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zBIO 3147 - Animal Development > Specification: Drosophila (lec 12/13) > Flashcards

Specification: Drosophila (lec 12/13) Flashcards

1
Q

(T/F) Morgan demonstrated that genes are carried in chromosomes and are the mechanical basis of heredity.

A

True!

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2
Q

Why is Drosophila melanogaster a model organism?

A

1) Development process is really fast (can develop an adult fly in ~10 days + sexual maturation is fast)

2) Easy to take care of (cheap)

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3
Q

What happens after fertilization in the life cycle of Drosophila melanogaster?

A

Following fertilization, EMBRYOGENESIS begins with the division of nuclei (cleavage) and their subsequent cellularization, which is then followed by the cell and tissue movements of GASTRULATION and organ formation.

The embryo hatches out as a FIRST INSTAR LARVA that grows, going through two MOLTS to become a THIRD INSTAR LARVA, which becomes a pupa that METAMORPHOSES into the adult fly.

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4
Q

What kind of nuclear divisions and cleavage do flies have?

A

SYNCYTIAL nuclear divisions; SUPERFICIAL cleavage (centrolecithal –> meroblastic)

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5
Q

The early nuclear divisions occur centrally within a ___________.

Later, the nuclei and their cytoplasm islands migrate to the _________ of the cell, creating a __________ blastoderm.

After cycle 13, the _______ blastoderm forms by _________ of cell membranes between nuclei.

The ______ cells (germ cell precursors) form in the __________.

A

Syncytium

Periphery; Syncytial

Cellular; Ingression

Pole; posterior

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6
Q

(T/F) Chromosomes divide at the cortex of a syncytial blastoderm. Because there are cell boundaries, actin forms regions within which each nucleus divides.

A

False!

There are NO CELL boundaries but actin can be seen forming regions within which each nucleus divides. Microtubules are present as well.

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7
Q

What is coordinated through the cytoskeleton during the formation of the cellular blastoderm in Drosophila?

A

Nuclear shape change (ELONGATION) and CELLULARIZATION are coordinated through the cytoskeleton.

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8
Q

How does the ventral furrow form?

A

Ventral furrow begins to form as cells flanking the ventral midline invaginate (moving inward of the embryo).

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9
Q

What does the ventral furrow do after being formed?

A

The ventral furrow becomes a tube that invaginates into the embryo and then flattens and generates the MESODERMAL organs.

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10
Q

What is the Twist protein?

A

Mesoderm marker

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11
Q

During _________, the ventral furrow forms in Drosophila.

A

GASTRULATION

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12
Q

Closing of ventral furrow, with ________ cells placed internally and surface ________ flanking the _________ ________.

A

mesodermal; ectoderm; ventral midline

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13
Q

(T/F) Head region is found anterior to the cephalic furrow, while non-head is found posterior to the cephalic furrow.

A

True!

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14
Q

Pole cells and posterior endoderm ______ into the embryo through posterior midgut invagination on the ______ side of the embryo.

A

Sink; Dorsal

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15
Q

What is the cephalic furrow?

A

Cephalic furrow separates the future head region (procephalon) from the germ band, which will form the thorax and abdomen.

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16
Q

What is a germ band?

A

Germ band is a collection of cells of the Drosophila embryo that forms during GASTRULATION by convergence and extension that includes all the cells that will form the TRUNK of the embryo and the THORAX and ABDOMEN of the adult.

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17
Q

Match the following terms to their definitions regarding the segmentation of Drosophila:

1) Ma, Mx, and Lb
2) T1-T3
3) A1-A8

A) abdominal segments
B) correspond to the mandibular, maxillary, and labial head segments
C) thoracic segments

A

Ma, Mx, and Lb: correspond to the mandibular, maxillary, and labial head segments

T1-T3: thoracic segments

A1-A8: abdominal segments

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18
Q

Each segment (Ma, Mx, Lb, T1-3, etc) has an ___________ and ___________ compartment.

A

Anterior; posterior

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19
Q

What is a parasegment?

A

Parasegment consists of the posterior compartment of one segment and the anterior compartment of the segment in the next posterior position.

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20
Q

During gastrulation, there is an ________ of the germ line and the beginnings of segmentation where there are subtle __________ to mark incipient segments.

Then, there is a _______ of the germ line, where segments become visible as the cells constrict on each other.

A

Extension; Indentations

Retraction

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21
Q

(T/F) Not only are the segments visible during germ band retraction, but other territories of the dorsal head, such as the clypeolabrum, procephalic region, optic ridge and dorsal ridge are also visible.

A

True!

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22
Q

What drives the invagination of ventral furrow?

A

Physical forces drive invagination of the ventral furrow.

EPITHELIAL ADHESIONS paired with differential activation of MYOSIN (forms contractile filaments) and TISSUE GEOMETRY create mechanical constraints that affect the orientation of actomyosin meshworks.

The combination of tissue geometry and tension of these anterior-to-posterior meshworks cause the tissue to FOLD INWARD at a right angle to the anterior-posterior axis.

23
Q

(T/F) Internal and external organs can emerge from the head, thoracic, and abdominal segments.

A

True!

For example, T1 contributes to making legs, wile T2 makes wings and legs!

24
Q

In a wild-type embryo, the dorsal protein is only in the ________ nuclei.

A dorsalized mutant has no __________ of Dorsal protein in any nucleus.

In a ventralized mutant, Dorsal protein has ______ the nucleus of every cell.

A

Ventralmost

Localization

Entered

25
Q

The most ventral part becomes the __________.

The next higher portion becomes the __________ _________.

The lateral and dorsal ectoderm can be distinguished in the _______.

The dorsalmost region becomes the ___________, which is the extraembryonic layer that surrounds the embryo.

A

Mesoderm

Neurogenic ectoderm

Cuticel

Amnioserosa

26
Q

(T/F) The translocation of Dorsal protein into ventral, but not lateral or dorsal, nuclei produces a gradient whereby the ventral cells with the most Dorsal protein becomes the ectoderm precursors.

A

False!

The translocation of Dorsal protein into ventral, but not lateral or dorsal, nuclei produces a gradient whereby the ventral cells with the most Dorsal protein becomes the MESODERM precursors.

27
Q

Match the genes expressed in the regions:

1) Neurogenic ectoderm (ventral)

2) Lateral ectoderm

3) Mesoderm above the intermediate neuroblasts

4) Dorsalmost tissues

A) MUSCLE-SPECIFIC HOMEOBOX GENE

B) DECAPENTAPLEGIC

C) NERVOUS SYSTEM DEFECTIVE

D) NEUROBLAST DEFECTIVE GENE

A

Neurogenic ectoderm (ventral): NERVOUS SYSTEM DEFECTIVE

Lateral ectoderm: NEUROBLAST DEFECTIVE GENE

Mesoderm above the intermediate neuroblasts: MUSCLE-SPECIFIC HOMEOBOX GENE

Dorsalmost tissues: DECAPENTAPLEGIC

28
Q

The action of (maternal effect, gap, pair rule, segment polarity) genes define the _______ domains of the _______ genes that define the _________ of each of the segments.

A

Spatial; Homeotic; Identities

29
Q

Match the following genes to their definitions:

1) Maternal axis determination genes

2) GAP genes

3) Pair-rule genes

4) Segment polarity genes

A) Enable the expression of the pair-rule genes

B) Divides the embryo into segment-sized units along the anterior-posterior axis.

C) Form gradients and regions of morphogenetic proteins, which are TFs that activate the GAP genes.

D) Divides the embryo into regions about two segments wide. Influences segment polarity genes

A

Maternal axis determination genes: Form gradients and regions of morphogenetic proteins, which are TFs that activate the GAP genes.

Gap genes: Enable the expression of the pair-rule genes

Pair-rule genes: Divides the embryo into regions about two segments wide. Influences segment polarity genes

Segment polarity genes: Divides the embryo into segment-sized units along the anterior-posterior axis.

30
Q

Match the following genes to their examples:

1) Maternal axis determination genes

2) GAP genes

3) Pair-rule genes

4) Segment polarity genes

A) Fushi tarazu

B) Bicoid

C) Engrailed

D) Hunchback and Kruppel

A

Maternal axis determination genes: Bicoid

GAP genes: Hunchback and Kruppel

Pair-rule genes: Fushi tarazu (forms 7 bands across the embryo)

Segment polarity genes: Engrailed

31
Q

(T/F) Maternal axis determination genes are dumped into the egg from the female in the form of proteins/morphogens pre-cellularization. Through the ratio of these morphogens, what genes will be expressed is dictated post-cellularization.

A

True!

32
Q

What are bicoid and nanos? Where are they located? What do they do?

A

Bicoid is a maternally deposited mRNA located in the ANTERIOR part of Drosophila.

Nanos is located in the POSTERIOR part.

They form a coordinate system based on their ratios. Each position along the axis is distinguished from any other position! When the nuclei divide, each nucleus is given its positional information by the ratio of these proteins.

These gradients activate the TRANSCRIPTION of the genes specifying the SEGMENTAL IDENTITIES of the larva and adult fly.

33
Q

What does the slogan “Find it, Move it, Lose it” mean? Use BICOID gene as an example.

A

“Find it, Move it, Lose it” helps study the function of genes.

Find it: Where is the Gene located? Bicoid is located in the anterior part.

Move it: What happens when Bicoid is added to the middle of an embryo or at the posterior (regions where it isn’t found)? Formation of anterior structures there.

Lose it: What happens when Bicoid isn’t present in the fly? Formation of posterior structures in both poles.

34
Q

Where is caudal found in a Drosophila embryo?

A

In the posterior end!

It helps specify posterior fates.

35
Q

The ______, _____, _____ and _____ mRNAs are deposited in the oocyte by the ovarian nurse cells.

The bicoid message is sequestered _______; the nanos message is localized to the _________ pole.

A

Bicoid; nanos; hunchback; caudal

Anteriorly; Posterior

36
Q

(T/F) Upon translation, the bicoid protein gradient extends from the posterior to anterior, while the Nanos protein gradient extends from the anterior to posterior.

A

False!

Upon translation, the bicoid protein gradient extends from the ANTERIOR to POSTERIOR, while the Nanos protein gradient extends from the POSTERIOR to ANTERIOR.

37
Q

Nanos inhibits the translation of __________, while Bicoid inhibits the translation of ___________. This inhibition results in opposing gradients (CROSS REGULATION).

A

Hunchback; Caudal

*nanos found in posterior; hunchback must be found in anterior
*bicoid found in anterior; caudal must be found in posterior

38
Q

(T/F) Bicoid is concentrated in the nuclei.

A

True!

39
Q

What happens to the Drosophila embryo when there is a bicoid-deficient mutant?

Do all development gene mutations result in such adverse effects?

A

Bicoid-deficient mutant: head and thorax replaced by a second set of posterior structures! in between there is some anterior structure.

No! Not all development gene mutations result in such adverse effects!

40
Q

Why are GAP genes called GAP genes?

A

Gap genes (ex. Kruppel) have a large area of gene action in an embryo.

When there is a mutation in the gene, the large area of gene action disappears, creating a huge GAP!

41
Q

What happens to the larva when there are mutations in pair rule (ex. fushi tarazu) and segment polarity (engraile) genes?

A

Pair rule mutations: All 7 segments that express fushi tarazu are gone!

Segment polarity mutations: All 14 segments that express engrailed are also missing!

42
Q

(T/F) Wingless is a segment polarity gene, like engrailed. Wherever engrailed is expressed, wingless is expressed there as well.

A

False!

Wingless genes are found in opposing regions than engrailed.

43
Q

1) Which genes’ expressions are regulated by the anterior-posterior gradient of bicoid and caudal?

2) What does Tailless do?

A

1) The anterior-posterior gradient of bicoid and nanos regulates expression of KNIRPS, HUNCHBACK, KRUPPEL, and GIANT.

2) Tailless prevents these patterning pathways at the terminal ends of the embryo.

44
Q

Fill in the blanks regarding the gap gene network:

1) There is a mutual inhibition of ________ and _________, positioning _____ protein domain at around 60-80% along the anterior-posterior axis.

2) Hunchback inhibits _________ expression at high concentrations but ________ it at low concentrations.

3) _______ and _______ mutually inhibit each other’s syntheiss.

A

1) Knirps; hunchback; knirps

2) Kruppel; promotes

3) Kruppel; Giant

*these interactions are supported by mathematical modeling, genetic data, and biochemical analyses.

45
Q

(T/F) Even skipped and fushi tarazu are gap genes where each is expressed as a series of four stripes.

A

False!

Even skipped and fushi tarazu are PAIR RULE genes where each is expressed as a series of SEVEN stripes.

46
Q

(T/F) For even skipped gene, certain enhancers only influence certain stripes and not others! By using reporter b-galactosidase gene, we can tell which enhancer is responsible for which stripe.

A

True!

47
Q

What happens when there is a GIANT deficiency in fly embryos?

A

Giant regulates even-skipped gene by restricting the region it can be expressed.

When giant is missing, certain stripes are fatter than they should be!

48
Q

The enhancer element for stripe 2 regulation of the even-skipped gene contains binding sequences for several ________ and _____ gene proteins.

Every activator site is closely linked to a repressor site, suggesting for ________ _______ at these positions. A protein that is a repressor for one stripe can be an ________ for another stripe!

A

Maternal; Gap

Competitive interactions; Activator

49
Q

1) Which type of genes initiate the expression of the wingless and engrailed genes?

2) In which cells is the engrailed gene expressed?

3) In which cells is the wingless gene expressed?

A

1) Pair rule genes initiate the expression of the two segment polarity genes

2) The engrailed gene is expressed in cells that contain high concentrations of Even-skipped or fushi tarazu proteins

3) The wingless gene is expressed in cells where neither even-skipped or fushi tarazu are active but a different third gene.

50
Q

The continued expression of wingless and engrailed is maintained by interactions between the engrailed and wingless expressing cell. How?

A

Wingless protein (a morphogen) is secreted and diffuses to surrounding cells. In those cells competent to express Engrailed, wingless protein binds to receptor proteins, which enables the activation of the engrailed gene via the WNT SIGNAL TRANSDUCTION PATHWAYS.

Engrailed protein (not a morphogen) activates the transcription of the HEDGEHOG gene (morphogen). Hedgehog proteins diffuse and bind to receptors on neighbouring cells, enabling the transcription of the wingless gene and the subsequent secretion of the wingless protein.

51
Q

(T/F) Hox genes can be classified into two complexes: Antennapedia and Bithorax. The antennapedia complex is located on the anterior region of the fly, while the bithorax complex is located on the posterior region.

A

True!

52
Q

The __________ expression pattern separates the body into segments; __________ and _________ separate the thoracic and abdominal regions; _________ shows the placement of jaws and the beginning of limbs.

A

Engrailed; Antennapedia; Ultrabithorax; Distal-less

53
Q

1) Where do the wings of the wild-type fruit fly emerge from?

2) What happens when there are THREE mutations in the cis-regulators of the Ultrabithorax gene?

A

1) Wings of the wild-type fruit fly emerge from the second thoracic segment

2) A four winged fruit fly is constructed! These mutations transform the third thoracic segment into another second thoracic segment (halteres into wings)

54
Q

(T/F) An Antennapedia mutation converts antennae into legs.

A

True!

zBIO 3147 - Animal Development (11 decks)

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