Lecture 2 - Animal Devlopment

Question 1

Morphogenesis

Answer 1

Occurs via changes in cell position, shape, survival, and form of organs
- rearrangement of cells or sheets

Question 2

Fertilization

Answer 2

Haploid gametes join to form a diploid zygote

Question 3

Model Organisms

Answer 3

Easy to study but broadly representative
- Development al genes and mechanisms are similar across animal species
-Studying development in model organisms provides knowledge about development in general

Question 4

Gametes in sea urchins

Answer 4

Sperm and egg are the haploid gametes
-Egg cytoplasm contains many proteins and mRNA involved in early development

Question 5

Fertilization in sea urchins - step 1

Answer 5

Sperm contact with the jelly coat triggers the acrosomal reactions
- This is what allows the sperm to reach the egg - the kind of softening of the egg

Question 6

Differential Gene Expression

Answer 6

Foundation of diverse cell types and behaviors through development

Question 7

Fertilization in sea urchins - step 2

Answer 7

Surface proteins on acrosomal process bind to receptors on egg cell membrane

Question 8

Fertilization in sea urchins - step 3

Answer 8

Plasma membrane fuse, triggering fast block to polyspermy
- polyspermy - the oocyte is penetrated by more than one sperm
-fast block is a reversal of polarization to repel the other sperm

Question 9

Fertilization in sea urchins - step 4

Answer 9

The sperm nucleus enters and the cortical reaction causes a slow block to polyspermy
-Perivitelline space occurs - a physical separation from the outside and inside of the egg, this is the slow block

Question 10

Fertilization in sea urchins - step 5

Answer 10

Fusion of sperm and egg nuclei form the diploid nucleus of the zygote - there is a small clear envelope around the zygote called the fertilization envelope

Question 11

Cleavage

Answer 11

-the process by which the zygote becomes multicellular
-Rapid cell division with little growth of individual cells
(G1 and G2 phases
skipped)
-results in blastomeres

Question 12

Blastomeres

Answer 12

smaller cells resulting from cleavage

Question 13

What does cleavage result in?

Answer 13

-Cells getting smaller and smaller with each round of division
- No growth of cells between divisions

Question 14

In frogs

Answer 14

Zygote becomes a blastula

Question 15

Blastula

Answer 15

A hollow ball of cells with a fluid-filled cavity called the blastocoel
-There is an animal pole and a vegetal pole
- where sperm hits the egg becomes the animal pole (smaller cells, less ‘yolky’)

Question 16

Differential gene expression

Answer 16

• cells express different genes depending on their location and the stage of development
• expressing different genes leads to the production of different proteins (this, in turn, determines the structure and behaviors of the cell at any given time)

Question 17

Cytoplasmic determinants

Answer 17

A signal given within the cell determines how the gene is expressed
-molecules within the cytoplasm regulate gene expression
- can be differently distributed to daughter cells resulting in differences in gene expression

Question 18

Inductive signals

Answer 18

A signal from outside of the cell determines how the gene is expressed
-The signal molecules that a cell is exposed to depends on its location within the embryo, and the stage of development

Question 19

Embryotic stages - Cleavage

Answer 19

converts the unicellular zygote into a multicellular embryo

Question 20

Embryotic stages - Blastula

Answer 20

a hollow ball of cells

Question 21

Embryotic stages - Gastrulation

Answer 21

where the three germ layers are formed

Question 22

Gastrulation

Answer 22

Stages when the three germ layers are established and the basic body plan is set up
-Results in a three-layered gastrula

Question 23

Organogenesis

Answer 23

formation of the organs

Question 24

neurlation

Answer 24

formation of the nervous system
- is an example of organogenesis

Question 25

Three layers of gastrula

Answer 25

ectoderm, mesoderm, endoderm

Question 26

Frog gastrulation - step 1

Answer 26

Cells in the vegetal hemisphere push inwards

Question 27

Frog gastrulation - step 2

Answer 27

outer cells (future endoderm and mesoderm) roll inwards

Question 28

Frog gastrulation - step 3

Answer 28

Blastocoel collapses and a new cavity - archenteron is formed

Question 29

Frog gastrulation - step 4

Answer 29

Cells at the animal pole (future ectoderm) spread over the outer surface

Question 30

Convergent extension

Answer 30

example of cells changing their position
- produces a longer, narrower structure
- an example of morphogenesis

Question 31

ectoderm

Answer 31

will form the skin, nervous system, and sense organs

Question 32

mesoderm

Answer 32

will form the skeleton, muscles, and hearts

Question 33

endoderm

Answer 33

Will form the digestive system and respiratory tube

Question 34

Formation of the neural tube - step 1

Answer 34

Ectodermal cells change shape during neural tube formation

Question 35

Programed cell death

Answer 35

-Changes the shape of the embryo