Download Mitosis and Cell Division

http://kmarsh2.umwblogs.org/2008/10/24/cartoon-mitosis/
Nice animation, includes
recombination
http://www.johnkyrk.com/meiosis.html
Mitosis and Cell Division
Mitosis and Cell Division
Goals:
• Scaling: Nucleotide, Gene,
Chromosome--and how many of each
• Differences between mitosis and
meiosis
• Predict and describe meiotic results
• Master concepts referred to by: allele,
dominant, recessive, linkage
Mitosis and Cell Division
• You run a cake-making company
• Order comes in for a cake
• What information do you need?
– It’s ‘old-fashioned’- no photos
Scaling
•
A gene is ~1,000-100,000
basepairs*
•
A chromosome is tens or
hundreds of thousands of
genes
•
A genome is 1-100s of
chromosomes
•
A genotype refers to the
alleles present in a given
genome
•
Human genome is
~3,000,000,000 basepairs
•
Human genome is (currently
guesstimated at) ~20-30,000
genes**
•
Human genome is ~1 meter of
DNA
Mitosis and Cell Division
Mitosis and Cell Division
• Gene: Segment of DNA that represents all information for a
product as well as when and where to make the product
• Allele: A version (or flavor) of a gene; two alleles of the same
gene my differ by a nucleotide or dozens of them--generally a
small number
• Dominant/recessive: Two alleles enter; one allele leaves
(which version manifests in the organism) NOT which version
is more common!
• Mitosis vs Cell Division
• More in the lab manual & Vocab exercises!
Windows on the gene: eyes
• Find a brown- and a blue-eyed person.
Look deep into their eyes & try to figure out
the difference
• What does it mean genetically when we say
‘brown eyes are dominant’?
– One gene, two alleles
• Why should that be so? What do brown
alleles got that blue do not?
‘Ripped’ from Headlines
• Blue eyes arise from a DNA change that prevents
creation of melanin in the eye specifically
• Mutation appears identical in all blue-eyed folks
Meaning?
• Headline: Blue eyes result of ancient genetic
‘mutation’
– It’s not a ‘mutation’; it’s a mutation
A Couple Things to Think
About…
Mitosis and Cell Division
• How many cells
– When you were “0”?
– Now?
• What do cells DO?
https://eapbiofield.wikispaces.com/file/view/12_05CellCycle-L.jpg
What happens in each “Stage?”
What if a cell isn’t “listening”?
• Malignant Tumor – grows
aggressively, invades surrounding
tissue, metastasizes
• Benign Tumor – lacks malignant
tumor’s properties
• Benign tumors CAN cause “mass
effects”
What if a cell isn’t “listening”?
• Carcinoma - external/ internal
coverings of body
• Sarcoma - support tissues (bone,
muscle)
• Leukemia, lymphoma - bloodforming tissue cancers
And now, back to our program
It’s all in a name
•
•
•
•
•
•
•
•
•
Chromosome
Gene
Chromatid
Allele
Homologous
Dominant
Recessive
Spindle Fiber
Centromere
1 “Chromatid” can also be a chromosome;
it has all the genes on it.
1 “Chromatid” can also be a chromosome;
it has all the genes on it.
1 “Chromatid” can also be a chromosome;
it has all the genes on it.
This
1 “Chromatid” can also be a chromosome;
it has all the genes on it.
This
Is just a copy
of this
So, in this scenario…
From Mother
Chromosome 1
Chrm 2
From Mother
Chromosome 1
Chrm 2
From Father
Chromosome 1
Chrm 2
This is a DIPLOID
Nucleus/Cell
Chromosome 1
(from mother)
Chromosome 1
(from father)
Chromosome 1
(from mother)
Chromosome 1
(from father)
Copied during
Interphase
Copied during
Interphase
Chromosome 1
(from mother)
Copied during
Interphase
Chromosome 1
(from father)
Copied during
Interphase
So after replication…
So after replication…
Chromosome 1
(from mother)
Chromosome 1
(from father)
Chrm 2
Chrm 2
Condensed versions during mitosis/meiosis
This is ALSO a diploid
nucleus/cell
This is a DIPLOID
Nucleus/Cell
Mitosis and Cell Division
Why are
chromosomes
usually shown
like this?
Back to program
Pay attention to
the ‘nubbins’
Mitosis and Cell Division
• What do our bead
models represent?
Mitosis and Cell Division
• SHOW ME
• You can do a lot of fuzzy math (and fuzzy
biology and fuzzy chemistry and fuzzy...)
up there
• Drawing/speaking/writing forces precision;
reveals missing links
Mitosis and Cell Division
• Pick two traits
• Pick a dominant & recessive outcome
arising from different alleles
• You all start off heterozygous
Mitosis and Cell Division
• Point at some of your cells that ‘do’
mitosis?
• What’s the goal/purpose of this thing
called ‘mitosis’?
• So what must the first step be? Do it.
Mitosis and Cell Division
• Let’s do it
• What are ‘homologous’
chromosomes?
• How does ‘cell’ know they
go together?
Mitosis and Cell Division
• Point at some of your cells that ‘do’
mitosis?
• What’s the goal/purpose of this thing
called ‘mitosis’?
• So what must the first step be? Do it.
• Now what must be achieved?
– Any half? If not, how pick the appropriate
half?
• How do your final results compare with
starting?
Mitosis and Cell Division
• What comes after MITOSIS?
Meiosis
• Why have sex?
• What do you want the cells to
look like at the end of meiosis?
• How much are you ‘like’ your
mom and dad?
• Do ‘mother’ chromosomes
have to stay together?
Meiosis
• Let’s do it
• How diverse are your
‘gametes’?
• Is that enough?
Meiosis
• Recombination
• ‘Homologous’ chromosomes
can exchange genes
Meiosis
Where should the circled site on
Chromo1 recombine with Chromo2?
1
2
3
Meiosis
• Pick two ‘traits’
• What is dominant/recessive?
Meiosis
• First, make a copy--b/c that’s the way it
happens
• Pair the pairs: duplicated mom’s &
dad’s contributions pair
• Recombine (randomly)
Meiosis
• Now we’ve recombined; how to
separate?
• When is a cell haploid?
• Select a gamete, go fuse with a
classmate
• Stop by and show me the genotype
Meiosis
• Diversity?
• Two chromosomes with
recombination
• How many possibilities?
Meiosis
• Crossing Over is GREAT for
genetic diversity!!!
• What are the ‘costs’?
Things go wrong during Meiosis
•
•
•
•
Non-disjunction
Insertion
Deletion
Inversion
Meiosis
Clean Up
No, we’re NOT done
More Vocab…
• We’ve talked about chromosomes,
mitosis, and meiosis…
• Recombining genes via Crossing
Over
• How likely do you suppose it is
that genes are inherited together?
More Vocab…
• Linkage’ - referring to whether
genes are inherited together
because they are ‘close’ on a
chromosome
• ‘Linked’ - referring to the resulting
behavior of traits encoded by such
genes
Gameter
• Open Gameter
• Move things around, work with the
buttons
• Notice A and a go together
• End up with: ‘A’ and ‘B’ on Chrm
II, with A farther right than B
• Ab and AB
Gameter
• Explore
– One meiosis
– 200 meioses
– Move ‘em around and try again
•
•
•
•
Observe
Hypothesize
Test
Evaluate
Disease Presentation
Research Project
Where we’re headed
• Your proposal is an answerable,
interesting question
• It will reflect causation
• Follow rubric – choose a proposal
Take a look
• Onion root tip – make it a squash
• Grasshoppers testes
Mitosis (with just ONE set of
chromosomes) looks like this…
Two IDENTICAL
DIPLOID cells
+
Both cells are still DIPLOID because
they have TWO chromosome #1s
+
When they replicate their DNA, each
will look just like the parent cell
Show Me
MEIOSIS (with TWO sets) looks
like this…
Meiosis 1
+
Each of these cells
is HAPLOID as it only has
ONE set of chromosomes
(1 of each; chrm 1 and chrm 2)
Meiosis 2
Four DIFFERENT
HAPLOID cells
Back to the Cell Cycle
Cells spend most of their
“lives” like this
They only look like this after
they replicate their DNA in
order to divide (mitosis)
• HOMEWORK
• Proposal!!!!!!!