Study Questions 3-4

Question 1

When are A-P and D-V axes specified during Drosophilia development

Answer 1

Determined during oogenesis, before fertilization

Question 2

When are A-P and D-V axes specified during C.elegans developent

Answer 2

a-p axis is determine by site of sperm entry and d-v axis by formation of AB found cells

Question 3

What is the difference between the two different types of blastoderm formed during drosophilia development

Answer 3

syncytical blastoderm- all nuclei contained in common cytloplasm
cellular blastoderm- all the cells are arranged in a single layerd jacket around yolky core of the egg

Question 4

what are the types of genes invovled in determination of anterior-posterior axis in drosophillia

Answer 4

bicoid- fucntions as a transcription factor to activate anterior specific gap genes (hunchback)and a repressor to suppress posterior specific gap genes(caudal)
nanos- block translation of hunchback and upregulates caudal

Question 5

What are the bicoid and nanos mRNAs produced during drosophilia oogenesis and where are the localized

Answer 5

Produced and secreted by nurse cell
Bicoid mRNA localized in anterior and nano mRNA
Nanos mRNA secreted by posterior ovarian nurse cells localized to posterior

Question 6

What are the major posterior determinants in early drosophila development

Answer 6

Nanos and caudal

Question 7

Define homeotic genes

Answer 7

act as selectors- activate the construction of segment-specifc traits like wings and legs

Question 8

How is the dorsal-ventral polarity determined in the Xenopus embryo

Answer 8

sperm entry determines dorsal-ventral axis, which is liked to anterior-posterior axis determination

Question 9

What are the two most important purposes of the balstocoel?

Answer 9

Permits cell migration during gastrulation and prevents early cell-cell interactions

Question 10

Define regulative development

Answer 10

celld develop based on their locations in the embryo

Question 11

define autonomous development

Answer 11

determination of cell fate acquired by cleavage, indepedent of interactions with neigbouring cells

Question 12

Define Dorsal blastopore lip

Answer 12

location of the involuting marginal zone cells of amphibian gastrulation, acts as the center of differentiation

Question 13

define spemann’s organizer

Answer 13

the dorsal lip cells of the blastopore and its derivatives (pretty much the same as blastopore lip), induces development of the nervous system

Question 14

Define Nieuwkoop center

Answer 14

doral most vegetal blastomeres of xenopus blastula, induces the spemanns organizer

Question 15

What is b-canenin

Answer 15

A transcription factor and important in specifying Nieuwkoop center

Question 16

How does the amount of yolk influence cleavage in birds?

Answer 16

Discoidal meroblastic cleavage, embryo forms a blastodisc on top of the yolk
Have teloecithal egg cells, with the yolk concentrated at one end

Question 17

Define primitive streak

Answer 17

formed by cells accumulating in the middle of the bird embryo, undergoes convergent extension

Question 18

Define primitive groove

Answer 18

depression forms in the primitve streak and migrating cells pass through

Question 19

Define hensens node

Answer 19

a funnel which migrating cells pass into the blastocoel, first site of gastrulation and located at the anterior of the primitive streak, analog spemanns organizer, IN AMPHIBIANS!

Question 20

What are the first cells which are passing thorugh the primitive streak during gastrulation

Answer 20

endodermal precursors, undergo a transformation as the streak elongates towards the head

Question 21

What is the chicken equivalent to the Xenopus Spemann organizer

Answer 21

Hensens node

Question 22

What is the chicken equivalent to the amphibian blastopore lip?

Answer 22

PMZ, posterior marginal zone

Question 23

What are the five characteristics of mammalian early cleavage?

Answer 23

1) division very slow
2) orientation of blastomere cleavage varies, second cleavage undergoes rotational cleavage
3) division are not necessarily synchronic
4) mammalian genome activated early in cleavage
5) compaction when the blastomeres huddle together

Question 24

Define blastocyst

Answer 24

mammalian analog of the blastula

Question 25

What is the role of trophoblast during embryonic implatnation

Answer 25

Role is to contribute to the further digesion of the uterus and formation of the placenta

Question 26

What is the chorion

Answer 26

the embryonic portion of the placenta

Question 27

What is formed during the first segregation of ICM? What is this structure called?

Answer 27

The hypoblast and epiblast, form the bilaminar germ disk.

Question 28

What part of the bilaminar germ disk will develop into the embryo properly?

Answer 28

The epiblast