Developmental Biology Exam #2

Front 1

What is centrolecithal?

Back 1

describes the placement of the yolk in the centre of the cytoplasm of ovums. Many arthropod eggs are centrolecithal.

Front 2

What kind of cleavage do drosophila eggs undergo?

Back 2

Meroblastic

Front 3

What is meroblastic cleavage?

Back 3

characterized by or being incomplete cleavage as a result of the presence of an impeding mass of yolk material (as in the eggs of birds)

Front 4

What is a "syncytial" blastoderm?

Back 4

During these stages of nuclear division, the embryo is called a syncytial blastoderm, meaning that all the cleavage nuclei are contained within a common cytoplasm. No cell membranes exist other than that of the egg itself. MULTINUCLEATED! Drosophila eggs cellularize just before the 14th cleavage division

Front 5

When are pole cells observed? What do they establish?

Back 5

Pole cells are first observed just before the 12th division, they establish the posterior region of the embryo

Front 6

What does the longitudinal midline furrow define?

Back 6

The future venter

Front 7

When does the longitudinal midline furrow form?

Back 7

During gastrulation

Front 8

What does the transverse cephalic furrow partition the embryo into?

Back 8

A procephalon and a germ band

Front 9

What is a procephalon?

Back 9

the part of an insect's head that is in front of the segment in which the mandibles are located

Front 10

When is cellularization of the blastoderm complete?

Back 10

When the yolky cytoplasm has been completely covered by a simple (one-cell thick) epithelium consisting of columnar cells

Front 11

When is the embryonic genome transcriptionally active?

Back 11

Turns on in waves during the 6th and 14th cleavage divisions

Front 12

Why is the embryonic genome inactive before the 6th cleavage division?

Back 12

The egg is provisioned with specific kinds of maternal gene products--either proteins or mRNA--that play a major role in establishing the body axes of the embryo.

Front 13

What does the name of the mutation describe?

Back 13

The phenotype of the mutant

Front 14

What happens to the pole cells after the axes are defined?

Back 14

They are internalized, sinking from their original position at the posterior end and assuming an interior location among undifferentiated cells while retaining their identity.

Front 15

What is the amnioserosa?

Back 15

The amnioserosa is a epithelium of approximately 200 cells of the dorsal midline of the blastoderm the embryo . This epithelium is required for the own extension of the germinal band and dorsal closure.

Front 16

What is the fate of cells internalized at the future posterior?

Back 16

?

Front 17

What is the fate of cells internalized at the ventral furrow?

Back 17

?

Front 18

What are the paired caudal structures in larva?

Back 18

respiratory tubes (openings called spiracles

Front 19

What do the segment-specific groups of spines do?

Back 19

Help the maggot move through its surroundings (food) since it has neither legs nor wings

Front 20

Since the organs in the maggot are different from those in the adult, when was the body plan laid out?

Back 20

In the oocyte, long before the embryo was even formed, thats why we can see what the segments in the embryo/larva will eventually become.

Front 21

Are the segmented appendages of the adult (legs, antennae, mouthparts, wings, and genitalia) present in the larva?

Back 21

Yes, but they are in the form of primordial or precursor (undifferentiated) tissues called anlagen. (Anlage is german for investment). During the pupal stage, various anlagen "unfold" to become parts of the fly

Front 22

What are vitellaria?

Back 22

long tubes in each ovary that are partitioned into ovarioles.

Front 23

Where in the drosophila ovary are the germ cells and the youngest developing oocytes?

Back 23

In the anterior end of a vitellarium. Therefore, the most mature oocyte in each vitellarium in the posterior end of the vitellarium is closest to their common exit, the lateral oviduct.

Front 24

What is the spermatheca?

Back 24

It is a sperm case located into the common oviduct. In insects, most females mate just once, but manage to keep sperm alive in their spermathecae for the rest of their lives

Front 25

What are nurse cells?

Back 25

They provision the future egg with maternal gene products (mRNA and proteins) and accompany each oocyte

Front 26

What is the chorion?

Back 26

A proteinaceous shell that is formed by nurse cells. Makes fertilization complicated!

Front 27

How do the sperm fertilize if the chorion is in the way?

Back 27

Each chorion has a hole on its posterior end, through which sperm can enter and unite with the egg within. It's called the micropyle.

Front 28

Where does fertilization occur in drosophila?

Back 28

In the oviduct

Front 29

When does the oocyte get torpedo and gurken?

Back 29

The nurse cells provision it with them at the pre-vitellogenesis ovariole.

Front 30

What is torpedo?

Back 30

A membrane receptor protein (receoptor of gurken)

Front 31

What is gurken?

Back 31

A ligand which lies in the oocyte cytoplasm and attaches to its receptor (Torpedo).

Front 32

What do microtubules do?

Back 32

Microtubules are filamentous intracellular structures that are responsible for various kinds of movements in all eukaryotic cells.Microtubules are involved in nucleic and cell division, organization of intracellular structure, and intracellular transport, as well as ciliary and flagellar motility.

Front 33

What happens where torpedo-gurken binding occurs?

Back 33

microtubules start to grow (tubulin polymerizing anteriorly), dragging along bicoid mRNA.

Front 34

What is kinesin?

Back 34

A protein associated with microtubule function

Front 35

What does oskar mRNA associate with?

Back 35

Kinesin/microtubules

Front 36

What is gurken's relationship to the nucleus of the oocyte?

Back 36

It migrates with the nucleus to the dorso-anterior end and tells those follicle cells to become dorsal follicle cells

Front 37

Where do nanos and biocoid mRNA localize?

Back 37

nanos to the posterior end of the oocyte, bicoid to the anterior end

Front 38

How can we see the gurken expression domain with in situ hybridization?

Back 38

Gurken localizes to a fixed location in the dorso-anterior aspect of the unfertilized egg. ISH uses an antisense mRNA probe that hones in on the mRNA of interest and binds. We can see the probe/location of mRNA in situ.

Front 39

What does drosophila mean?

Back 39

"dew-loving"

Front 40

What happened to an embryo deficient in the torpedo gene?

Back 40

The entire fly was ventralized, resembled a torpedo.

Front 41

How is the dorsal aspect of the egg designated?

Back 41

gurken binds to torpedo, inhibits pipe

Front 42

How does the designation of the dorsal aspect ensure that the ventral aspect is delineated as well?

Back 42

gurken does not diffuse to ventral follicle cells, so they synthesize Pipe.

Front 43

What does pipe do?

Back 43

It starts a signal cascade which ends in dorsal proteins entering the nucleus and thus ventralizing the cell.

Front 44

How are genes known to be different if they produce the same phenotype (because they are involved in the same cascade)? For example, if torpedo is missing, it has the same effect as if gurken is missing. How do we know these arent a mutation of the same gene?

Back 44

Complementation test. If two animals with these mutations are crossed and they produce an UNC, it is on the same gene. If they are crossed and the progeny is WT, it is on different genes. The WT compensates/complements the mutant since the mutation is recessive.

Front 45

What does the dorsal protein do?

Back 45

It ventralizes the fly embryo

Front 46

What would a dorsal mutant embryo look like?

Back 46

It would only be dorsalized and have no ventralization

Front 47

What does the dorsal protein activate?

Back 47

The "ventral-aspect differentiation program" in the developing embryo. Dorsal protein also specifies the mesoderm (muscles, fat, and gonads), which proceeds to invaginate into the yolky cytoplasm.

Front 48

Which domain of the embryo expresses the highest levels of dorsal?

Back 48

The ventral domain, which is where the mesoderm-specifying genes are activated.

Front 49

What does the twist protein do?

Back 49

activates mesodermal genes

Front 50

What does the snail protein do?

Back 50

represses particular non-mesodermal genes that might already be active.

Front 51

What is bicoid?

Back 51

It is a transcriptional activator that activates anterior-specific gap genes, and represses posterior-specific gap genes.

Front 52

What does nanos do?

Back 52

It stops all the segments from being made so the mutant is super tiny (nano-sized).

Front 53

What is nanos localized to?

Back 53

Oskar

Front 54

j

Back 54

k