Developmental biology 1

Question 1

true or false, all embryos in early development have a similar body plan, and specialized features come later

Answer 1

true

Question 2

how come we know the entire complete development of C. elegans?

Answer 2

only 100 million base pairs, a small cheap and easy

Question 3

when does a C. elegans egg become asymmetrical?

Answer 3

sperm entry

Question 4

how does a C. elegans egg become asymmetrical after sperm entry?

Answer 4

Sperm entry causes contraction of actin filaments, leading to cytoplasmic flow of PAR proteins due to centrosome positioning, which creates asymmetry

Question 5

What is the first division of a C. elegans embryo?

Answer 5

egg divides into AB (anterior) and P1 (posterior).

Question 6

at which stage are the four axises of development established in C elegans?

Answer 6

at the 4 cell stage

Question 7

which four cells are present at the four cell stage?

Answer 7

ABp, P2, ABa, EMS

Question 8

Why do blastomeres become smaller during early cleavage?

Answer 8

Rapid mitosis without G1 or G2 phases reduces cell size.
- cleavage vs division

Question 9

Early cleavage divisions in C elegans don’t depend on ________ ____, but instead on _________ _______.

Answer 9

zygotic DNA, maternal factors

Question 10

where do maternal factors/mRNA from C elegans come from?

Answer 10

the egg

Question 11

What does cell staining in C. elegans help determine?

Answer 11

Lineage and fate of specific cells (e.g., from P1 cell).

Question 12

What are founder cells in C. elegans?

Answer 12

Cells whose descendants are committed to specific fates.

Question 13

what do pluripotent cells give rise to?

Answer 13

all cells of the embryo

Question 14

what do totipotent cells give rise to?

Answer 14

embryo or placenta

Question 15

founder cells are _____potent

Answer 15

multipotent

Question 16

How does early blastomere positioning affect development?

Answer 16

cell-cell interactions in the blastomere influence cell fate

Question 17

what polarises the C elegans egg?

Answer 17

localisation of PAR proteins after sperm and centrosome induced cortical flow

Question 18

describe PAR positioning after cortical flow

Answer 18

PAR1 and PAR2 in the POSTERIOR
PAR3 and PAR4 in the ANTERIOR

Question 19

what does PAR3 do?

Answer 19

inhibits spindle rotation

Question 20

how does PAR3 influence asymmetrical cell division

Answer 20

PAR3 in the anterior inhibits spindle rotation, the posterior rotates and we have asymmetric cell divsion

Question 21

What determines unequal daughter cells in C. elegans?

Answer 21

Spindle orientation and polarised PAR

Question 22

What signals do P2 cells give to ABp and EMS?

Answer 22

Notch to ABp and Wnt to EMS

Question 23

What does Notch signalling do in C. elegans?

Answer 23

Induces differentiation in ABp cell

Question 24

What does Wnt signalling cause in EMS?

Answer 24

induces a Pop1 gradient in EMS → mesoderm (high Pop1) and endoderm (low Pop1).

Question 25

What is a syncytium in Drosophila?

Answer 25

A single cytoplasm with many nuclei due to nuclear division (karyokinesis) without cytokinesis.

Question 26

when does the drosophila egg become polarised?

Answer 26

it is already polarised

Question 27

What proteins are localised in the Drosophila egg causing polarity?

Answer 27

Bicoid (anterior) and nanos (posterior)

Question 28

What happens after nuclei migrate to the periphery in Drosophila?

Answer 28

Cellularization → expression of gap and pair-rule genes that pattern the embryo into segments

Question 29

What does Bicoid protein do?

Answer 29

Acts as a transcription factor activating hunchback in the anterior.

Question 30

How does the hunchback gradient form in Drosophila?

Answer 30

Bicoid protein promotes more hunchback expression in the anterior

Question 31

what does the nanos protein do?

Answer 31

supresses nanos in the posterior

Question 32

what is the main reason for cell division being rapid in C. elegans?

Answer 32

no G phases