Quiz 1 flash cards

BIL 455 quiz 1 Dr. Wikramanayake

fundamental questions of developmental biology

1. how does a fertilized egg give rise to an adult body

2. how does that adult body produce another body

major objectives accomplished by development

1. generates cellular diversity and order

2. ensures continuity of life from generation to generation

why is developmental biology important

it explains how a fertilized egg becomes an embryo, juvenile, and adult, and how tissues are maintained, repaired, and produce future generations

pattern formation

the process by which cells aquire positional information and are arranged correctly in a body plan

differentiation

the process by which cells become specialized for particular functions

pattern formation, differentiation, and morphogenesis

• pattern formation → where cells belong

• differentiation → what cells become

• morphogenesis → how tissues and organs are physically shaped and arranged

why use model organisms

different organisms are best suited for answering different biological questions

characteristics of good model organisms

• small size

• short generation time

• accessible embryos

• genetic manipulability

• ability to do forward and/or reverse genetic studies

• organism type and phylogenetic position

• ease of experimental manipulation

• low cost

major categories of questions addressed in developmental biology

• pattern formation

• differentiation

• morphogenesis

• growth

• reproduction

• human development

• regeneration, stem cells, and synthetic developmental biology

• environmental integration

• evolution

August Krogh

1874-1949 emphasized the importance of organism choice for experimentation

Krogh principle

there will always be an animal of choice that can be most conveniently studied (1929)

post-fertilization developmental stages

fertilization → cleavage → blastula → gastrulation → organogenesis

major fertilization events

1. fusion of the sperm pronucleus to the egg pronucleus

2. leads to metabolic activation of the egg (egg activation)

3. rearrangement of the egg cytoplasm occurs

characteristics of cleavage

1. cell division occurs, often very rapidly

2. cell cycle is altered and lacks G phases

3. there is no growth

4. there is little visible specialization of cells

what is a morula

early embryo before it reaches the blastula stage

characteristics of a blastula

1. contains several hundred to several thousand cells

2. shows little specialization of cells

3. consists of a polarized epithelium surrounding a blastocoel cavityy

4. is one of a few cells thick

5. contains cells called blastomeres

6. cell division slows

7. in many embryos, new gene expression from the embryonic genome begins

MBT and MZT

the transition during blastula stage when new gene expression from embryonic genome begins and developmental control shifts from maternal products to zygotic gene expression

animal-vegetal axis

• primary axis of the egg

• generally defined by the position of the polar body release during meiosis

• derived from apical-basal epithelial polarity

• contribute to anterior structures and vegetal pole derived cells contribute to posterior structures

significance of vegetal pole in bilaterian embryos

endoderm and mesoderm (endomesoderm) form at the vegetal pole

how is the egg asymmetric along the animal-vegetal axis

is asymmetric with respect to structure, molecules, developmental potential, and the fates of blastomeres that inherit different regions of the cytoplasm

how is dorsal-ventral axis esteblished in amphibians

not initially fixed and is formed epigenetically by an external signal, specifically the sperm entry point, through cortical rotation of the amphibian egg

major gastrulation events

1. tissue movements create a “tube within a tube”

2. the archenteron (primitive gut) forms

3. primary germ layers are established

4. major body organization begins

archenteron

primitive gut formed during gastrulation and represents the inner tube in the “tube within a tube” body plan

primary germ layers

1. endoderm

2. mesoderm

3. ectoderm

derivatives of endoderm

1. gut

2. lungs

3. functional parts of associated organs like liver and pancreas

derivatives of mesoderm

1. bone

2. muscle

3. blood

derivatives of ectoderm

1. skin

2. central nervous system

blastopore in deuterostomes

becomes anus, second opening later forms mouth which is why it is called deuterostome

cell movement during gastrulation

embryos use a combination of different cellular movement mechanisms during gastrulation to reposition cells and establish the body plan

organogenesis

stage during organs form through interactions among cells, most often from different germ layers, frequently involving differential growth and utilization of stored yolk

earliest important structures formed during vertebrate organogenesis

1. notochord

2. overlying neural tube

neurula

embryo in which the neural plate has formed

neural tube formation

result of neural plate folding inward

morphogenesis

process by which cells, tissues, and organs are arranged into correct 3-dimensional relationships and forms within the embryo

in what coordinate system does morphogenesis occur

occurs within a three-dimensional coordinate system established by embryonic axes

questions of embryonic axes

1. where does the information come from to establish embryonic axis

2. what kinds of gene products construct an axis

epithelial cells

cells that are tightly connected to one another and typically form organized sheets

mesenchymal cells

cells that usually migrate individually and are not tightly connected to neighboring cells

fate map

identifies which regions of an embryo ultimately give rise to specific cells, tissues, and structures in the larva or adult organism

cell lineage

developmental history of cells showing how descendant cells arise from earlier embryonic cells and what structures they eventually produce

fate map constuction techniques

1. vital dye staining

2. fluorescent dye labeling

3. GFP-based lineage traving using transgenic animals expressing green fluorescent protein

tissue transplantation utilization in lineage studies

researchers can distinguish transplanted chick cells from quail cells using nuclear morphology or genetic markers and then follow the descendants of those transplanted cells

how is pattern formation related to morphogenesis

closely related to morphogenesis because it regulates both the destinies of cells and their 3-dimensional arrangement within larger structures

at what levels can pattern formation be studied

1. whole body organization

2. body parts

3. localized patterns such as color patterns on butterfly wings

how does growth contribute to morphogenesis

differential growth is one of the mechanisms underlying morphogenesis and helps shape tissues and organs during development

how is cell cycle regulation related to development

remaining in the cell cycle or withdrawing from it is a critical aspect of determination and differentiation during development

how is cancer related to developmental biology

cancer develops when cells acquire uncontrolled growth resulting from abnormal functioning genes that normally regulate growth and division during development

hippo pathway

a signaling pathway that regulates organ size in animals

co-option

process by which a structure is converted to an entirely different use from its original function

homologous structures

structures derived from a common ancestral structure but do not necessarily perfomr the same functionan

analogous structures

structures that have similar functions but do not share the same evolutionary origin

molecular homology in developmental biology

molecular pathways are highly conserved across animals and these similarities can be used to understand development and evolutionary relationships

why are model organisms used for understanding human development

bc developmental pathways are often highly conserved researchers can use organisms that are most experimantally tractable to learn about the developmental mechanisms that also operate in humans

Evo-Devo

field that studies how developmental mechanisms evolve and how developmental processes influence evolutionary change

why are sperm and eggs important

highly specialized cells that ensure transmission of biological information to the next generation

developmental biology reproduction questions

1. how are sperm and eggs set apart from from the next generation

2. what instructions within the nucleus and cytoplasm allow these cells to function as reproductive cells

environmental integration

examines how developmental processes are influenced by cues from the environment and is sometimes discussed as EcoEvoDevo

toxicology and teratology

examine situations in which embryos cannot properly cope with environmental influences resulting in abnormal development such as malformed frogs or fetal alcohol syndrome

regeneration

ability of an organism to replace lost cells, tissues, or structures after injury

stem cells

cells that replenish tissues and have the capacity to generate new specialized structures and cell types

induced pluripotent stem cells (IPSCs)

1. reprogrammed cells with the potential to produce many kinds of cells, tissues, and organs

2. have potential applications in transplantation and regenerative medicine

why are some movements during gastrulation important

1. they reposition cells from outside of embryo to correct locations within embryo

2. allow formation of germ layers and establishment of body plan

3. most embryos use a combination of several gastulation mechanisms rather than a single movement type

gastrulation major cell movement types

1. invagination

2. involution

3. ingression

4. delamination

5. epiboly

invagination

1. a sheet of cells bend inward as a unit producing an inward pocket/indentation in the embryo

2. contributes to the formation of internal structures like primitive gut

involution

1. layer of cells rolls inward over an edge then spreads along the inner surface of the embryo

2. cells move into the embryo while remaining part of continuous sheet

ingression

individual cells leave epithelial sheet and migrate independently into the interior of the embryo as mesenchymal cells

delamination

one sheet of cells splits into two parallel sheets, creating separate layers of cells

epiboly

sheet of cells spreads and expands to cover a larger surface area, often surrounding deeper layers of the embryo