DAT: Developmental Biology

reproduction producing genetically identical offspring (clones)

Asexual Reproduction

reproduction producing genetically different offspring.

Sexual reproduction

• Cortical reaction forming fertilization envelope via calcium release

• release of cortical granules is a form of exocytosis

Slow Block

Sodium ions diffuse into the egg and the egg depolarizes

Fast Block

Triggered in the oocyte after sperm entry, forming mature ovum and polar bodies.

Completion of Meiosis II

• Indeterminate cleavage

• single fertilized egg splits into two

Monozygotic Twins

two separate eggs are fertilized by two individual sperm

Dizygotic Twins

• Rapid mitotic divisions of the zygote without overall growth

• forming blastomeres.

Cleavage

division from pole to pole.

Polar cleavage

Cleavage that uniformly divides the whole embryo

Holoblastic cleavage

• partial cleavage

• embryos with a lot of yolks

• birds, reptiles, fish, monotremes, and mollusks

Meroblastic cleavage

division parallel to equator.

Equatorial cleavage

deuterostome cleavage with aligned cells

Radial cleavage

protostome cleavage with shifted cells

Spiral cleavage

• cells produced by cleavage with reduced cytoplasm

• cytoplasm mass of the _ is less than the mass of the zygote

• Each cell of the zygote during the cleavage phase is considered _

Blastomeres

Direction of cell division; spiral (protostomes) or radial (deuterostomes).

Axis of Cleavage

blastomeres can form entire embryo

Indeterminate Cleavage

• blastomeres already specialized

• isolated blastomeres will die or arrest

Determinate Cleavage

solid ball of ~8 totipotent cells

Morula

trophoblast (an outer ring/layer of cells) and the inner cell mass (embryonic disc)

Blastula

• implanted human blastula with inner cell mass

• composed of Trophoblast and inner cell mass

• To have the successful implantation of the _, zona hatching needs to occur

• fertilized embryo implants into the uterine wall at _ stage

Blastocyst

• cavity within blastula

• morula cells continue through cell division, a hollow liquid cavity forms

Blastocoel

able to form all tissues but not entire organism

Pluripotent

• entire organism possible

• cells that make up the morula

• ex) zygote & blastomeres

Totipotent

• limited tissue range

• ex) stem cell in the bone marrow

Multipotent

one cell type

Unipotent

• Formation of three germ layers: ectoderm, mesoderm, and endoderm

• Invagination of cells mark the start of _

Gastrulation

Opening that forms during gastrulation; becomes mouth (protostomes) or anus (deuterostomes).

Blastopore

• Primitive gut formed during gastrulation.

• precursor of the digestive tract or gut of the sea urchin

Archenteron

nervous system

Ectoderm

adrenal medulla

Ectoderm

neural crest derivatives

Ectoderm

sensory organs

Ectoderm

epidermis

Ectoderm

muscles

Mesoderm

bones

Mesoderm

circulation

Mesoderm

kidneys

Mesoderm

gonads

Mesoderm

dermis

Mesoderm

adrenal cortex

Mesoderm

digestive/respiratory lining

Endoderm

liver

Endoderm

pancreas

Endoderm

thyroid

Endoderm

bladder lining

Endoderm

Undifferentiated cells capable of differentiating into specific cell types based on potency.

Stem Cells

Notochord development → bending of the neural plate → formation of the neural tube

Neurulation steps

Mesodermal structure that signals ectodermal differentiation; forms basis of spinal column

Notochord

Migrate to form teeth, facial cartilage, and pigmentation cells.

Neural Crest Cells

CNS precursor

Neural tube

Mesodermal cells that form vertebrae and skeletal muscles.

Somites

terrestrially-adapted eggs

Amniotes

• outer membrane forming placenta in mammals

• In birds and reptiles, gas exchange is mostly managed by this

Chorion

• Sac for waste storage and gas exchange

• forms umbilical cord and bladder in mammals

Allantois

Provides early nutrients and first site of blood cell formation before placenta develops.

Yolk Sac

Process by which organizer cells influence development of nearby cells.

Embryonic Induction

Determine structure placement and body plan; include HOX genes for anterior-posterior axis

Homeotic Genes

Conserved DNA sequence in homeotic genes across species

Homeobox

uneven egg components influencing fate

Cytoplasmic determinants

inhibits FSH release from anterior pituitary.

Inhibin

upper pole with less yolk

Animal pole

lower pole often containing abundant yolk and forming extra-embryonic membranes.

Vegetal pole

• frog region opposite sperm entry marking future dorsal side

• Rotation of cytoplasm of the embryo after fertilization

Gray crescent

external fertilization

Ovuliparity

egg laid

Oviparity

egg retained but not nourished

Ovoviviparity

live birth nourished internally

Viviparity

• egg-laying mammals (platypus, echidna)

• Absence of nipples

Monotremes

sites of gas/nutrient exchange

Chorionic villi

maternal and fetal blood not directly connected

Placental blood flow

fertilization outside body

In vitro fertilization

sperm injected directly into egg (~75% success)

Microinjection IVF

natural fertilization.

In vivo conception

organ formation

First trimester

fetal movement and uterine growth

Second trimester

rapid growth (~1.6 ft and 7 lbs)

Third trimester

present in fertilization to prevent: Multiple sperms from penetrating one egg

polyspermy block

Capacitation → acrosomal reaction → polyspermy block

Fertilization

Cleavage → morula → blastula → gastrula

Zygote development

• produces hCG to maintain estrogen and progesterone production from the corpus luteum, which maintains the endometrium

• gives rise to Placenta and chorion

trophoblast cell

Chorion, allantois, amnion, yolk sac are all _

Extraembryonic membranes

• protection of developing embryo

• Fish do NOT have this

• shock absorption

Amnion

In frog embryos, gastrulation starts at _

Dorsal lip

used in fertilization for same species recognition

Zona pellucida

• Each cell of the zygote during the cleavage phase

• smaller than the zygote

• cytoplasm mass of the _ is less than the mass of the zygote

Blastomere

Cleavage → morula → blastula → gastrula

zygote development

Meroblastic cleavage, extraembryonic membranes, and a primitive streak

bird embryo

presence of Animal and vegetal pole

Polarity

uneven holoblastic cleavage

Frog

directly surrounded by Endoderm

archenteron

mesoderm-derived cartilaginous rod that induces spinal cord formation

Notochord

Lay eggs without amnion

Anamniotes

gives rise to Epiblast and hypoblast layers

inner cell mass

directly leads to the formation of Three germ layers

primitive streak