Animal Development

Question 1

4 stages of Animal Development

Answer 1

1. Fertilization
2. Cleavage
3. Gastrulation
4. Organogenesis
   then growth!

Question 2

Fertilization, Cleavage, Gastrulation, Organogenesis basics

Answer 2

Fertilization - egg and sperm fusion
cleavage - zygote subdividing and determinants partitioned in blastomere (body plan); cell division with no intermediate growth - fast division
gastrulation - germ layers
organogenesis - organs forming, cell interacting and differentiating

Question 3

acrosome and mitochondria in sperm

Answer 3

acrosome: head of sperm; releases digestive enzymes that destroy the jelly layer/zona pellucida for sperm to reach egg
mitochondria: lots of mitochondria, need the energy to move to fertilize

Question 4

jelly layer/zona pellucida in mammals

Answer 4

glycoproteins that release chemoattractants to guide sperm to eggs

Question 5

yolk

Answer 5

nutrients to support growth of developing embryo

Question 6

vitalline envelope

Answer 6

separates the egg from zona pellucida/jelly layer; outside of cell’s plasma membrane

Question 7

cortical granules

Answer 7

vesicles that hold enzymes that will degrade the proteins that hold the vitalline envelope around the plasma membrane when fertilization occurs

Question 8

Events in Fertilization (8)

Answer 8

1. sperm binds to jelly layer
2. initates acrosome reaction - chewing up jelly layer
3. allows sperm-egg membrane fusion (bindin on sperm and bindin receptors n eggs)
4. membrane fusion leads to egg membrane depolarization as a fast block to stop further fusion of sperms
5. depolarization induces Ca2+ wave (triggers formation of fertilization envelope)
6. induces cortical reaction
   7.degrades bindin receptors and bindin proteins on sperm and causes vitelline membrane to lift and form fertilization envelope (slow block)
7. egg activation - egg recognizes fertilizaation has occured - DNA fusion of eggs? and intiates development

Question 9

cleavage cell division

Answer 9

the whole embryo stays the same size, individual cells are getting smaller because its dividing

Question 10

cleavage results in

Answer 10

blastomeres (the actual small cells, mass of cells)
–blastula: when cleavage is completed; embryo of 100+ blastumeres - a spherical layer of blasteomeres considered to be the first embryonic tissue (below)
blastoderm (first tissue) - surrounds a fluid-filled, yolk-filled (below)
blastocoel (first cavity)
establishment of body axes (first division in protostomes and much later in clceavafe for deuterosomes)

Question 11

blastocyst

Answer 11

mammalian blastula; unlike other animals, it has an inner cell mass and outer cell layer (trophoblast) – inner cell mass becomes the embryo and trophoblast will form the embryonic portion of placenta

Question 12

intrinsic vs extrinsic factors in cell specialization

Answer 12

intrinsic - lineage info, inherited from mother cell, present in the cytoplasm of mother cell and therefore cytoplasm of daughter cell: asymettric distribution of these fate-determinant cytoplasmic determinants can have daughter cells with different identities
extrinsic: induction, info from surrounding environment and neighboring cells

Question 13

body axes

Answer 13

all animals except sponges
lateral-medial (left-right)
dorsal-ventral (back-belly)
anterior-posterior (head and feet)

Question 14

cytoplasmic determinants

Answer 14

mostly protosomes/invertebrates
insects - Drosophila embryo!; assymetric distribution after first cleavage - resulting cells have different instrinsic information and different cell fates - highest concentration of bicoid in Drosophila mean head with the lowest becomes the tail/posterior SO future cell identity is set after very first cleavage division
-not mammals!

Question 15

yolk polarity

Answer 15

animals like amphibians, reptiles, birds, fish
-asymmetrical distribution of yolk due to heaviness of yolk - in animals with large amounts of yolk
- region with less yolk becomes head while with the most becomes posterior
by the time the first cleavage comes - already established (left and right)
ventral and dorsal established where sperm entry

Question 16

mammals body plans

Answer 16

uses induction and extrinsic information bc we have less yolk and no cytoplasmic determinants

Question 17

splitting an egg after fertilization

Answer 17

with mammals - get identical twins!
with cytoplasmic determinants/yolk polarity: dividing too early due to the cytoplasmic determinants or yolk polarity - you get different cell fates and embryo fates!!

Question 18

morphogenesis

Answer 18

gastrulation + organogenesis - resulting in organism’s shape and body organization

Question 19

gastrulation results in

Answer 19

gut formation: archenteron (embryonic gut)
embryonic germ layers
APPEARANCE of major body axes - actually becomes visible

Question 20

germ layers - embryonic tissues

Answer 20

endoderm
ectoderm
mesoderm
later differentiate into different tissues and organ systems

Question 21

blastopore

Answer 21

invagination: group of cells move into blastocoel to form the endoderm

Question 22

mesoderm

Answer 22

group of cells that move into the locations between the endo and ectoderm

Question 23

archenteron

Answer 23

endodermal cells continue through interior of embry until it reaches the other side and creates a continuous tract or embryonic gut

Question 24

fate of blastopores in deuterostomes and protostomes

Answer 24

protosomes mouths
deutersomes anus

Question 25

diploplasts vs triploplasts

Answer 25

2 germ layers - radial symmetry and less tissue types vs 3 germ layers

Question 26

germ layers in relation to tissues

Answer 26

ectoderm - nervous system and epidermis mesoderm - muscle cells and connective tissue endoderm - columnar cells in digestive system and internal organs

Question 27

four extra-embryonic membranes from amniotes

Answer 27

germ tissues extend beyond embryo and develop into these amnion, yolk sac, chorion, allantois

Question 28

amnion

Answer 28

membrane surrounding fluid-filled cavity to give an aqueous environment and cushions against mechanical shock; ectoderm

Question 29

yolk sac

Answer 29

provides nutrients and blood vessels for transporting nutrients from yolk to embryo; endoderm

Question 30

chorion

Answer 30

gas exchange between embryo and air; mesoderm

Question 31

allantois

Answer 31

waste disposal and helps chorion with gas exchange; endoderm?

Question 32

extraembryonic membranes in placental mammals

Answer 32

yolk sac and allantois function as part of umbilical cord placenta - provides oxygen and nutrients to a growing baby and removes waste product

Question 33

development in placental animals

Answer 33

fertilization occurs in fallopian tube/oviducts; cleavage occurs while traveling through tube; implantation on uterine wall and gastrulation occurs after implantation

Question 34

organs and tissues

Answer 34

organs made up of 2 or more tissues tissues: groups of similar cells that work together on specific task

Question 35

4 primary types of adult tissues

Answer 35

cells of germ layers will proliferate, migrate, and differentiate into : epithelial tissue connective tiissue muscle tissue nervous tissue

Question 36

epithelial tissues

Answer 36

tightly packed sheets that cover surfaces and form barriers polarized: top and bottom side

Question 37

muscle tissues

Answer 37

contractile tissues that allow movements

Question 38

connective tissues

Answer 38

cells in a extracellular matrix of plasmawith solids, jelly, liquids: adipose tissue (bodyfat),bone cartilage, blood, etc; support and connect other tissues - supports organs and blood vessels - links epithelial tissues to muscles; connecting bones to nuscles

Question 39

nervous tissues

Answer 39

sensory and processing cells that transduce electrical signals or support cells that do neurons and glia cells

Question 40

skeletal, cardiac, and smooth muscle

Answer 40

skeletal is attached to bones and voluntary; cardiac line walls of heart and are involuntary; smooth muscle are walls of blood vessels, digestive tract, uterus, bladder, and other internal structures also involuntary

Question 41

what systems do ectoderm form

Answer 41

nervous system, cornea and lens of eyes, epidermis of skin, epithelial lining of mouth and rectum

Question 42

what systems do mesoderm form

Answer 42

skeletal, circulatory, lymphatic, muscular, excretory, reproductive, dermis of skin, lining of body cavity

Question 43

endoderm derived systems

Answer 43

epithelial lining of digestive tract, respiratory, reproductive, urinary tract - liver, pancreas, parathyroids, thymus?

Question 44

5 essential developmental processes

Answer 44

1. proliferation 2. programmed cell death 3. cell movement and differential expansion 4. differentiation - cell type specific changes in gene expression 5. induction - cell cell communication which mediates basically all other developmental processes

Question 45

epigenetics

Answer 45

how cell differentiation occurs - differences in cell types are result of expression of different genes even tho all cells share the same genome

Question 46

cell differentiation - asymmetry

Answer 46

1. during cleavage divisions, embryonic cells become different from one another if egg contains cytoplasmic determinants - cytoplasm is heterogenous (not uniform) 2. after cell asymmetries are set up, interactions among embryonic cells can influence fate and change gene expression: induction!

Question 47

example of organogenesis: formation of the nervous system

Answer 47

notocord forms: signals the ectoderm to fold (thicken and move to become) into a neural tube which becomes the spinal cord and brain while the notochord will disappear and become spongy discs in the vertebrae

Question 48

somites

Answer 48

from the mesoderm; lies on either side of the vertebrate neural tube; temporary structures later development: migrate to different parts of the body to develop into bone, skeletal muscle, and connective tissue; specific pattern of induction from nearby tissues from ectodern, neural tube, notochord. surrounding mesoderm --> determines what tissue a particular region a somite will become

Question 49

morphogenesis

Answer 49

differential gene expression

Question 50

morphogens and cytoplasmic determinants with regulatory genes

Answer 50

in a concentration gradient of drosophila embryos - cytoplasmic determinants that establishes anterior-posterior gradient? cytoplasmic determinants are often regulatory genes? that direct expression of other genes - developmental "cascade" leading to proper development of animal regulatory genes regulatory genes that organize cells into groups along segments; which regulate genes that organize cells into individual segments, which regulate genes that establish anterior-posterior in each segment which triggers the Hox genes which trigger the development of structures which effect the effector genes (cell death, movement, differentiation)

Question 51

Homeobox or Hox genes

Answer 51

type of regulatory genes; regulate gene expression by binding to DNA control regions like promoters and enhancers encode transcription factors -family of genes responsible for determining general body plan like number of body segments -- each body segment is specificed by a specific comibation of Hox genes (segment identity!!) where other different body parts then develop -all animals except sponges have this -plants relu on Mads box (not evolutionary related) -control identity of body parts "head architects" - have other lower tier genes for more specific instructions

Question 52

transcription factors

Answer 52

if transcription factors attach to regulatory element: go for the transcription of that set of genome? so Hox genes make those transcription factors

Question 53

misexpression hox genes

Answer 53

segments can take on new identities misexpression of Ubx - lead to extra wings of Antp: legs in new places - in segments its not supposed to be

Question 54

Hox genes in tetrapods and in segment identity

Answer 54

for tetrapods with forelimbs, certain combinations of hox genes will lead to different body parts compared to just one hox gene by itself

Question 55

duplication of Hox cluster

Answer 55

occurred in more than 2x in vertebrates during animal evolution - more genes mean more complex body types

Question 56

Hox genes homology

Answer 56

homologous in animal kingdom, genetic sequences and positions on chromosomes are remarably similar across most animals

Question 57

instructions of hox genes

Answer 57

"make something here" not HOW -- passes the instruction to other regulatory genes which then make that animal's version of that body part