TedTest

From the Ted Talk by Leo Q. Wan: Why are human bodies asymmetrical?

Unscramble the Blue Letters

Symmetry is everywhere in nartue, and we usually associate it with beauty: a perfectly shaped leaf, or a butterfly with iantrtcie patterns mirrored on each wing. But it turns out that asymmetry is pretty important, too, and more comomn than you might think, from crabs with one giant pcienr claw to sinal sepcies whose shells' always coil in the same direction. Some species of banes only climb up their trellises clockwise, others, only counterclockwise, and even though the human body looks pttrey symmetrical on the outside, it's a different story on the inside. Most of your vital organs are arranged asymmetrically. The heart, stomach, spleen, and pcearans lie towards the left. The gallbladder and most of your liver are on the right. Even your lungs are different. The left one has two lobes, and the right one has three. The two sides of your brain look similar, but function differently. Making sure this asymmetry is distributed the right way is cciaritl. If all your internal organs are flipped, a condition caelld situs ireuvsns, it's often harmless. But iceoplmtne reversals can be fatal, especially if the heart is involved. But where does this asymmetry come from, since a brand-new embryo looks icdanietl on the right and left. One theory focuses on a small pit on the embryo called a node. The node is lined with tiny hrias called cilia, while tilt away from the head and whirl around ridpaly, all in the same direction. This synchronized rotation pushes fluid from the right side of the embryo to the left. On the node's left-hand rim, other cilia sense this fiuld flow and activate specific genes on the embryo's left side. These genes direct the cells to make certain proteins, and in just a few horus, the right and left sides of the embryo are ceahmlicly different. Even though they still look the same, these chemical differences are eventually trlteaansd into asymmetric ongras. Asymmetry shows up in the heart first. It begins as a straight tube along the center of the embryo, but when the erymbo is around three weeks old, the tube starts to bend into a c-shape and rotate towards the right side of the body. It grows different structures on each side, eventually turning into the familiar asymmetric heart. Meanwhile, the other major organs emerge from a central tube and grow towards their utlaimte positions. But some organisms, like pigs, don't have those embryonic cilia and still have asymmetric internal organs. Could all cells be intrinsically asymmetric? Probably. Bacterial colonies grow lacy branches that all curl in the same direction, and human cells cultured inside a ring-shaped boundary tend to line up like the ridges on a cruller. If we zoom in even more, we see that many of cells' biasc building blocks, like ncileuc aicds, proteins, and sugars, are ihretnnely asymmetric. Proteins have complex asymmetric shapes, and those proteins control which way cells migrate and which way ebmiyronc cilia twirl. These biomolecules have a property called chirality, which means that a mloelcue and its mirror image aren't identical. Like your right and left hands, they look the same, but trying to put your right in your left glove proves they're not. This aremstmyy at the molecular leevl is reflected in asymmetric clles, asymmetric embryos, and finally asymmetric orsinamgs. So while symmetry may be bueuftial, asymmetry holds an allure of its own, found in its grcaufel whirls, its organized complexity, and its striking imperfections.

Open Cloze

Symmetry is everywhere in ______, and we usually associate it with beauty: a perfectly shaped leaf, or a butterfly with _________ patterns mirrored on each wing. But it turns out that asymmetry is pretty important, too, and more ______ than you might think, from crabs with one giant ______ claw to _____ _______ whose shells' always coil in the same direction. Some species of _____ only climb up their trellises clockwise, others, only counterclockwise, and even though the human body looks ______ symmetrical on the outside, it's a different story on the inside. Most of your vital organs are arranged asymmetrically. The heart, stomach, spleen, and ________ lie towards the left. The gallbladder and most of your liver are on the right. Even your lungs are different. The left one has two lobes, and the right one has three. The two sides of your brain look similar, but function differently. Making sure this asymmetry is distributed the right way is ________. If all your internal organs are flipped, a condition ______ situs ________, it's often harmless. But __________ reversals can be fatal, especially if the heart is involved. But where does this asymmetry come from, since a brand-new embryo looks _________ on the right and left. One theory focuses on a small pit on the embryo called a node. The node is lined with tiny _____ called cilia, while tilt away from the head and whirl around _______, all in the same direction. This synchronized rotation pushes fluid from the right side of the embryo to the left. On the node's left-hand rim, other cilia sense this _____ flow and activate specific genes on the embryo's left side. These genes direct the cells to make certain proteins, and in just a few _____, the right and left sides of the embryo are __________ different. Even though they still look the same, these chemical differences are eventually __________ into asymmetric ______. Asymmetry shows up in the heart first. It begins as a straight tube along the center of the embryo, but when the ______ is around three weeks old, the tube starts to bend into a c-shape and rotate towards the right side of the body. It grows different structures on each side, eventually turning into the familiar asymmetric heart. Meanwhile, the other major organs emerge from a central tube and grow towards their ________ positions. But some organisms, like pigs, don't have those embryonic cilia and still have asymmetric internal organs. Could all cells be intrinsically asymmetric? Probably. Bacterial colonies grow lacy branches that all curl in the same direction, and human cells cultured inside a ring-shaped boundary tend to line up like the ridges on a cruller. If we zoom in even more, we see that many of cells' _____ building blocks, like _______ _____, proteins, and sugars, are __________ asymmetric. Proteins have complex asymmetric shapes, and those proteins control which way cells migrate and which way _________ cilia twirl. These biomolecules have a property called chirality, which means that a ________ and its mirror image aren't identical. Like your right and left hands, they look the same, but trying to put your right in your left glove proves they're not. This _________ at the molecular _____ is reflected in asymmetric _____, asymmetric embryos, and finally asymmetric _________. So while symmetry may be _________, asymmetry holds an allure of its own, found in its ________ whirls, its organized complexity, and its striking imperfections.

Solution

critical
hairs
hours
nature
incomplete
cells
molecule
organs
asymmetry
embryo
beautiful
chemically
rapidly
nucleic
intricate
pretty
ultimate
basic
translated
inherently
called
identical
pancreas
common
inversus
fluid
organisms
acids
graceful
embryonic
pincer
beans
level
snail
species

Original Text

Symmetry is everywhere in nature, and we usually associate it with beauty: a perfectly shaped leaf, or a butterfly with intricate patterns mirrored on each wing. But it turns out that asymmetry is pretty important, too, and more common than you might think, from crabs with one giant pincer claw to snail species whose shells' always coil in the same direction. Some species of beans only climb up their trellises clockwise, others, only counterclockwise, and even though the human body looks pretty symmetrical on the outside, it's a different story on the inside. Most of your vital organs are arranged asymmetrically. The heart, stomach, spleen, and pancreas lie towards the left. The gallbladder and most of your liver are on the right. Even your lungs are different. The left one has two lobes, and the right one has three. The two sides of your brain look similar, but function differently. Making sure this asymmetry is distributed the right way is critical. If all your internal organs are flipped, a condition called situs inversus, it's often harmless. But incomplete reversals can be fatal, especially if the heart is involved. But where does this asymmetry come from, since a brand-new embryo looks identical on the right and left. One theory focuses on a small pit on the embryo called a node. The node is lined with tiny hairs called cilia, while tilt away from the head and whirl around rapidly, all in the same direction. This synchronized rotation pushes fluid from the right side of the embryo to the left. On the node's left-hand rim, other cilia sense this fluid flow and activate specific genes on the embryo's left side. These genes direct the cells to make certain proteins, and in just a few hours, the right and left sides of the embryo are chemically different. Even though they still look the same, these chemical differences are eventually translated into asymmetric organs. Asymmetry shows up in the heart first. It begins as a straight tube along the center of the embryo, but when the embryo is around three weeks old, the tube starts to bend into a c-shape and rotate towards the right side of the body. It grows different structures on each side, eventually turning into the familiar asymmetric heart. Meanwhile, the other major organs emerge from a central tube and grow towards their ultimate positions. But some organisms, like pigs, don't have those embryonic cilia and still have asymmetric internal organs. Could all cells be intrinsically asymmetric? Probably. Bacterial colonies grow lacy branches that all curl in the same direction, and human cells cultured inside a ring-shaped boundary tend to line up like the ridges on a cruller. If we zoom in even more, we see that many of cells' basic building blocks, like nucleic acids, proteins, and sugars, are inherently asymmetric. Proteins have complex asymmetric shapes, and those proteins control which way cells migrate and which way embryonic cilia twirl. These biomolecules have a property called chirality, which means that a molecule and its mirror image aren't identical. Like your right and left hands, they look the same, but trying to put your right in your left glove proves they're not. This asymmetry at the molecular level is reflected in asymmetric cells, asymmetric embryos, and finally asymmetric organisms. So while symmetry may be beautiful, asymmetry holds an allure of its own, found in its graceful whirls, its organized complexity, and its striking imperfections.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
internal organs	2
embryonic cilia	2

Important Words

acids
activate
allure
arranged
associate
asymmetric
asymmetrically
asymmetry
bacterial
basic
beans
beautiful
begins
bend
biomolecules
blocks
body
boundary
brain
branches
building
butterfly
called
cells
center
central
chemical
chemically
chirality
cilia
claw
climb
clockwise
coil
colonies
common
complex
complexity
condition
control
counterclockwise
crabs
critical
cruller
cultured
curl
differences
differently
direct
direction
distributed
embryo
embryonic
embryos
emerge
eventually
familiar
fatal
finally
flipped
flow
fluid
focuses
function
gallbladder
genes
giant
glove
graceful
grow
grows
hairs
hands
harmless
head
heart
holds
hours
human
identical
image
imperfections
important
incomplete
inherently
internal
intricate
intrinsically
inversus
involved
lacy
leaf
left
level
lie
line
lined
liver
lobes
lungs
major
making
means
migrate
mirror
mirrored
molecular
molecule
nature
node
nucleic
organisms
organized
organs
pancreas
patterns
perfectly
pigs
pincer
pit
positions
pretty
property
proteins
proves
pushes
put
rapidly
reflected
reversals
ridges
rim
rotate
rotation
sense
shaped
shapes
shows
side
sides
similar
situs
small
snail
species
specific
spleen
starts
stomach
story
straight
striking
structures
sugars
symmetrical
symmetry
synchronized
tend
theory
tilt
tiny
translated
trellises
tube
turning
turns
twirl
ultimate
vital
weeks
whirl
whirls
wing
zoom