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Animal Developmental Biology > Drosophila > Flashcards

Drosophila Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a holometabolous life cycle?

A

The insect undergoes complete metamorphosis. The larval forms look completely different than the adults

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2
Q

What is hemimetabolous life cycle?

A

The insect undergoes incomplete metamorphosis. The larval form looks like a mini adult

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3
Q

Do flies have a holometabolous or hemimetabolous life cycle?

A

Holometabolous

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4
Q

What effects do the nurse and follicle cells have on the embryo during oogenesis?

A

The nurse and follicle cells determine the egg and embryo axes by producing oskar and bicoid mRNA. The follicle cells also produce paracrine and juxtacrine signals

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5
Q

What type of yolk distribution do fly eggs have?

A

Centrolecithal

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6
Q

What type of cleavage do flies have?

A

Superficial. Karyokinesis occurs without cytokinesis, so the embryo is syncytial

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7
Q

What happens for the first 11 divisions?

A

Karyokinesis without cytokinesis

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8
Q

What happens after the 9th division?

A

The nuclei migrate to the outer cytoplasm of the embryo

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9
Q

What happens at the 12 division?

A

The nuclei are segregated into individual cells and form the cellular blastoderm

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10
Q

How does the cellular blastoderm form?

A

Microtubules grow from the outer cytoplasm towards the yolk, and actin filaments pinch off the new cells

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11
Q

What three proteins work to cause the midblastula transition?

A

Smaug, Zelda, and cyclin regulators

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12
Q

What does Smaug do? Where does it come from?

A

Accumulates over time and destroys maternal mRNA. Is a maternal signal

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13
Q

What does Zelda do? Where does it come from?

A

Regulates transcription by allowing the chromatin to unwind for transcription to occur. Is a maternal signal

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14
Q

What do cyclin regulators do?

A

Regulate how long each cell division takes

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15
Q

Where does gastrulation occur?

A

The ventral furrow

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16
Q

What is the ventral furrow?

A

An invagination of future mesoderm cells that eventually closes to form a tube

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17
Q

Where does the endoderm tissue come from during gastrulation?

A

Anterior and posterior pockets

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18
Q

Where is the neural ectoderm during gastrulation?

A

Surrounding the ventral furrow

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19
Q

How does the germ band expand over the posterior end of the embryo?

A

Convergent extension

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20
Q

How are the different segments of the larva created during gastrulation?

A

Convergent extension of the germ band over the posterior end of the embryo, which then contracts back to its original position and leaves the segments together in the correct places

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21
Q

What are the segments found on a fly larvae?

A

8 abdominal segments (A1-A8), 3 thoracic segments (T1-T3) and 3 head segments

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22
Q

How do the germ cells get inside the embryo?

A

Invagination of endoderm tissue

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23
Q

What are imaginal disks?

A

Discs of tissue in the larva that give rise to corresponding adult features

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24
Q

How does syncytial specification work?

A

Cytoplasmic signals with different locations in the cytoplasm as a gradient

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25
Q

What 3 maternal signals establish the anterior-posterior axis in the oocyte?

A

Bicoid, oskar, nanos

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26
Q

What 5 maternal signals establish the dorsal-ventral axis in the oocyte?

A

Gurken, torpedo, pipe, nudel, dorsal

27
Q

Where does Gurken come from?

A

Synthesized by the oocyte

28
Q

What does Gurken do?

A

Leaves the egg cell and binds to Torpedo on the neighbouring follicle cells to tell them to create a reciprocal signal back to the egg

29
Q

What do the follicle cells tell the oocyte to do when receiving signalling by Gurken?

A

Tells the oocyte to make Par1 to anchor microtubules

30
Q

How does anchoring the microtubules contribute to positioning of the anterior-posterior axis?

A

It allows the microtubules to grow in a particular orientation, with the minus end growing out as the oocyte expands anteriorly

31
Q

Does bicoid bind to kinesin or dynein? Which way does it go?

A

Dynein, goes to the anterior end

32
Q

Does oskar bind to kinesin or dynein? Which way does it go?

A

Kinesin, goes to the posterior end

33
Q

What does oskar do?

A

Gets translated into a protein at the posterior end of the cell where it holds on to nanos mRNA

34
Q

What is the function of bicoid and nanos?

A

Transcription factors

35
Q

Where is the nucleus of the oocyte going as the cell grows? What is it doing?

A

The nucleus is moving anteriorly, and still making Gurken as it moves

36
Q

What does Gurken do as the nucleus is moving anteriorly?

A

Diffuses into the dorsal follicle cells and shuts off transcription of Pipe

37
Q

Where is Pipe expressed? What does it do?

A

Expressed in the ventral follicle cells. It turns on Dorsal transcription

38
Q

What does Dorsal do?

A

Is a transcription factor activated by Pipe signalling, and it stays near the ventral side and creates a ventral phenotype. It activates Twist and Snail and surppresses Dpp

39
Q

What does Twist do?

A

Specifies mesoderm cells on the ventral side

40
Q

What does Snail do?

A

Suppresses non-mesoderm genes in the ventral side

41
Q

What does Dpp do?

A

Specifies dorsal ectoderm through BMP signalling

42
Q

Why is BMP being expressed on the dorsal side in insects?

A

The nervous system is ventral in insects, and where there’s BMP there is no neural ectoderm

43
Q

What is a gene hierarchy?

A

Step by step progression of which genes are activated from general to specific

44
Q

What is the gene hierarchy in fly embryos?

A

Maternal effects -> GAP genes -> pair rule genes -> segment polarity genes

45
Q

What does bicoid do?

A

Transcription factor that shuts off posterior related genes in the anterior end of the embryo. Activates hunchback and inhibits nanos and caudal

46
Q

What does nanos do?

A

Transcription factor that shuts off anterior related genes in the posterior end of the embryo. Activates caudal and inhibits bicoid and hunchback

47
Q

Where is torso expressed and what is it doing?

A

Expressed in the centre of the embryo and creates torso-like features

48
Q

What do GAP genes specify? What happens if one is mutated?

A

Large areas of the embryo. Mutation leads to the loss of large regions of the body

49
Q

What causes the expression pattern of the GAP genes?

A

The maternal effect

50
Q

Where is kruppel expressed? What is it doing?

A

Expressed in the centre of the embryo. It inhibits Giant

51
Q

Where is Giant expressed? What is it doing?

A

The anterior and posterior ends of the embryo. It inhibits Kruppel

52
Q

How do we get clean boundaries of gene expression for the GAP genes?

A

They inhibit each other, so only one or the other can be expressed in a region

53
Q

What do the pair-rule genes specify? What happens if one is mutated?

A

They divide into periodic segments and are expressed in every second fragment. Mutations result in the loss of every second fragment

54
Q

What are the two pair-rule genes?

A

Fushi tarazu and even-skipped

55
Q

What determines the expression pattern of the pair-rule genes?

A

Expression patterns of the GAP genes, especially where and how they overlap

56
Q

Which two stripes are inhibited by Giant?

A

2 and 5

57
Q

What do segment polarity genes do? What happens if one is mutated?

A

They give polarity to each segment. Each segment will have defects if one is mutated

58
Q

What determines the expression pattern of the segment polarity genes?

A

The expression pattern of the pair-rule genes

59
Q

What products do segment polarity genes produce, in general?

A

Parts of the Wnt and Hedgehog signalling pathways

60
Q

Do gene expression parasegments line up with the actual segments on the embryo?

A

Not completely, but there is overlap

61
Q

What establishes the boundaries of the parasegments?

A

A positive feedback loop between engrailed, wingless, and hedgehog

62
Q

Where is wingless expressed? What does it do?

A

Where both fushi tarazu and even-skipped are absent. It’s a paracrine signal that activates the Wnt pathway and turns on engrailed and hedgehog in nearby cells

63
Q

Where is engrailed expressed? What does it do?

A

Where either fushi tarazu or even-skipped is expressed. It’s a transcription factor that turns on hedgehog

64
Q

Where are both wingless and engrailed expressed?

A

Boundaries of the parasegments

Animal Developmental Biology (26 decks)

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