Transcript Part 4: EOC Review PowerPoint

Biology EOC Review
Biological Molecules and Membranes/Cell
Structure/Mitosis/Meiosis and Genetics
Part 4
If you recall…
 We’ve already discussed that all cells are alive
because they use their cellular structures to react to
their environment and they have found a means to
generate energy to live.
 So, why do they need all of these complex processes
to make energy?
 So they can reproduce.
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Making More
 So, let’s say that a plant cell is minding its business.
 Then, all of a sudden, it receives a chemical message on
its cell membrane that it needs to repair damage to the
tissue it’s living in.
 What does the cell do?
 Well, it’s got to make a copy of itself.
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Asexual = cloning
 This type of copying is asexual reproduction, which
happens whenever there is growth or damage to the
organism.
 Some people prefer to use the term cloning instead.
 Anyway, the cell has to get ready for this massive
use of energy, which is why asexual reproduction
does not happen instantly.
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The Cell Cycle
 The process that a cell has to go through to clone itself is
pretty time consuming and uses up a lot of energy.
 We call this process the Cell Cycle.
 Basically, the cell first gets ready by building up the
necessary parts it will need or the Interphase stage This
can be further broken up into the G1 or first growth, the
S or DNA synthesis , and the G2 or final growth.
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The Cell Cycle
 Once the cell is large enough, has the right amount
of extra cell parts, and has copied its DNA, it’s
ready to split in two.
 Splitting in two is called Mitosis.
 Mitosis is fast, requires no partner, guarantees that
100% of your genes get into the future generation,
but it does not allow for diversity.
 Bummer.
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The Cell Cycle/Mitosis a Review
 Animation: How the Cell Cycle Works
 MITOSIS - MADE SUPER EASY - ANIMATION
 Mitosis: The Amazing Cell Process that Uses
Division to Multiply!
 The Cell Cycle and Cancer
 Mitosis Rap: Mr. W's Cell Division Song
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Bring in the Clones
 Great, the damage is healed because we made more
of the same plant cell.
 Awesome.
 What would happen if all of a sudden the climate
changes?
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Bring in the Clones
 Now there is less of the correct wavelength of light
needed for our little plant cells to make energy.
 Now what?
 The plant cells really don’t have many options.
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Adapt, Move, or Die
 It’s not like they can change the climate back to
what it was like before.
 They really don’t want to die.
 They really can’t move to a better climate.
 They may want to adapt, but that takes time.
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Adapt, Move, or Die
 This is the problem with using asexual reproduction
as the only means to make new cells.
 If the climate changes, there is a disease, they get
eaten,… all of the cells and the organism they are
living in may not survive.
 So, there has got to be a better way.
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It’s all about sex
 The solution to the little plant cells’ problems is
sexual reproduction.
 That’s why S-E-X is such a big thing.
 It gives cells and organisms a chance to survive in a
climate that is changing.
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It’s all about sex
 Not surprisingly, it takes a LOT MORE energy for
an organism to reproduce sexually than it does to
reproduce asexually.
 For this reason, not every cell has the ability to
reproduce sexually.
 Sexual reproduction only occurs in certain parts of
an organism.
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It’s all about sex
 Prokaryotic Bacteria use this technique to reproduce
sexually, only when they think it is advantageous to
do so, i.e. when the environment is just right.
 Eukaryotic Plant Cells use flowers and other sexual
reproduction organs.
 Eukaryotic Animal Cells use a reproductive system.
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Meiosis
 Remember the Cell Cycle and Mitosis in the asexual
reproduction section?
 Cells that reproduce sexually also go through a Cell
Cycle and a process called Meiosis, which has more
than twice the number of steps than Mitosis.
 So, in Meiosis, we wind up with four new cells.
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Meiosis
 Meiosis takes longer than mitosis and it takes more
energy than mitosis.
 You need a partner for meiosis. You don’t need one
for mitosis.
 Meiosis gives you diversity. Mitosis doesn’t.
 The diversity that meiosis brings increases the
chances of survival of the species in an every
changing climate.
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Meiosis –
a Review
 MEIOSIS - MADE SUPER EASY – ANIMATION
 Meiosis: The Great Divide
 Chromosome Numbers During Division:
Demystified!
 Meiosis! (Mr. W's Music Video)
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Recap
Asexual
Reproduction
Sexual
Reproduction
 Mitosis
 Meiosis
 Used for growth and
repair.
 Used to survive a changing
environment.
 One cell makes two cells
that are completely and
totally the same.
 One cell makes four
completely different cells.
 Variety is key.
 Being the same matters.
 Happens in gametes
 Happens in somatic cells
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???
 If you watched the video recaps for mitosis and
meiosis, they brought up chromosomes quite a bit.
 Here’s why.
 If our little plant cells are going to survive a
changing climate, the part of the cell that can ‘adapt’
is the DNA.
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Chromosomes
 DNA, which is a nucleic acid, is a very long
molecule.
 So you need to be able to package it in a way that it
can fit inside a teeny tiny little nucleus.
 DNA is double stranded (made up of two strands),
and forms a helix (twists).
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Chromosomes
 The DNA can further twist around proteins called
nucleosomes such as the protein histone.
 DNA is now in a supercoil and it can now be called
chromatin.
 Basically, DNA takes up even less space.
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Chromosomes
 When a cell is just living and has no interest in
reproducing either asexually or sexually, you will
find all of its DNA in the form of chromatin.
 Only during mitosis and meiosis will the DNA
super-coil even further into a chromatid.
 We refer to the number of chromatids as ‘n.’
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Chromosomes
 When a cell needs to reproduce, it will make a copy of
each of their chromatids during the S phase of Interphase
in the Cell Cycle of mitosis or meiosis.
 Since you have two identical copies of each chromatid,
you need to keep them organized.
 A centromere kind of acts as a molecular paperclip by
holding together both identical copies of the chromatids.
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Chromosome
 Two identical chromatids joined together by a
centromere is what we call a chromosome.
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What makes DNA so
special?
 If you look at the structure of DNA, you will recall
that it is a nucleic acid made up of a small repeating
unit called a nucleotide.
 Each nucleotide is made up of a sugar, a phosphate,
and a nitrogenous base.
 Unwinding the DNA shows us that there is a
sugar/phosphates backbone to the DNA.
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What makes DNA so
special?
 In the middle of the two sugar/phosphate backbone
strands, we find nitrogenous bases.
 The four nitrogen bases are:- A for adenine, T for
thymine, C for cytosine, and G for guanine.
 A always pairs up with T and C always pairs up
with G = base-pairing rule.
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What makes DNA so
special?
 The order of A’s, T’s, C’s, and G’s turns out to be
really important.
 This DNA sequence, pattern, or code actually means
something.
 We call these meaningful codes genes.
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What makes DNA so
special?
 It’s these genes that help code for the making of all
of those proteins, enzymes, cell parts,… that help
make a cell work.
 If you alter any part of a gene code, you wind up
with a genetic mutation.
 A variety of things can cause a genetic mutation.
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What makes DNA so
special?
 Before we go into what happens when the genetic
code mutates, we should probably review the
structure of DNA and of a chromosome.
 It isn’t until we truly understand this bit that we can
talk about how cells and organisms can survive a
changing environment such as climate change.
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Chromosome –
a Review
 DNA Structure and Function
 What is DNA and How Does it Work?
 How DNA is Packaged (Advanced)
 Genes vs. DNA vs. Chromosomes - Instant Egghead
#19
 DNA Structure
 The Structure of DNA
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DNA Binge watching
 DNA - Episode 1 of 5: The Secret of Life - PBS
Documentary
 DNA - Episode 2 of 5 - Playing.God - PBS Documentary
 DNA - Episode 3 of 5 - The Human Race - PBS
Documentary
 DNA - Episode 4 of 5 - Curing.Cancer - PBS
Documentary
 DNA - Episode 5 of 5 - Pandora's Box - PBS
Documentary
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Recap
 We’ve discussed why it’s beneficial to have asexual
and sexual reproduction for the health of a cell or
organism.
 We discussed the Cell Cycle, Mitosis, and Meiosis.
 We discussed the structure of DNA and of
chromosomes.
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Recap
 We introduced the idea of genes and what they
code for.
 We introduced the idea that genetic mutations
change the genetic code.
 These mutations may be helpful or harmful to the
cell or organism.
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Coming up
 In the next Power Point, we will discuss our little
plant cells that were reacting to a change in the
climate and how genetic mutations may actually be
beneficial to them.
 We will also talk about how to make predictions
regarding what future generations of cells may look
like or how they may function.
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The End
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