Development

Question 1

What are the key features of fertilization ?

Answer 1

Recognition at a distance, contact recognition and binding, egg and sperm fusion, blocks to polyspermy, egg activation

Question 2

What is the resact in context of sea urchin

Answer 2

Soluble glycoprotein derived from the jelly layer of the egg

Question 3

Define chemotaxis

Answer 3

The migration of cells towards a soluble concentration gradient of a stimulant

Question 4

Define acrosomal reaction

Answer 4

The acrosomal vesicle fuses with the plasma membrane causing the extracellular release of digestive enzymes that penetrate the jelly coat

Question 5

Define bindin

Answer 5

Protein molecule on the acrosomal membrane that binds with the species specificity to the vitelline layer of the egg

Question 6

What happens in the fast transient block to polyspermy

Answer 6

Membrane depolarization, rapid change in the egg plasma membrane potential caused by increase in Na+ concentration

Question 7

What happens during the cortical reaction/ slow block to polyspermy

Answer 7

Triggered by intracellular calcium release which causes cortical granules to fuse with the memebrane

Question 8

Describe the early and late events in egg activation

Answer 8

Early events - increase in cell metabolism
Late events- initiation of protein and DNA synthesis in preparation of first clevage

Question 9

Define zona pellucida

Answer 9

Extracellular matrix of the egg

Question 10

Define capacitation

Answer 10

Process by which the glycoprotein coat and the seminal proteins are removed from the surface of the sperm’s acrosome by substances secreted by the uterus or fallopian tubes
-inc sperm metabolism and motility
-necessary for future sperm and egg binding
-triggered by bicarbonate ions in vagina
-requires 5-6 hours in humans

Question 11

Define cleavage

Answer 11

First stage of early embryonic development after fertilization characterized by a series of Mitotically cell divisions
Cell division with no significant growth producing a cluster of cells that is the same size as the original zygote
Cleavage partitions the embryo into smaller cells called blastomeres

Question 12

Define a blastula

Answer 12

Produced after 5-7 cleavage divisions
Consists of a hollow ball of cells with a fluid filled cavity (or blastocoel)

Question 13

Define cleavage furrow in context of frog embryo

Answer 13

Indentation on the surface of the developing embryo

Question 14

Define holoblastic

Answer 14

Cleavage furrow passes entirely through the egg ( frogs, mammals)

Question 15

Define Meroblastic

Answer 15

So much yolk that cleavage furrow does not pass through the yolk portion of the embryo. Cell divisions occurs in a small area ( birds, fish, reptiles)

Question 16

Describe Gastrulation

Answer 16

During gastrulation, cell movements result in a massive reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism

Question 17

Describe the ectoderm

Answer 17

Outer layer of embryo
Epidermis of skin and it’s derivatives
Nervous and sensory systems

Question 18

Describe the mesoderm

Answer 18

Middle layer of embryo
Skeletal and muscular systems
Circulatory and lymphatic systems
Excretory and reproductive systems
Dermis of skin

Question 19

Describe endoderm

Answer 19

Inner layer of embryo
Is epithelial lining of digestive tract and associated organs

Question 20

Gastrulation involves changes in

Answer 20

Cell motility, shape and adhesion

Question 21

What are the six major types of cell movements that occur during gastrulation

Answer 21

Invagination: a sheet of cells (called an epithelial sheet) bends inward
Ingression: individual cells leave an epithelial sheet and become freely migrating mesenchyme cells
Involution: an epithelial sheet rolls inward to form an underlying layer
Epiboly: a sheet of cells spreads by thinning
Intercalation: rows of cells move between one another, creating an array of cells that is longer (in one or more dimensions) but thinner
Convergent Extension: rows of cells intercalate but the intercalation is highly directional

Question 22

Define neurulation

Answer 22

The process of the neural tube formation

Question 23

What are some mechanisms underlying development?

Answer 23

1. Cytoplasmic determinants: maternal substances in the egg that influence the course of early development
2. Signaling molecules from neighboring cells

Question 24

Describe cell fate

Answer 24

Cells makes developmental decisions by responding to signals in their internal local environment
Cells makes developmental decisions within a temporal and spatial framework

Question 25

Define pattern formation

Answer 25

The development of a spatial organization in which the tissues and organs of an organism are all in the right place
Often involves morphogenic gradients

Question 26

Define a morphogen

Answer 26

A substance governing the pattern of tissue development and the positions of the various specialized cells types within a tissue

Question 27

Define hox genes

Answer 27

Homeobox, transcription factors; specify the limb field or pre-pattern

Question 28

What is FGF

Answer 28

Fibroblast growth factor , from AER cells for limb outgrowth

Question 29

SHH

Answer 29

Sonic hedgehog, secreted signaling molecule, from ZPA, involved in A/P patterning, specifies digits

Question 30

How does recognition at a distance work with sea urchins?

Answer 30

The resact is released from the jelly layer into the surrounding seawater. Sperm recognize and bind resact (species-specific) and swim in the direction fo the higher resact concentration(chemotaxis)

Question 31

How does contact recognition work with sea urchins?

Answer 31

Facilitated by a carbohydrate molecule in egg jelly layer binding to a receptor on sperm plasma membrane

Question 32

Give the general steps of fertilization

Answer 32

1) Contact. The sperm contacts the egg’s jelly coat, triggering exocytosis of the sperm’s acrosome
2) Acrosomal reaction
3) Contact and fusion of sperm and egg membranes
4) Cortical Reaction
5) entry of sperm nucleus

Question 33

The zona pellucida is composed of 3 proteins….. sperm plasma membrane receptors bind to….

Answer 33

ZP1, ZP2, ZP3… bind to ZP3

Question 34

Regarding cleavage in the sea urchin which pole is the region where yolk (nutrients) are concentrated?

Answer 34

The vegetal pole.
The animal pole is opposite of the vegetal pole.

Question 35

What is amnion?

Answer 35

membrane that makes the amniotic sac; protection/cushion

Question 36

What is allantois?

Answer 36

sac-like structure, involved in nutrition and excretion, webbed with blood vessels, collects liquid waste from the embryo, and exchanges gases used by the embryo

Question 37

What are the three layers the placenta is composed of?

Answer 37

amnion: intermost placental layer surrounding the fetus
allantois: the middle layer of the placenta
chorion: outermost layer of the placenta, comes into contact with the endomentrium

Question 38

What are the two main organizing region in the limb bud?

Answer 38

AER: apical ectodermal ridge
ZPA: zone of polarizing activity

Question 39

Describe AER

Answer 39

Consist of a thickened region of ectoderm at the tip of the bud involved in proximal-distal organization
cells in AER secrete proteins in the FGF(fibroblast growth factor) that promote and maintain limb bud outgrowth

Question 40

Describe ZPA

Answer 40

mesodermal tissue located where the posterior side of the bud is attached to the body
Organizes the A/P axis; indicates “posterior”
Cells nearest to the ZPA give rise to posterior structures(outer digit); farthest to anterior structures(thumb)
ZPA cells secrete sonic hedgehog (SHH)