Today is Friday (!), November 4th, 2011 Pre-Class: (it’s a simple one) Where do cells come from? Because they don’t come from this ----------> http://animalsneedkisses.files.wordpress.com/2009/03/teenage_....jpg Today’s Topics • Chromosomes • Chromosomes • And maybe strawberries… • Where is this in my book? – P. 244 and following… – Also P. 341 and following… http://www.toppstraders.org/blog/wp-content/uploads/2008/02/darryl-strawberry.jpg What a cell wants, what a cell needs… • So what exactly does a cell need? • Imagine a cell has just been “born.” – What do you suppose is most important? – What organic molecule would you pick? Of course, DNA! • DNA is the information of a cell. – The “genetic code” • This needs to be copied over to the new cell. – This stuff “codes for proteins” (like a script) and makes you who you are. DNA in pop Not what DNA actually looks culture? like… http://static.guim.co.uk/sys-images/Film/Pix/pictures/2008/06/30/jurassicpark460.jpg http://www.eyeondna.com/wp-content/uploads/2007/11/mrdna.jpg Cell Division and DNA • There are three major methods for cell division: – Binary Fission Mainly Prokaryotes Momentarily… – Mitosis Next week Eukaryotes – Meiosis Cell Division in Prokaryotes • Called “Binary Fission.” – Simple • Ring of DNA copies. • New membrane grows across the cell, pinching it “like a long balloon squeezed in the middle.” – Holt: Biology – 2 cells result, both with the same DNA • Unless something happened. Binary Fission: A View Animated Form http://upload.wikimedia.org/wikipedia/commons/d/d2/Binary_fission_anim.gif Eukaryotic Cell Division • For eukaryotes, things are different. We don’t just have DNA. Eukaryotes have… – Begins with a “C…” – Ends in a “hromatin…” • Right, eukaryotes have chromatin: http://www.reading.ac.uk/cellmigration/chromatin.jpg Chromatin • Chromatin is made of two things: – DNA – Proteins (called histones) • The DNA is wrapped around the histones. What chromatin does… • Chromatin in the nucleus is a lot like a bunch of loose fishing line. – It’s a bunch of long, thin, invisible strands. http://thumb1.shutterstock.com.edgesuite.net/display_pic_with_logo/7096/7096,1231099264,4/stock-photo-a-spool-of-monofilament-fishing- line-macro-shot-showing-all-the-dirt-and-lint-all-over-the-strands-22762768.jpg But then… • When pieces of chromatin condense, they becomes visible under the microscope. – The condensed chromatin pieces are now called chromosomes. http://www.koifishcareinformation.com/wp-content/uploads/2010/02/fishing-line-pond-protection-for-koi.jpg How big are we talkin’? • http://learn.genetics.utah.edu/content/begin/ cells/scale/ Humans • We have 46 total chromosomes (per cell). – Arranged in 23 pairs. – One chromosome in each pair is from your mother, one is from your father. • These are called homologous chromosomes. • Diploid – Diploid is an arrangement where you have pairs of chromosomes. – We describe diploid chromosome arrangements with the term 2n. Chromosomes: A Diagram View From Mom From Dad Homologous Chromosomes http://www.macroevolution.net/images/sister-chromatids-275.jpg Chromosomes: A “Real” View Other Organisms • 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 Mule • Horse + Donkey http://cloud.equinenow.com/140171_1/mare_mule_horse.jpg Liger • ♂ Lion, ♀ Tiger http://2.bp.blogspot.com/__jinAaXs1i4/TGzaZyBwtmI/AAAAAAAAAI8/bMYSAFod7bw/s640/Liger4.jpg Tiglon • ♂ Tiger, ♀ Lion http://www.metrolic.com/wp-content/uploads/2010/09/Tiglon20.jpg Zedonk • Donkey/Zebra http://4.bp.blogspot.com/_p5mAt9Tofmg/TFf_sh1ENTI/AAAAAAAAAt4/ZM0AlU4z9gU/s320/zedonk+trimmed.jpg Okapi • NOT a hybrid! (related to giraffes) http://upload.wikimedia.org/wikipedia/commons/1/18/Okapi2.jpg Karyotyping • Arranging/looking at/analyzing chromosomes is a called making a karyotype (or karyotyping). • Chromosomes are arranged primarily by size and homologous chromosomes are paired. http://www.genomenewsnetwork.org/gnn_images/whats_a_genome/karyotype.gif Two Types of Chromosomes • Autosomes – The 22 “body” chromosomes. – They’re responsible for non-gender things in the body. Two Types of Chromosomes • Sex chromosomes – The one pair of chromosomes that contains information linked to gender. • And some stuff not linked to gender. • Two X chromosomes = XX – Female • One X, One Y = XY – Male • Y chromosome is relatively small. Let’s do some karyotyping… • Visit this website: • http://learn.genetics.utah.edu/content/begin/traits/karyot ype/ • You will first just practice karyotyping on this website. • When you are finished, LEAVE YOUR COMPUTERS OUT. – We’re going to discuss some chromosome-based diseases. Sex Chromosome-Linked Conditions • XX - ♀ • XY - ♂ • XXX - Trisomy X – Female, otherwise healthy. • XXY - Klinefelter’s Syndrome – Male, reduced sex characteristics, some female characteristics. • XO - Turner’s Syndrome – Female, appear normal but sterile. Aneuploidy • An abnormal number of chromosomes is called aneuploidy. – Trisomy X, Klinefelter’s, and Turner’s are all aneuploidies, as are the conditions we will discuss on the next slides. – Aneuploidies can be autosomal or sex chromosome-linked. Autosomal Conditions • Trisomy 21 – Three copies of the 21st chromosome instead of two. – 47 total chromosomes instead of 46. – Leads to Down’s Syndrome. http://kittymowmow.files.wordpress.com/2008/01/whitetigerdeformed1.jpg Autosomal Conditions • Trisomy 13 – Three copies of the 13th chromosome instead of two. – 47 total chromosomes instead of 46. – Leads to Patau Syndrome. http://www.diagnosticpathology.org/content/figures/1746-1596-2-48-1.jpg http://myummah.co.za/site/wp-content/uploads/2009/02/image-801.jpg Let’s do some more karyotyping… • Now visit Quia and open the quiz called “Karyotyping” and follow the directions. – You’ll need a different website for the second activity. • On this website, just click where the match should go. No dragging. – Linked on my website under University of Arizona – Karyotyping. • http://www.biology.arizona.edu/human_bio/activities/ karyotyping/karyotyping.html Gametes • In autosomal cells, there are 23 pairs of chromosomes, including one pair of sex chromosomes. – You’ve probably already written this. • In sperm and egg cells (gametes), there are only 23 chromosomes total. – Haploid. – Only one sex chromosome. – 1n Gametes Egg and Sperm Cells • Egg cells are produced by females. – Made by cells that have XX karyotype. – Therefore, eggs always have one X sex chromosome. • Sperm cells are produced by males. – Made by cells that have XY karyotype. – Therefore, sperm could have either one X or one Y sex chromosome. Class Baby Pictures • And now, let’s take a look at some class baby pictures. – Seriously. – And please thank your parents for cooperating (and keeping this a secret). Zygote • Your first diploid cell: http://www.alphascientists.org/images/uploads/images/Zygote_1.jpg Gametes • Sperm and egg cells (each haploid) combine to form a zygote (first cell - diploid). – 23 chromosomes from egg + 23 chromosomes from sperm = 46 chromosomes in zygote. http://images-cdn01.associatedcontent.com/image/A6498/649888/150_649888.jpg http://www.ncbi.nlm.nih.gov/bookshelf/picrender.fcgi?book=cell&part=A5406&blobname=ch20f4.jpg Henry the VIII I even • Six wives. look like I’m an • Really wanted a son. idiot. • Whose fault was it? Eukaryotic Cell Division Preview • The rest of this unit will be discussing how eukaryotes divide. • As we said, this process is more complicated than for prokaryotes. • We’re going to wrap today up with a preview of what’s to come next week. Eukaryotic Cell Division Preview • Step 1: Chromatin/DNA must be copied • Step 2: Chromatin/DNA condenses to form chromosomes • Step 3: Chromosomes, one from Mom and one from Dad, pair up • Step 4: Copies joined by centromere • Step 5: Chromatids separate as the cell splits into two new cells Exit Ticket • Exit Ticket: Humans have ___ total chromosomes, or ___ pairs of chromosomes. • You must show me your answer on your way out the door.
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