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BIOL 202 > Lecture 29 > Flashcards

Lecture 29 Flashcards

1
Q

general development of drosophila

A

within 1 day becomes multicellular, then at 9 days become full drosophila

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2
Q

describe 2 stages of cell division of drosophila

A
  1. NUCLEAR DIVISION
  2. CELLULARIZATION
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3
Q

what happens during drosophila nuclear division?

A

replicate DNA and divide many many times, then nuclei migrate to PM

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4
Q

what happens during drosophila cellularization?

A

individual nuclei are enclosed in PM to form cells

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5
Q

describe the genes used in drosophila development

A

at beginning: only using mRNA from mother (cytoplasmic inheritance) so there is no transcription

later: transcription of embryo’s own mRNA (mendelian inheritance)

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6
Q

2h to 10h to adult stages of drosophila

A

2h: embryo has defined anterior, posterior, back, and front regions

10h: body divided into 14 segments

adult: each segment forms specific structures

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7
Q

what was the heidelberg screen?

A

forward genetic screen to identify genes required for Drosophila embryo organization

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8
Q

2 types of genes investigated in heidelberg screen?

A
  1. maternal genes
  2. zygotic genes
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9
Q

what is the purpose of the screen for maternal genes?

A

find the mutations in the mother that prevent her offspring from completing embryonic development –> i.e. what mRNAs from cytoplasmic inheritance are required for development?

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10
Q

what are maternal-effect genes?

A

genes whose phenotype are determined by maternal genotype

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11
Q

experiment to find maternal-effect genes

A

paternal genotype doesn’t matter: if it carries mutation, offspring are normal

only maternal genotype matters: if it carries mutation, offspring are mutant

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12
Q

what is the purpose of the screen for zygotic genes?

A

find the genes from embryo that are required for embryonic development

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13
Q

what is drosophila development regulated by?

A

cascade of TFs that turn on genes

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14
Q

5 genes involved in drosophila development

A
  1. egg-polarity genes (maternal-effect genes)
  2. gap genes
  3. pair-rule genes
  4. segment-polarity genes
  5. homeotic genes
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15
Q

what is the role of the maternal-effect genes?

A

establish anterior-posterior axis

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16
Q

2 maternal-effect genes

A
  1. Bicoid
  2. Nanos
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17
Q

what is the role of bicoid?

A

form anterior axis

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18
Q

bicoid mutants

A

lack anterior structures (head, thoracic segments)

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19
Q

how does bicoid work?

A

concentration gradient: high [bicoid] at anterior end, low [bicoid] at posterior end

tells nucleus how far cell is from the front of organism

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20
Q

how is the bicoid concentration gradient formed? (3 steps)

A
  1. bicoid mRNA from mother localizes at anterior of embryo
  2. bicoid protein translated at anterior
  3. bicoid protein diffuses toward posterior
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21
Q

bicoid is _______ and ________ to form anterior structures

A

bicoid is REQUIRED and SUFFICIENT to form anterior structures

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22
Q

how do we know that bicoid is sufficient to form anterior structures?

A

inject bicoid mRNA –> anterior structures form

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23
Q

what is the role of nanos?

A

form posterior structures

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24
Q

what happens to nanos mutants?

A

lack posterior abdominal structures

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25
how is the nanos concentration gradient formed?
1. nanos mRNA from mother localizes at posterior of embryo 2. nanos protein translated at posterior 3. nanos protein diffuses towards anterior
26
role of nanos
inhibits translation of maternal HUNCHBACK mRNA
27
where is hunchback mRNA localized?
uniformly-spread thru embryo
28
describe the inhibition of hunchback by nanos
nanos is found in high [ ] at posterior and low [ ] at anterior --> since hunchback is uniformly-distributed, it gets inhibited by nanos so there is low [hunchback] at posterior and high [ ] at anterior
29
what is the role of gap genes?
translate maternal anterior-posterior gradients into subdomains
30
what is an example of a gap gene?
hunchback
31
how many gap genes are there? what type of proteins do they encode?
9 all encode TFs
32
what regulates gap genes? how?
regulated by maternal-effect genes, TRANSCRIPTIONALLY
33
what happens to gap gene mutants?
large gaps in the body due to loss of several consecutive segments
34
how does bicoid affect hunchback transcription?
hunchback promoter has 3 bicoid binding sites to activate hunchback expression at anterior (where there's high [bicoid])
35
role of pair-rule genes?
make 7 pairs of segments --> make 14 segments
36
what happens to pair-rule gene mutants?
absence of every other segment
37
how many pair-rule genes are there? what type of proteins are they?
8 all TFs
38
how are pair-rule genes expressed?
each gene is expressed in 7 stripes (stripes at diff positions depending on gene)
39
2 examples of pair-rule genes?
Eve and Ftz
40
what happens if you mutate Eve
7 stripes will be lost, but not the other stripes in each pair bc those are determined by Ftz
41
what does Eve mean?
Even-skipped
42
what regulates pair-rule gene expression?
maternal effect and gap genes
43
in Eve stripe 2, what is the relative expression of hunchback, bicoid, and two gap genes (giant and kruppel)?
high expression of Eve since at anterior, high [hunchback] and medium [bicoid] low [giant and kruppel]
44
describe the activation of eve in specific stripes
eve gene has different enhancers to regulate eve expression in diff stripes (ex. stripe 2 has its own enhancer, stripe 3,7 share an enhancer, stripe 4,6 share an enhancer, etc.) each enhancer has diff arrangements of binding sites for maternal-effect and gap genes to regulate expression
45
which genes are eve activators? how many binding sites do they each have?
bicoid - 5 binding sites hunchback - 1 binding site
46
which genes are eve repressors? how many binding sites do they each have?
kruppel - 3 binding sites giant - 3 binding sites
47
when are segment-polarity genes expressed?
once cellularization has occurred
48
what is the purpose of segment-polarity genes? (2)
to encode components of cell-cell signaling pathways (Hedgehog and Wingless) and define anterior/posterior within each segment
49
3 examples of proteins encoded by segment-polarity genes?
1. secreted proteins 2. membrane receptors 3. TFs
50
what genes control segment polarity genes?
pair-rule genes
51
what happens to segment polarity gene mutants?
half of each segment is mirrored (lose defined anterior vs posterior)
52
what is the purpose of homeotic genes?
determine the function of each stripe
53
what happens to homeotic gene mutants?
drosophila lack a certain structure which is replaced by another structure normally found on other body segments --> HOMEOTIC TRANSFORMATION
54
2 examples of homeotic mutants
1. Ultrabithorax - second thorax and set of wings 2. Antennapedia - leg instead of antenna
55
what are the homeotic genes called?
hox genes
56
how many hox genes are there?
8
57
what do hox genes encode?
homeo-domain family TFs
58
where are hox genes expressed?
expressed in specific segments and there is some overlap btwn segments
59
what control hox gene expression?
gap gene and pair-rule gene products
60

BIOL 202 (29 decks)

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