drosophila development

Question 1

what is syncytial development

Answer 1

there is one large egg with lots of nuclei

Question 2

outline cellularisation

Answer 2

at division 14 the nuclei become individual cells due to the invagination of the original cell membrane

Question 3

outline the effects of gastrulation

Answer 3

it results in the formation of a germ band. this allows differentiation of the endoderm, ectoderm, and a presumptive mesoderm/ germ cells

Question 4

outline segmentation

Answer 4

it begins with the retraction of the germ band and allows the definition of the head, thorax and abdomen

Question 5

how are axes established in the oocyte

Answer 5

through interaction with the surrounding follicle cells

Question 6

what is the initial action of gurken mRNA within the oocyte

Answer 6

is is translated at the posterior, acting as a ligand for torpedo receptors on follicle cells and making them posterior follicles

Question 7

what is the role of nurse cells

Answer 7

they transfer mRNA to the oocyte. bicoid binds dynein and moves to anterior, oskar binds kinesin and nanos binds translated oskar protein and both move to posterior. gurkin and nucleus relocate to dorsal

Question 8

how does the dorsal ventral axis form

Answer 8

gurken is translated dorsally and binds torpedo receptors, giving follicle cells a doral morphology. in the absence of gurken a vental pipe is synthesised

Question 9

what is dorsal

Answer 9

a TF which acts as a morphogen. it is expressed in ventral cells and disparity in concentration causes different fates

Question 10

how does the anterior posterior axis form

Answer 10

the morphogenic gradient of anterior bicoid mRNA and posterior nanos mRNA

Question 11

what is bicoid

Answer 11

a TF and transcriptional regulator which inhibits caudal mRNA translation in the anterior (translated in absence at the posterior)

Question 12

what is nanos

Answer 12

a transcriptional regulator which inhibits translation of hunchback mRNA at the posterior

Question 13

what is patterning and name the three main types

Answer 13

patterning is mutation which alters the banding and segmentation of the organism. it can be gap gene, pair rule or segment polarity

Question 14

what is gap gene patterning

Answer 14

TFs which regulate each other and define broad regions of the embryo, therefore mutants have whole missing segments

Question 15

what is pair rule patterning

Answer 15

different bands express different genes sequentially and therefore mutations are seen in a pattern across the bands of the organism

Question 16

what is segment polarity gene patterning

Answer 16

they affect the polarity and organisation of cells and therefore mutants affect all the cells within the organism

Question 17

what does homeotic Hox gene expression cause

Answer 17

they encode TFs and specify structures specific to each segment, therefore mutants can have dramatically different morphology