partner (called the complementarybase) on the other strand
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Complementarity
Every A (adenine) pairs with T(thymine) and vice-versa.
Every G (guanine) pairs with C(cytosine) and vice-versa.
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Mistakes sometimes occur
when DNA duplicates itself?
Why might that be a goodthing?
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Mutation
A variety of errors can occur duringreplication.
Several DNA repair processes occur afterreplication.
If an error remains, however, thesequences in a replicated DNA molecule(including the genes) can be differentfrom those in the parent molecule.
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6.6 Most cells are not immortal:mitosis generates replacements.
What isdust?
Why is it yourfault?
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Mitosis has just one purpose:
To enable cells to generate new,genetically identical cells.
There are two different reasons for thisneed:
1. Growth2. Replacement
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Mitosis
The number of (somatic) cells that mustbe replaced by mitosis every day is huge.
The rate at which mitosis occurs variesdramatically.
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6.7 Overview
Mitosis leads to duplicate cells.
Parent cells daughter cells
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Preparation forMitosis: The
ChromosomesReplicate
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Animal chromosomes are linear.
So why do they look like the letter
X in pictures?
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Sister Chromatids
A chromosome and its identical replicatedcopy, joined at the centromere.
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Tumor Growth
unregulatedcell division
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Cancer cells haveseveral features
that distinguishthem from normalcells, including
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Benign and Malignant Tumors
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Why is the treatment for cancer oftenconsidered as bad as the disease?
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6.10 Sexualreproduction
requires specialcells made bymeiosis.
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Meiosis
gametes
diploid
haploid
maintains a stable genome size in aspecies
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Meiosis achieves
more than just areduction in theamount of
genetic materialin gametes.
You have twocopies of everygene!
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Meiosis has two important features:
1. It reduces the amount of geneticmaterial in gametes.
2. It produces gametes that all differ fromeach other with respect to thecombinations of alleles they carry.
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6.11 Sperm and egg are producedby meiosis: the details, step-by-step.
Mitosis occurs almosteverywhere in an animals body.
Meiosis only occurs in one place.Where?