In This Lesson:
Unit 4
Chromosomes
and Gametes
(Lesson 1 of 3)
Today is Friday (!),
November 6th, 2015
Pre-Class:
(it’s a simple one)
Where do cells come
from?
P.S. Get a paper towel.
Because they don’t come from this ---------->
http://animalsneedkisses.files.wordpress.com/2009/03/teenage_....jpg
Today’s Agenda
• Chromosomes
• Chromosomes
• And maybe strawberries…
• Where is this in my book?
– Academic: P. 244 and
following and P. 341 and
following…
– Honors: P. 126 and following…
http://www.toppstraders.org/blog/wp-content/uploads/2008/02/...ry.jpg
By the end of this lesson…
• You should be able to name the number of
human chromosomes as well as describe their
basic roles in determining gender and other
characteristics.
• You should be able to describe the properties
of human reproductive cells in terms of
genetic material.
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?
– Hint: It’s going to need to guide the cell…
Of course, DNA!
• DNA is the information of a cell – the genetic
code.
• It 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
culture?
Not what DNA
actually looks
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
Momentarily…
Prokaryotes
– Mitosis
Eukaryotes
Soon
– Meiosis
Binary Fission: A View
Animated Form
http://upload.wikimedia.org/wikipedia/commons/d/d2/Binary_fission_anim.gif
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.
Eukaryotic Cell Division
• For eukaryotes, things are different. For one,
we have a nucleus, which just complicates
things.
• Also, we don’t just have DNA, and it’s not
circular. Eukaryotes have…
– Begins with a “C…”
– Ends in a “hromatin…”
• Right, eukaryotes have chromatin:
• Video!
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-fishingline-macro-shot-showing-all-the-dirt-and-lint-all-over-the-strands-22762768.jpg
But then…
• When pieces of chromatin condense, they
become visible under the microscope.
– The condensed chromatin pieces are now called
chromosomes.
• Trivia: Called chromosomes because they absorb dye
easily.
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/
• Scale of the Universe
Humans
• We have 46 total
chromosomes (in each cell).
– Arranged in 23 pairs – 2 copies
of each.
– One chromosome in each pair
is from your mother, one is
from your father.
• These are called homologous
chromosomes.
– They may not be exactly the
same, but they carry the same
types of information.
• Like eye color, perhaps.
Mom
1.
2.
3.
.
.
.
.
.
.
23.
Dad
Humans
• Our body cells have a diploid arrangement of
chromosomes.
– Diploid is word that describes an arrangement in
which you have pairs of chromosomes.
– We describe diploid chromosome arrangements with
the term 2n.
• n = how many chromosome types we have.
• In humans, n = 23. 2(23) = 46 total chromosomes.
– Example: A pair of shoes is much like a pair of
chromosomes in a diploid arrangement. Same shoe,
but slightly different (left vs. right).
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
• Oxytricha trifallax (protozoan): ~16,000
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
Platypus (also not a hybrid)
• Monotreme (egg-laying mammal) with 10 sex
chromosomes and DNA features characteristic of
mammals, birds, and reptiles (!).
http://1.bp.blogspot.com/-2zq5eXFKk5E/Tc6GeJUi5fI/AAAAAAAAAro/ad_I1NKNF8c/s1600/Platypus+003.jpg
Karyotyping
• Arranging/looking at/analyzing chromosomes is
called making a karyotype (or karyotyping).
• Chromosomes are arranged primarily by size and
homologous chromosomes are paired.
• The term karyotype
can also be used to
describe the number
or type of
chromosomes in a
cell.
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.
X and Y Chromosomes?
• The X chromosome is
much larger than the Y.
• X carries a lot of genes
(140 to be exact), some
related to gender, some
not.
• Y carries only about 40
genes and nearly all are
related to being a male.
So what’s on those chromosomes?
• Human Chromosome Map
• Human Chromosome Map Pictures
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. (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)
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 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
You may be thinking…
• If an extra chromosome copy is so harmful,
how are females not harmed by having two Xchromosomes? Don’t they have the same
information?
– While females do have two X chromosomes, one
of the two is randomly inactivated early in
development (prior to pregnancy).
– The chromosome that is turned off is called a Barr
Body.
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 this activity.
• On this website, just click where the match should go.
No dragging.
– Linked on my website under University of Arizona
– Karyotyping or in the quiz itself.
• http://www.biology.arizona.edu/human_bio/activities/
karyotyping/karyotyping.html
• You’re going to be diagnosing people with
chromosomal diseases (or nothing).
Gametes
• In somatic cells (non-sex cells),
1.
there are 23 pairs of
2.
chromosomes, including one pair
3.
of sex chromosomes.
– You’ve probably already written
most of this – just take note of the
definition of “somatic cells.”
• In sperm and ova (gametes), there
are only 23 chromosomes total.
– Haploid (1n).
– Only one sex chromosome.
– Like having only a left shoe instead
of a pair of shoes.
.
.
.
.
.
.
23.
Somatic
Gametes
Cells
Gametes
Ova and Sperm
• Ova (eggs) are produced by females.
– Made by cells that have XX karyotype.
– Therefore, ova 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
• One sperm and one ovum (each haploid)
combine to form a zygote (first cell - diploid).
– 23 chromosomes from egg + 23 chromosomes from
sperm = 46 chromosomes in zygote.
– Like matching a left shoe (sperm) with a right shoe
(ovum).
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
• Six wives.
• Really wanted a son.
• Whose “fault” was it?
I even
look like
I’m an
idiot.
Exit Ticket
• Exit Ticket: Humans have ___ total chromosomes, or
___ pairs of chromosomes.
• You must show me your answer on your way out the
door.