Download Sea squirt

Roundworm
Planarian
Sea squirt
Frog
The roundworm C. elegans has only 959
structural cells in its 1 mm long body. Scientists have mapped the route each of those
cells takes in the development of the worm
embryo into an adult. Most of these worms
are hermaphrodites, meaning they can reproduce by themselves.
The planarian flatworm is remarkable for its
ability to regenerate new individual worms
from any part of its body when it is cut into
pieces. Planarians can do this because their
bodies contain many stem cells, which can
generate any other type of cell the body
needs.
Adult sea squirts spend their lives attached to
the ocean floor and resemble hollow tubes.
But as young larvae, they can swim and look
a bit like tadpoles. Despite their simple appearance, these animals are believed to be
evolutionary cousins of vertebrates (animals with backbones).
Development is a process of transformation,
from a single cell (a fertilized egg) into an
adult. The tadpole is an interesting example
of this kind of metamorphosis. Scientists also
use eggs and embryos from some species of
frogs to study even earlier stages of development.
Zebrafish
Chick
ebony
Curly
When researchers want to study how genes
affect development in a vertebrate, they often
look at the zebrafish, which develops very
quickly and breeds in large numbers. By
studying what happens when a gene doesn’t
work right, scientists can also learn something about its normal function.
The eggs we use in cooking are unfertilized
and contain only yolk and albumin (egg
white). But fertilized eggs develop embryos
that will eventually grow into chicks. Biologists have looked inside the chicken egg to
study development for thousands of
years.
Drosophila fruit flies are usually tan-colored,
but flies with a defective ebony gene are nearly black. This is because the gene affected by
the ebony mutation inhibits the formation of
dark-colored pigments in the surface of the
body. Fly gene names usually describe
what happens when the gene doesn’t
work properly.
These flies’ wings don’t grow straight due to a
mutation in a single copy of a gene on the fly’s
second chromosome. Two copies exist of
nearly every gene in the genome, as a kind of
backup system. If the mutation of a single
copy causes a change in the body (called a
phenotype), it’s called a dominant mutation.
Antennapedia
eyeless
Ultrabithorax
Hox
The Antennapedia gene tells certain cells to
build a leg. In some Antp mutants, parts of the
head that would normally form antennae mistakenly grow into legs. Genes that are switched on in specific parts of the body, instructing the cells there of their roles, are called
selector genes.
Some genes have very precise job descriptions. The function of the eyeless gene is critical to the development of the fly’s compound
eye. Genes with similar sequences in different
species are called homologs. eyeless homologs serve as master controllers of eye development in many other animals, including humans, as well.
Ultrabithorax is one of a group of genes that
sets up the basic pattern of the Drosophila
body. Flies are segmented, and genes tell the
embryo what each segment’s identity should
be. In this Ubx mutant, the body accidentally
builds a second pair of wings in the middle
of the fly.
The Hox family of genes functions in some of
the earliest steps of development, such as
letting the embryo know where certain parts of
the body should appear, and in what order.
These genes appear in the same sequence
on chromosomes as they are expressed in
the body, but no one yet knows the reason why. Antennapedia and Ubx are
both Hox genes.
Zygote
Morula
Blastocyst
Gastrula
The fertilized egg cell, called a zygote, is the
first step on the path of embryonic development. Genetic information from both the mother
and father is needed to ensure that the embryo
grows normally. Every one of us passed
through the one-cell zygote stage.
When its cells have divided three times, the tiny
eight-cell embryo is called a morula because
under a microscope it looks like a berry (morula
is Latin for mulberry). Before this stage, the
cells of the embryo are only loosely connected,
but in the morula they clump together and
stick to each other much more tightly.
As the embryo grows, a hollow space grows in
its center and fills with fluid. At this stage, the
embryo, called a blastocyst, is still not attached
to the wall of the mother’s womb and cannot
survive independently. But it now contains the
embryonic stem cells that will ultimately
form all of the cells in the body.
After attaching to the wall of the uterus, the
cup-shaped gastrula embryo is set to begin
turning itself into a body. It begins by organizing into three “germ layers” that are the sources
of all of the body’s tissues and organs. These
three layers – ectoderm, mesoderm and endoderm – are seen in the plans for animal bodies ranging from worms to humans.
Neurula
Neonate
Corpuscle
Melanocyte
In the neurula, one of the germ layers - the ectoderm - reorganizes into a surface layer that
will become the skin and a second region that
folds inward, forming a tube that will give rise to
the central nervous system. The neurula gradually starts to resemble an animal body, as
structures called somites that will form
the animal's backbone begin to appear.
Birth is not the end of development - the newborn mouse is still hairless, blind and helpless but the embryo has come a long way since its
start as a single cell. For some animals, including humans, experiences in the world outside
the mother’s womb play a big part in shaping the individual.
Cells floating free in the body, such as red blood
cells, are called corpuscles. These red blood cells
have no nucleus, and are no longer able to renew
themselves by dividing in two. To maintain its
supply of fresh red blood cells, the human body
makes use of stem cells whose job is to produce new red corpuscles, which they make
at a rate of about 200,000,000,000 every
day.
Cells called melanocytes give skin, hair and eyes
their color. Human melanocytes contain two
types of coloring pigments; one for brown and
black, one for yellow, orange and red. During embryonic development, genes help determine a
person’s appearance. Later, factors such as
aging and the environment also play important roles.
Syncytium
Neuron
Gamete
ES cell
Most cells contain only a single nucleus, which
contains the chromosomes that store its DNA.
Some cells however, join together and hold many
nuclei within a single membrane. Muscle is one
type of syncytium. This shared structure allows
for rapid communication of signals for the entire muscle to contract or relax at the same
time. The placenta that provides the embryo’s nutrition is another syncytial cell.
Neurons are the primary cells of the brain and
nervous system. Neurons connect to and communicate with each other by sending and receiving signals at contact points called synapses,
which grow and change in the embryo and
throughout adult life. The adult human brain is
made up of about 100 billion neurons and
perhaps 100 trillion synaptic connections.
Nearly every cell in the body contains exactly the
same genetic information in its DNA, but only
very few cells, known as gametes, can pass that
information from one generation to the next.
Gametes have only half as many chromosomes
as other cells, but when a male and a female
gamete fuse, their genetic information
combines to initiate the development of a
new individual.
The very early embryo looks like a hollow ball of
cells, but one area, called the inner cell mass,
contains stem cells that can generate the many
other types of cells in the body. There are about
250 different types of cells in the human body,
and embryonic stem cells are able to give rise
to all of them. Other kinds of stem cells are
more limited and naturally produce only
certain types of cells.
Student
Tech
Vet
Postdoc
The researcher’s career begins as a graduate student, learning the concepts and
techniques needed to study the natural
world. Students of developmental biology
have to master a wide range of fields, from
genetics and cell biology to the processes of evolution. The youngest generation of scientists, grad students represent the future of the field.
Technicians perform a wide range of the
lab’s day to day work. They are responsible
for making sure that experimental protocols
are followed correctly, putting their education to use in handling advanced technology
and performing complex techniques.
Specialists in animal health and welfare hold
a degree in veterinary medicine, and ensure
that animals being studied by scientists are
comfortable, healthy and cared for properly.
Animal welfare is an essential part of biological research and is a responsibility all
good scientists take very seriously.
The postdoctoral researcher is a full-fledged
scientist, usually working on a single project
and intent on developing a better understanding of a specific biological process or
phenomenon. Their focus makes postdocs
specialists in their fields, and their enthusiasm sustains them through long
hours at the bench.
How to play
(2 players)
Shuffle and deal the cards face down so
that each player has a Deck with an
equal number of cards. Each player
draws a Hand of 5 cards from the top of
the deck.
P. I.
Director
Heading a laboratory, the principal investigator needs to wear many hats – as a research scientist as well as manager, mentor
and representative of the entire lab’s work.
Researchers can only become PIs after
proving their ability by publishing the results of their own original studies.
The director of a research institute often remains an active laboratory scientist, but one
who has also taken on the responsibility of
overseeing the success of the institute’s research mission. Although always pressed
for time, the best research directors keep
the door to their offices open at all
times.
For each round, the two players choose
one of their cards and lay them on the
table at the same time. Each card has a
point value (1~10) shown in the upper left
corner of the card. Next, check the
monkeys in the bottom right corner of the
two cards, using the chart below to check
for special monkey vs. monkey effects.
Mizaru cards score
double against Iwazaru
Iwazaru cards score
double against Kikazaru
Kikazaru cards score
double against Mizaru
The card with the higher point total wins
and the winning player takes both cards,
placing them to the side in a Stack. In the
event of a draw, the players leave the
cards on the table and play a new round,
and the winning player takes all cards in
play.
At the end of the round, the players draw
one new card each from the top of their
Decks, add them to their Hands and
continue play. When a player’s Deck is
exhausted, the player shuffles the Stack
and uses that as a new Deck (starting a
new Stack the next time the player wins a
round). Play continues until one player
has won all of the cards.