Introduction to Meiosis
Mr. Nichols
PHHS
Introduction to Meiosis
 Only occurs in egg and sperm cells.
 Results in 4 daughter cells.
 Each daughter cell is genetically different.
 Each daughter cell has 23 chromosomes.
 Recall our mystery from today: The odds of your parents
conceiving a child genetically identical to is 1: 4,500,000,000
(4.5 Billion), how do sperm and egg make this possible?
Here’s your task
 You are your group mates are genetic engineers who are creating a
new species of elephant.
 It’s clear to you that you want this new species to have sex cells
very similar to that of humans.
 Problem: With the new information you have about meiosis,
purpose a way in which these elephants can produce 4 genetically
different sperm/eggs.
 Note: Do your best, this is meant to be difficult.
Hint #1
 Start- One cell
 Finish- 4 daughter cells that are genetically different than the
original.
Hint #2
 Start- One cell
 Half way- Two genetically different cells with 46 chromosomes.
 Finish- 4 daughter cells that are genetically different than the
original.
Answer!
 Meiosis is simply Mitosis done twice, with one slight modification.
 Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis- 2 cells
Finished!!!!
Meiosis
Interphase
Prophase I
Metaphase I
Anaphase I
Telophase I
Cytokinesis- 2 cells
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis- 4 cells
Finished!!!!
Prophase I- How is it different?
 Crossing over- During Prophases 1, now visible
chromosomes exchange genetic information with one
another.
Chromosome Summary
Comparison Time
 Mitosis vs. Meiosis T Chart
Strange Animal Mating Behaviors
 Human Mating Behaviors are often complicated and full of
‘drama,’ but we definitely aren’t the only ones.
 Top 10 Strange Animal Mating Behaviors and Sex Facts.
 Warning: The word ‘Penis,’ will be used!
Number 10- Exploding Testicles
 A virgin queen that survives to adulthood without being killed
by her rivals will take a mating flight with a dozen or so male
drones (out of tens of thousands eligible bachelors in the
colony). But don’t call these drones lucky because during
mating, their genitals explode and snap off inside the queen!
 Strange as it is, this actually makes evolutionary sense: the
snapped-off penis acts as a genital plug to prevent other
drones from fertilizing the queen. But tell that to the dead
drone whose penis just exploded.
Number 9- Make Love Not War
 Who said that violence is the only way to solve fights over
food or territory? Instead of fighting, bonobos have sex!
Actually, their whole societal structure seems to revolve
around sex.
 Bonobos use sex as greetings, a mean of solving disputes,
making up for fights, and as a favors in exchange for food.
They tongue kiss, engage in oral sex, mutual masturbations,
have face-to-face genital sex and even have a strange "penis
fencing" ritual!
Number 8- Definitely not Flipper
 Here’s something you probably don’t know about Flipper: he has
retractable penis. And if that’s not cool enough, here’s something
else: his penis is prehensile. And it swivels. In fact, a male
dolphin can use his penis to explore objects just like a hand.
 Male dolphins also have a very strong sex drive. It can mate
many, many times in a day. Now here’s the bad news: male
dolphins aren’t that much of a stud. The average time to
ejaculation? 12 seconds.
 Another hushed-up fact is that male dolphins have a ravenous
sexual appetite: they often try to hump inanimate objects and
even other animals like sea turtles. When a pack of male
dolphins happen upon a female, often times they will attempt to
force her to mate.
Number 7- Your mom is your dad
 Clownfish live in a group consisting of a breeding pair of male
and female, as well as some non-breeding males. There is
strict hierarchy based on size: the largest is the female, next
largest is the male, and then the non-breeding males.
 If the female dies (or gets fished, I suppose), the male will
change sex and become the female! Then the largest of the
non-breeding males will get a promotion to become the
breeding male.
Number 6- Slow and Spiny wins
the race
 Snails’ genitals are on their necks, right behind their eyestalks. Not weird enough?
 Snails are hermaphrodites, meaning they have both male
and female sexual organs, but they do not self-fertilize.
 Before two snails mate, they shoot "love darts" made of
calcium at each other. People used to think that these sharp
darts are nutritional gifts, like you give someone you love a
box of chocolate
Number 5- Don’t let the bed bugs
bite
 Here’s chivalry for you: the male bedbugs don’t even bother
with the female’s sex organs. Instead, a male bedbug uses
its scimitar-like sexual organ to impale the female bedbug’s
body and deposit his sperm!
 Scientists even have a cute name for this sort of thing:
"traumatic insemination." Ouch!
Number 4- Porcupines!!!
 First of all, female porcupines are interested in sex only
about 8 to 12 hours in a year! Second, to court a female
during the short mating season, a male porcupine stands up
on his hind legs, waddles up to her, and then sprays her with
a huge stream of urine from as far as 6 feet away, and
drench his would-be paramour from head to foot!
 If the female wasn’t impressed, she’ll scream and shake off
the urine. But, if she is ready, then she’ll rear up to expose
her quill-less underbelly. Once mating begins, the female is
insatiable: she forces the male to mate many times until he is
thoroughly exhausted. If he gets tired too quickly, she will
leave him for another male!
Number 3- She wore Red Velvet
 Red velvet mite, which is as big as one of the letters in this
sentence, has a peculiar mating habit.
 The male releases its sperms on small twigs or stalks in what
scientists call the "love garden", then lays down an intricate
silken trail to the spot. When a female stumbles upon this
trail, she will follow it to seek out the "artist". If she likes his
work, then she will sit on the sperm.
 However, if another male spots the garden, he will trash it
and lay his own instead!
Number 2- Not Bubble Gum
 The average size of a banana slug penis is 6 to 8 inches.
This is incredibly impressive, considering their entire body
length is 6 to 8 inches as well!
 Banana slugs are hermaphrodites, so two slugs will try to
fertilize each other. To mate properly, a slug must choose a
mate roughly its own size – if it miscalculates, its penis will
get stuck during copulation.
 This isn’t just an embarrassing faux pas, the other slug will
actually bite off the stuck penis, a term scientists
euphemistically called "apophallation."
Number 1- Magical Lasso
 The Argentine lake duck may be small, but don’t take pity on it. See,
the drake (male duck) of the lowly fowl has the longest penis of any
bird species in the world.
 From head to tail, the Argentine lake duck measures about 17 inches.
That also happens to be the length of its corkscrew-shaped penis
when stretched out. The tip of the penis is soft and brush-like, which
the drake uses to brush away sperms deposited by a previous suitor.
 University of Alaska Kevin McCracken explains that the ducks are
promiscuous, and the long penis may be an evolutionary adaptation for
the males to become more attractive to the females. That, and the
drake also uses his penis to "lasso" a female who tries to escape from
it.
Cartoon of the Day!
Mystery for Today
 The odds of your parents conceiving a child genetically
identical to is 1: 4,500,000,000 (4.5 Billion), how do sperm
and egg make this possible?
Feedback from last week!
 Some things I noticed:
 1.) Varying levels of comfort with the steps in Mitosis.
 2.) Some were unsure with Telophase and Cytokinesis
 Some things to go over again:
 1.) More detail on the G1 and G2 checkpoints.
 2.) Where do the spindle fibers come from?
 3.) Do some cells undergo Mitosis faster and why?
 4.) How does the nuclear envelope dissolve?
 5.) Why do cells divide?
 6.) When and why does the cell grow?
 7.) Do all cells go through Mitosis?
 8.) How are organelles reproduced?
 9.) How do cells detect problems in the checkpoints?
 10.) How does a cell divide after its already divided?
G1 and G2 checkpoints
 A protein called p53 checks the structure of the DNA molecule to
make sure common mutations have not occurred, if it finds errors,
two mechanisms are triggered:
 1.) p53 triggers cell ‘apoptosis,’ which causes the cell’s mitochondria
lose their functionality and to take on toxic levels of calcium from the
surrounding environment.
 2.) The cell sends a message to Macrophages (large immune cells)
that they need to be destroyed. This message is given via a cytokine
(protein) called TNF.
Spindle Fiber Formation
 Spindle fibers are made mostly of cytoskeletal microtubules.
 In early Prophase a protein called katanin comes in and cuts
some microtubules into spindle like structures.
 These spindle fibers are then organized and attached to ‘motor
protein,’ (kinesin and dynein) to move chromosomes during
metaphase.
Characteristics of Mitosis
 4 Phases (PMAT)
 Produces 2 genetically identical cells.
 Each daughter cell has 46 chromosomes.
 Daughter cells do not completely split until after Mitosis (cytokinesis)
 Only occurs in Non-Sex Cells. (everything but egg and sperm)
Meiosis
Mr. Nichols
PHHS
Lab Report
Introduction: What, why, how? Be Brief.
Hypothesis: State your hypothesis.
Data/Results: Tabularize and Graph ALL DATA (All Partners)
Conclusion: Answer these questions- Which muscle group
exerts the most force (use data to support)? Offer an explanation as to why
this muscle is strongest. Which muscle type (smooth, skeletal, cardiac)
exerts the most force? Offer an explanation. What parts of the experiment
clearly demonstrated muscle fatigue, how do muscles get tired? Offer and
explanation.
Discussion: What experiment could you do with given what you know now
to discover more knowledge? Name a minimum of three sources of error
and how you would correct them if you conducted this lab again.
Question of the Day!
AT
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GC
CG
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Introduction to Meiosis
 The real story behind how babies are made.