lec 1: Developmental biology introduction

Question 1

What is developmetal biology AND embroloygy

Answer 1

-studies all processes relating to how a multicellular organism forms from a single cell and HOW THAT ORGANISM:
-maintains tissue homeostasis *stem cells and regeneration
-adapts to environment
-produces other single cells that propogate the species
-ages
-evolves as a species

Question 2

Why study development

Answer 2

-to understand how and why it goes wrong sometimes (birth defects, cancers being return of processes needed for development
-to answer the question of how a dividing cell can generate two daughter cells that are different
-if most euk genome is similar how does it make organisms that are vastly different

Question 3

Big questions of developmental biology according to gilbert

Answer 3

How does the fertilized egg give rise to the adult body and how does the adult body make another adult body

Question 4

What are the different categories we are questioning and the questions

Answer 4

Differentiation:
Mammals have less than 200 cell types but each carry the same set of genes. How does one cell give rise to such different cell types (stem cell to rest)

Morphogenesis:
How do the different cells organize themselves into functioning structures?
-ie how is everythign coordinated (cell death, migration, division) so that things form at the right place at the right time (ie toes)
ex: Syndactyly: failure of programmed cell death in the developmental of toes

Growth:
How do our cells know when to stop dividing
-animal bodies are symmetricall equally and proportioned, how?

Reproduction:
Only sperm and egg transmit genetic info to the next gen. How are they set aside from the rest of the embryo and what instructions do they recieve that tells them that they are the germ line?

Regeneration:
Some organisms can regenerate body parts or parts of them following injury. Stem cells retain the ability to form new structues-
-so how are stem cells different from other somatic cells and can we trate human diseaess using stem cell

Evolution:
Evolution involved inherited changes in development. Slight or dramatic changes in body plan may arise through random mutation. If it is an advantage, it will spread through the speices through natural selection.
-How do changes in development result in new body forms? To what extent can this occur without causing embryonic lethality
-what developmental restrains are there in terms of new body plans

Environmental integration:
Development is influenced by environment (phenotype), ie croc sex is determined by termperature
-how is development influenced by an organisms environment

Question 5

What is Syndactyly

Answer 5

-failure of programmed cell death to develop digits
frequency: 1/2000 - 2500 people

Question 5

What is an example of environmental integration

Answer 5

Caterpillars of moths (Nemoria Arizonia) exhibit different phenotypes based on their diet.
-Caterpillars that feed on oak flowers resemble flowers whereas those that fed on leaves resemble twigs

Question 5

What are the two perspectives that aristotle had for cleavage (two different types of cleavage)

Answer 5

1) Holoblastic:
-“holos” means complete
-refers to cell division (cleavage) pattern in the EMBRYO where the entire egg is divided into smaller cells (as in frogs and mammals)

2) Meroblastic:
-“meros” means part
-cleavage pattern in ZYGOTES with large amounts of yolk where only a PORTION of cytoplasm is divided
-this is bc the cleavage furrow does not penetrate the yolky portion bc this part impedes membrane formation thereofre only part of the egg is meant to be the embryo while the YOLK serves as nutrition for the embryo
-similar to insects, fish, reptiles, birds

Question 5

What was william harvey’s perspective

Answer 5

” Ex Ovo Omnia”
-all animals, even viviparous animals (meaning give birth to young live, dont lay eggs) originate from eggs
-first to suggest that humans and other mammals reproduced via the fertilation of an egg by sperm. Took nearly two centuries before a mammalian egg was examined
-DID NOT USE MICROSCOPE
-he was interested in the blood and circulatory system
-notices that blood tissue forms before the heart and examined blastoderm in chick

Question 6

What is development SUMMARY definitino

Answer 6

The process of progressive and continous change that generates a complex multicellular organism from a single cell
-it occurs throughout embryogenesis, maturation to adult frorm and continues into senescence (procress of deterioation through age)

Question 7

What is viviparous

Answer 7

give birth to living young, do not lay eggs

Question 8

Cells are 1/5 the size of the smallest particle visble to eye

Answer 8

true
also colourless and translucent
average euk cell has a diameter of 10-20 um

Question 9

When did the cell doctrine come out and what was it

Answer 9

the idea that all plant and animal tissue arises from cells
happened when the modern light microscope came out

Question 10

What did marcella malpighi see

Answer 10

the neural groove: precursor to the nerual tube
somites: muscle forming
arteries and veines: to and from the yolk

Question 11

Epigenesis vs preformation

Answer 11

Epigenesis:
-idea that organs of embryo are formed from scratch
-it develops from the fertilized egg into a organism through gradual formation of new structures
-theory of embryogenesis
-developed from aristotle and harvey (whilst examining chick embro)

Preformation:
-concluded that organs were present in miniature form
-by malpighi
-makes no sense bc he used a microscope but this theory was very prevalent probably due to religion

Question 12

How was epigenesis established

Answer 12

Christian pander, karl ernst, heinrich rathke
-better microscopes and stins
-described germ layers
-discovery of notochord
-discovery of mammalian egg
-concept of induction (tissues construct organs through interactions with other tissues)

Question 12

What was kaspar friedrich wolffs view

Answer 12

-chick embryonic parts develop from tissues that have no recognizable adult counterpart
-heart and blood vessels seen to develop anew
-intestinal tube formation observed as folding of what was originally a flat tissue

-supports epigenesis but w/o the concept of cells and cell doctorine

Question 13

What is the notochord

Answer 13

• a transient mesodermal rod in the most dorsal portion embryo that plays an important role in inducing and pattering the nervous system

Question 14

Karl ernst von baer what did he do

Answer 14

-comparitive embryology
-made von Baer Laws- which were a set of generalizations that argued against the flawed view of recapitulation

Question 15

What is recaptulation

Answer 15

-idea that ontogeny (growth and developemt) occurs through a variety of stages that are representative of the evolutionary phylogeny of a particular species
-ie, people who believed in this would say that when u were an embryo u were a fish, then a newt, then a lizard, then a chicken then an organguatn until u developed the fearures of human

Question 16

What were the karl von baer laws

Answer 16

-set of generatlizations that were made to show that recapitualition was flawed

1) all embryos go through a similar stage
2) generatlized features appear in early developemnt
3) specialized features arise from generalized ones
4) adult forms of lower animals are not embryos of higher animals

Question 17

Shwann and Schleiden view

Answer 17

Cell theory: all liviing things are built of cells
-virchow added that cells are derived from preexisting cells (these two thtough that they arose spontaneously)

Question 18

Late 1800s perspective

Answer 18

-cell theory was established
-early embryologists founf that cells do not remain in one place or maintain the same shape in embryos
-difference between epithelial cells (surface cells) and mesenchymal cells (cells that can go into muscle, bone cells, etc) was recognized

Question 19

What are the steps of generalized lifecycle?

Answer 19

1) fertilization
2)cleavage
3)gastrulation
4) organogenesis
5) metamorphosis
6) gametogenesis

Question 20

What is fertilization stage

Answer 20

-fusion of male and female gamete, then a fusion of haploid gamete nuclei to restore the full complement of chromosome characteristics of the species and initiation in the egg cytoplasm of those reactions that permit development to proceed

Question 21

What is a gamete and a genome and karyotype and heterogametic chrmosomes

Answer 21

Gamete: specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring (haploid cell that is involved in fertilzation)

Genome: complete dna sequence of an individual organism

karyotype:
complete set of chromosomes of an organism that is displaced systematically

Heterogametic:
xy -produce two different gametes
xx-homogametic

Question 22

What is the second step of generalized lifecycle and explain

Answer 22

Cleavage
-series of rapid mitotic cell divisions following fertilizatoon in many early embryos
-divides embryo WITHOUT increasing mass
(gets smaller and smaller cells)
-creates blastomere (cleavage stage cell resulting from mitossi

Question 23

What is a blastomere vs morula vs blastula va blastoderm

Answer 23

Blastomere: a cleavage stage cell resulting from mitosis

Morula: vertebrae embryo of 16-64 cells, precedes blastula or blastocyst stage

Blastula: early stage embryo with sphere of cells surrounding an inner fluid filled cavity called the blastocoel

Blastoderm: single layer stage before and during gasturlation

Question 24

What introduces the blastocoel

Answer 24

catation indroduces the blastocoel: fluild filled cavity

Question 25

What is gastrulation

Answer 25

3rd stage of life cycle

-process involving movement of the blastomeres of the embryo relative to one another resulting in the formation of the three germ layers of the embryo
-contains the process that amkes the germ layers too
-most important time in our life

Question 26

What is a gastrula

Answer 26

stage of the embryo following gastrulation that contains the three germ layers that will interact to generate the organs of the body

Question 27

What is the formation in gastrulation and what is moving

Answer 27

formation of three germ layers : endoderm, mesoderm adn ectroderm

moving: blastomeres relative to one another

Question 28

What is a zygote vs embryo

Answer 28

fertilized egg with diploid chromosome complement in its nucleus, generated by fusion of haploid male and female pronuclei

embryo: a developing organism prior to birth or hatching (in mammals used to describe the point from fertilization to end of organogensis, aftr its called a fetus)

Question 29

Germ layer and types

Answer 29

-on of the three layers of embryo
-germ layers will form the tissues of the body except for the germ cells

a) Ectoderm: outside, cells that are on outside or dorsal surface of embryo
-forms nervous system from neural tube and neural crest and generates EPIDERMIS covering embryo
-even neurons in brain dervie from ectoderm

b)Endoderm: within, innermost germ layer, forms the epithelial lining of the respiratory tract, the gastrointestinal tract, and the accessory organs (liver, pancrease) of digestion tract
-whereever invagination is

c)mesoderm: between, in middle of others, gives rise to muscles, skeleton, connective tissue, reproductive organs, kidney, blood and cardiovascular system

Question 30

Triplobastic vs diplo

Answer 30

have three layers or two (bc lack a mesoderm)

Question 31

Organogenesis

Answer 31

4th stage

-interactions between and rearrangement of cells of germ layers to produce tissues and organs
-some move far to get to where they need to be
ex: skin is epidermis + dermis
epidermis dervices rom ectoderm, dermis derives from mesoderm

Question 32

Metamorphosis

Answer 32

5th stage
-changing from one form to another, ie larvae to butterfly

Question 33

Gametogenesis

Answer 33

-production of gametes

1st meiotic divison: reductional. haploid replication
2nd: equational

Question 34

germline cells vs somatic cells

Answer 34

Germline: group of cells set aside from the somatic cells for reproductive function
-consists of cells of the gonads (ovaries and testes) that undergo meiotic divison to make gametes (sperm adn egg)

Somatic cells:
body cells, cells that form the body, anything that isnt germline

difference between these two is one of the first differentiations that occurs during animal development

Question 35

epithelial cells vs mesenchymal cells

Answer 35

epithelial:
-form barrier sheets connected by junction complex
-move together
-basal lamina is a foundaction, contacts only one surface of cell

Mesenchymal:
-loosely organized and loosely attached cells
-can move individually bc loosely attached
-can stick in 3d clumps
-basal lamina may surround cells (muscle or fat)

Question 36

What are some cellular processes that coordinate the organization of cells into functional structures

Answer 36

Morphogenesis: The organization of the cells of the body into functional structures via coordinated cellular processes such as:

cell movement or migration
cell growth – some cells become smaller (sperm cells) or larger (egg cells)
cell death – programmed removal of superfluous cells or entire tissues
cell division – direction and amount of
cell shape changes (can also involve change in character from epithelial to mesenchymal – also occurs as cancer cells spread or metastasize)
changes in composition of cell membrane or secreted products – extracellular matrix can influence whether neighbouring cells migrate

Question 37

What is a fate map

Answer 37

map of developmental fate of zygote or early embryo showing the adult organs that will devleop
-based on position on zygote (combined parent cells) or early embryo

Question 38

How is a fate map constructed

Answer 38

inject / mark up parts of the zygote then wait for it to develop and see where the mark is and do this with a bunch to see what each cell will do in embryo

OR by direct observation: done when the cells of early blastomeres have clear differences in pigment, so can remove cell and see what happens ie for sea squirt, muscle forming cells are yelloe always

can use vital dye: stain that doe not kill living cells, fluroescent better though can track it with photoactivated laser

transplant tissue to other embryo to see what it does

Chimeric embryos: embryos composed of cells from two or more different genetic sources ie quail cell in chick (quail nucleolus of cells was distinctive to help them mark things)

Transgenic chimeric embryos: transplant cells from genetically modified org carrying transgene that expresses flurescent protein into something that it non-transgeneic

Question 39

What is the function of the nucleolus

Answer 39

Ribosome biogenesis(RIBOSOME PRODUCTION FACTORY)
-making ribsomes (produces and assembles ribosomal subunits), done from translating mRNA

Nucleolus: most prominent structure in nucleus
-site of rRNA transcription and processing
-mammalian cell has 5-10 million ribsomes that are synthesized each time cell divides

Question 40

Homologous structures vs analogous

Answer 40

Homologous: derived from common ancestral structure
-dont necessarily perform same function ie our arms and bat wings

Analogous: perform same function but ndo not necessarily share common ancestral form (butterfly wings and bat wings, both fly but dont share ancestral form

Question 41

What are bird and bat wings

Answer 41

Both homologus and analogous

homologus bc as forelimbs, they shared a common ancestor with typical forearm structure

analogous: bc they both developed these wings for flying independently of eachother, they both dont have a shared common ancestor that was winged

Question 42

What is malformation vs disruption

Answer 42

Malformation
when the underlying cause of an abdormality is GENETIC (associated with gene mutation or aneuploidy)
-often associated with phenotypic syndrome

Disruption:
when underlying cause of abnormality is NOT GENETIC but caused from exogenous factors (such as chemicals, virsus, drugs)
-specific agents causing disruptions is called TERATOGEN

Developmental abnormalities are characterized as “malformations” if they are of a genetic nature or “disruptions” if they are associated with exposure to an exogenous agent such as a teratogen.

Question 43

What is a teratogen

Answer 43

-agent causing a disruption
-any agent that can disturb the proper development of embryo or fetus
-can result in birth defects or spontanous abortions

ex: drug thalidomide: prescribed to women for treating morning sickness, ended up being a severe teratogen that caused phocomelia (long bones of body absent, no arms or legs)

Question 44

is syndactly a malformation or disruption

Answer 44

malformation but for things like kangaroos, all ofthem have it so now it is apart of normal development