In This Lesson: Unit 5 Mitosis and the Cell Cycle (Lesson 1 of 3)

Today is Wednesday, November 30th, 2016

Pre-Class: From where do cells originate? Because they don’t come from this: 

P.S. Have your Guided Reading on your desks. http://animalsneedkisses.files.wordpress.com/2009/03/teenage_....jpg

Today’s Agenda • Chromosome basics. • The Cell Cycle. • Mitosis. – Where division = multiplication.

• But first… – Class baby pictures. Yes, you.

• Where is this in my book? – Chapter 12.

By the end of this lesson… • You should be able to describe a normallyfunctioning somatic cell cycle and analyze what would happen if it no longer functioned properly. • You should be able to identify several chromosomal diseases using karyotypes. • You should be able to contrast mitosis and binary fission.

A Rather Striking Introduction • i am so proud of you – Don Hertzfeldt

Class Baby Pictures • On the next slide, I have photos of some of you as wee lil’ babies. – Maybe not all, but at least some.

• Please thank your parents for keeping it a secret. – They did keep it a secret, right?

• Let’s see…who’s up first…?

You. • It’s your first diploid cell. The zygote. You all started this way. – You’ve come a long way.

http://www.alphascientists.org/images/uploads/images/Zygote_1.jpg

Okay then… • …let’s get to some Challenge Questions.

The Cell Theory • Think back to the cell theory… – All living things are made of cells. – Cells are the basic units of structure and function. – All cells come from preexisting cells.

• That last one is the big one for us right now.

You again. • You started as a microscopic single cell – a zygote, the cell that resulted from the fusion of gametes – far smaller than the period at the end of this sentence.

Aw, you were so cute then…

Since then… • From that point forward, you’ve been dividing and dividing your cells. – Remember, that’s all you are. Just a bunch of overgrown zygotes.

• Now you’re a trillion-celled living, breathing, thinking emoting human being with a cell phone addiction.

Why Divide? • Growth is just one reason. Cells also divide for • Reproduction if they’re unicellular. If they’re part of a multicellular organism, they may divide for • Repair or renewal, such as when a cut heals or • Differentiation, since they need to grow up and get jobs. • Not to mention, cells also have to divide because they really can’t get bigger without ruining that whole surface area-to-volume ratio.

So what do we need to know? • To fully understand the cellular division process, which itself is mostly review of what you’ve already learned, we need to understand the following: – Chromosomes • Hey, how do you pronounce that? Dialect Survey!

– Karyotyping – The Cell Cycle

Chromosomes [Review] • Recall that humans have 46 chromosomes arranged in 23 pairs in each of their somatic cells, of which 22 pairs are considered autosomes. – Somatic cells are body cells, as in “not reproductive cells.” • Any cell that’s not sperm/egg.

– Autosomes are “body chromosomes” – they don’t directly have anything to do with sex characteristics. • Any chromosome that’s not a sex chromosome.

• One pair of chromosomes is the sex chromosomes. – Female = XX; male = XY.

Chromosomes [Review] • Humans have 46 chromosomes in 23 pairs. – This is a diploid arrangement, also given by the designation 2n – we have 23 chromosomes with 2 copies of each. – Each chromosome in a pair (homologous chromosomes) is similar to the other, one carrying info from mom and one carrying info from dad. • It’s like having a pair of shoes. You need both and they are different, but they’re still mostly the same.

Chromosomes [Review] • Gametes are reproductive cells (such as sperm/ova), and they have a 1n (haploid) arrangement. – Each gamete provides half the BFF necklace/chromosomes needed for a full somatic cell. – When they fuse, the two gametes form a zygote.

Diploid and Haploid Somatic Cells Mom 1. 2. 3. . . . . . . 23.

Gametes

Dad

Diploid Arrangement

Homologous Chromosomes

1. 2. 3. . . . . . . 23. Haploid Arrangement

Chromosomes • • • •

Dog: 78 Chromosomes (39 pairs) Orangutan: 48 Chromosomes (24 pairs) Mouse: 40 Chromosomes (20 pairs) Strawberry: 56 Chromosomes (7 groups of 8 octoploid) • Adders-tongue fern: 1200 or 1260 Chromosomes • Oxytricha trifallax (protozoan): ~16,000 chromosomes

Chromosomes [Review] • The X chromosome is rather large and has between 800 and 900 genes. – They’re not particularly female-related. • Colorblindness and hemophilia are linked to X-chromosome genes, for example.

• The Y chromosome only has about 40 genes. – They’re called holandric genes, by the way.

• Therefore, if you inherit a combination of X or Y genes different from XX or XY, interesting changes occur.

Chromosomes [Review] • XXX – Trisomy X – Female, otherwise healthy. (1 in 1000 females)

• XXY – Klinefelter Syndrome – Male, reduced sex characteristics, some female characteristics.

• X0 – Turner Syndrome – Female, appear normal but sterile.

• XYY – Male, otherwise healthy. (1 in 1000 males)

Chromosomes [Review] • Chromosomes are often studied in a karyotype. – A karyotype is either: • A photo/diagram showing all the chromosomes of an organism/individual, OR • The actual chromosomes present in the cell of an organism/individual.

• Let’s take a look at some…

Karyotypes • Human Male

http://kennethtls.blogspot.com/2010/11/gender-crisis.html

Karyotypes • Human Female – Turner Syndrome

http://kennethtls.blogspot.com/2010/11/gender-crisis.html

Karyotypes • Human Male – Klinefelter Syndrome

http://kennethtls.blogspot.com/2010/11/gender-crisis.html

Other Chromosomal Diseases • Any case of an abnormal chromosome number is called aneuploidy. • For example: – Three copies of chromosome 21? • Down Syndrome (Trisomy 21)

– Three copies of chromosome 13? • Patau Syndrome

– Two copies of chromosome X? • Female…no, really, this one’s interesting.

Females • If males can survive with only one X chromosomes, how come females don’t suffer problems with two copies? • Turns out, in females, a single X chromosome in each cell is randomly inactivated shortly after conception. • The inactivated X chromosome is called a Barr body. – Remember this for a cool fact later. We’ll also talk about how all these aneuploid issues arise.

From females to…bacteria? • For most of the rest of this PowerPoint we’re going to be discussing eukaryotic somatic cell division (mitosis), but we do need to get something out of the way first: – Binary fission.

• Binary fission is prokaryotic cell division and it’s pretty simple: – Copy DNA. • They only have a single, circular, folded-up DNA molecule.

– Divide.

Binary Fission

Back to Chromosomes [Review] • Chromosomes are only visible during mitosis. • During other parts of the cell cycle, they’re invisible to a light microscope in a form known as chromatin. – Chromatin is simply DNA wrapped around spherical proteins known as histones. – The histone/DNA complex is known as a nucleosome. https://www.broadinstitute.org/files/news/images/2010/chromatin_states_2a.png

histone

And speaking of the cell cycle… • The Cell Cycle consists of these stages: • G1 – Gap 1 (growth phase).

• S – Synthesis (DNA is copied).

• G2

– Gap 2 (growth phase). – New organelles are made.

• M – Mitosis (nucleus divides).

• Cytokinesis – Cytoplasm divides.

The Cell Cycle [Review] • There’s also a bonus stage called G0. – That’s pronounced “G naught.”

• Cells in G0 do not divide by mitosis, like brain cells and some muscle cells. – G0 is thus not part of the cell cycle.

M Mitosis G2 Gap 2

S Synthesis

G1 Gap 1

G0 Resting

The Cell Cycle [Review] • G1, S, and G2 together make up interphase, the collective name for the “resting phase.” – “Resting phase” is a bad name.

• The nucleus is present and easy to spot. – DNA is in the form of chromatin.

The Cell Cycle [Review] • During S phase, all six feet of DNA needs to be copied. – Error rate in copying? 1 in 100 million DNA bases. – With ~30 billion bases in the mammalian genome, that’s around 30 errors each cycle. • Not evolution – these are body cells.

Terminology [Review] • We’re almost there. • Before we get into M phase details, there’s one last thing to talk about – chromosome terminology. – It’s gonna get complicated in hurr…

Terminology [Review]

S Phase Chromosomes are copied Sister Sister Chromosome Chromosome Chromatid Chromatid

Pre-S Phase

Post-S Phase

Terminology [Review] • Chromatid – Half of a duplicated (X-shaped) chromosome. – Prior to duplication, it was called a chromosome.

• Sister Chromatids – The two identical chromatid copies that make up an Xshaped chromosome.

• Centromere – The site at which the two sister chromatids join. • It’s really just a stretch of DNA, so it’s there before and after S phase (DNA duplication).

– Basically the same as the kinetochore – where spindle fibers (later) will attach.

Terminology [Review] Sketch me!

Sketch me!

Sketch me!

Sketch me!

Sketch me!

Sketch me!

http://www.janewhitney.com/img/sister_chromatids.jpg

Phew. Time for Mitosis. • Key organelles in mitosis: – Nucleus (duh) – Centrioles • Aid in cell division, remember? • Something new: Centrioles are found in a region of the cell known as the centrosome. • There is one centrosome for each of the two pairs of centrioles.

Mitosis [Review] • What it looks like:

http://royaleb.files.wordpress.com/2009/04/mitosis_phases1.jpg

Mitosis [Review] • What it kinda looks like:

http://www.geekosystem.com/wp-content/uploads/2010/07/donut-mitosis.jpeg

Mitosis [Review] • What it doesn’t look like:

http://icanhascheezburger.files.wordpress.com/2008/03/funny-pictures-mitosis-rabbits.jpg

Mitosis [Review] • Mitosis (M phase) is the division of the nucleus. • There are four main phases of mitosis: – Prophase • Some people put an additional step here: Prometaphase.

– Metaphase – Anaphase – Telophase

• Got a way to remember these?

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/early_late_prophase1_pc.jpg

Prophase [Review] • Chromatin condenses into chromosomes. – Chromosomes have been copied by now and look like little X’s.

• Nuclear membrane/nucleolus breaks down. • Mitotic spindle fibers (the “ropes”) form. – The spindle fibers are made of microtubules (actin/myosin).

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/prophase.gif

Prometaphase • Prometaphase is an intermediate step between Prophase and Metaphase (obvious). – Starts when the nucleus breaks down, centrioles have moved apart, and spindle fibers are forming and hooking onto the chromosomes. • This centromere/spindle structure is called a kinetochore.

– Ends when the chromosomes are being moved into the center of the cell.

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/metaphase1_ac.jpg

Metaphase [Review] • Chromosomes line up in the middle of the cell at the metaphase plate. – Sometimes called the equator.

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/metaphase.gif

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/early_anaphase1_pc.jpg

Anaphase [Review] • Centromeres divide. – Sister chromatids are pulled apart. – Chromatids move toward the poles.

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/anaphase.gif

Anaphase: Chromosome Movement • Some really famous research was devoted to figuring out how chromosomes are brought toward the poles. – We know it’s partially with the use of motor proteins (see diagram). – Are microtubules (spindle fibers) dismantled near the centrosome or near the kinetochore? • It’s the kinetochore end that’s shortened.

• 

Aside: Spelling Counts • Don’t be my former student…

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/telophase_ac.jpg

Telophase [Review] • Nuclear envelope re-forms. • For just a little while, there are two nuclei. – These are the daughter nuclei.

• Chromosomes expand into chromatin. • Cytokinesis begins.

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/telophase.gif

http://www.bio.miami.edu/~cmallery/150/mitosis/sf8x9a.jpg

Cytokinesis in Animal Cells [Review] • The cell divides into two daughter cells. • A belt of actin microfilaments pinches the membrane together between nuclei – forms a cleavage furrow. • Cell walls are a little different (next slide).

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/cytokinesis.gif

http://wpcontent.answers.com/wikipedia/commons/thumb/5/5b/Phragmoplast.png/300px-Phragmoplast.png

Cytokinesis in Plant Cells [Review] • Cell plate forms from vesicles, which themselves form a pair of cell membranes (sent from Golgi). – Cell wall is inside the vesicle membrane.

• Cell wall forms on top of the cell plate, dividing the cell into two daughter cells.

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNArep/images/telophase2_pc.jpg

Cytokinesis in a Plant Cell

Mitosis in a Plant Cell

Mitosis in Onion Roots

Mitosis in Animal Cells

Mitosis in Whitefish

Mitosis Summary • This really cool company called Hybrid Medical Animations put together an awesome CGI look at mitosis in a cell. • http://www.hybridmedicalanimation.com/wo rk/animation/the-stages-of-mitosis/

Mitosis Scope Activity • Okay, here’s a change-of-pace. • At each of your lab tables is a microscope along with a slide showing mitosis in onion root tips. • Take a look around the slide and, with your group, see if you can spot cells in different stages of mitosis. – – – –

As I walk by, point some out to me. Make sure you all rotate in to view the scope. Hint: where on the root would mitosis be happening most? Lastly, don’t goof off. Just because there aren’t any questions doesn’t mean you can’t learn from this. • Triple negative?

Summary of Mitosis Start with one diploid cell that has 46 chromosomes.

46 Mitosis

46

End with two cells called? They each have how many Twochromosomes? diploid daughter cells each with 46 chromosomes

46

Mitosis • What it actually really looks like (see the spindles?):

http://www.geekosystem.com/wp-content/uploads/2010/07/donut-mitosis.jpeg

Mitosis Fun Facts • 300,000,000 cells die and are replaced every minute – roughly equal to the population of the United States. • 50,000,000 cells are born in the time it takes me to read this. • Nerve cells do not divide but are replaced from glial cells through neurogenesis.

Aside: How Old Are You? • While it’s true that cells divide relatively quickly, they also don’t last forever. • Right now, the oldest cells in your body are 79 years old. – That’ll stay the same throughout your life – always 7-9 years old, max, for your cells…

• …which means that nothing living about you is actually as old as…you. – Whoooooooa.

Mitosis Rap • Yep, not kidding…we’re going to listen to a mitosis rap. – I didn’t do it…could you have guessed?

Mitosis Rap Lyrics “I” is for Interphase is step 1 the step before mitosis has begun. “P” is for Prophase is step 2 the chromosome double dog that’s what they do.

“T” is for Telophase is step 5, right two daughter cells are made in both of our life…a’ight.

Mitosis tells all my cells to divide. “M” is for Metaphase is step 3 Each cells put chromosomes to the chromosomes line up as you opposite sides. can see. It makes daughter cells that are two of a kind, two of a “A” is for Anaphase is step 4 kind. as chromosomes move away from the core.

Other Mitosis Stuff • Mitosis App – https://itunes.apple.com/us/app/mitosis/id34818 4626?mt=8

• Mitosis – Phase Contrast Microscope video

Cell Division Practice • Time for a Quia quiz: Labeling Mitosis. – This one’s important!

• Leave your computer on but closed when you’re done.

Cell Cycle Game • Grab yo’ laptops and find The Cell Cycle Game: • http://nobelprize.org/educational/medicine/2001/in dex.html – Also linked from my Biology Links page – UNIT 4.

• Complete the Quia activity called Cell Cycle Game. • Keep an eye on the dial in the upper left corner and the “energy” in the upper right!

Back to the Cell Cycle • You’ve now reviewed all of the cell cycle, from interphase through mitosis and cytokinesis. – That’s the “what,” as in, “what is the cell cycle?”

• We now need to talk about the regulation of the cell cycle. – This is the “how,” as in, “how does the cell manage this whole process and keep it from getting out of control?

Cell Cycle Regulation • Imagine, for a moment, what it would be like if all cells in a bear had the same cycle? – One moment it’d just be sitting there, the next moment it would be TWICE AS HUGE.

• Normal growth and maintenance of a multicellular creature thus requires careful coordination of cell division.

Cell Division Frequency • First of all, how long does it take the average cell to divide? – Embryonic cells =