Defined as the process by which a fertilized ovum becomes a mature organism.
Development involves:
Division and growth of the fertilized egg into various cell types, tissues, and organs.
Arrangements dictated by the organism's genes, leading to species-specific body plans.
Totipotent cell: Capable of developing into any cell type.
Plasticity: Ability of a cell to change fate based on environment or gene expression.
Determination: Commitment of a cell to a specific fate.
Cloning: experiments on animals.
Key Transcription Factors in Muscle Differentiation:
MyoD, Myf-5, Myogenin, MRF4 determine muscle characteristics and differentiation.
Identification of Skeletal Muscle Fusion Factors:
Myomaker:
Involved in membrane hemifusion, enabling early fusion intermediate formation.
Myomerger:
Drives fusion pore formation and completes myoblast fusion.
Notably, their interaction is not required for function.
Plasticity Phenomena:
Differentiation into fast or slow muscle fibers, innervation patterns, exercise-induced adaptations, and nerve growth factors.
PNS:
Consists of the nerves and ganglia outside the brain and spinal cord.
Remarkable capacity to regenerate after injury, contrasting the CNS.
The PNS connects the CNS to body parts and serves as a relay mechanism.
CNS:
Consists of the brain and spinal cord
Integrates information and influences bodily activities.
Research indicates injury-induced reprogramming in PNS aids regeneration.
Dorsal Root Ganglia (DRG):
Bipolar neuron structure with unique regeneration rates post-injury (~1 mm/day for peripheral branch vs. limited central branch regeneration).
Plants: Cloning from isolated plant cells does not lose original genetic material during development.
Animals: Dolly the Sheep
Cloned in 1996 from a differentiated adult cell and significant as the first mammal cloned from an adult cell.
Pre-embryonic Stage (conception - 19d)
Key timings and developments (e.g. first cell division at 30h, zygote in uterine cavity at 4d, etc.).
Embryonic Stage (4w - 12 w)
Formation of the brain, heart, limbs, and sexual differentiation.
Fetal Stage (16w - 38w)
Rapid growth and maturation of organs, with the fetus becoming more recognizable as a human by the end of this period.
Ectoderm: skin, nervous system, and sensory organs, including the brain and spinal cord.
Mesoderm: muscles, bones, the circulatory system, and various internal organs such as the kidneys and gonads.
Endoderm: the lining of the digestive tract, respiratory system, and associated organs like the liver and pancreas.
Defines how ordered spatial arrangements of differentiated cells create tissues and organs.
Steps to pattern formation:
Definition of cells of a region.
Establishment of signaling centers that provide positional information.
Differentiation of cells within a region in response to additional cues.
Genes establish concentration gradients of morphogens that act as transcription factors that activate genes during cell development.
Egg-polarity genes:
determine body axes, with transcriptions from maternal origins influencing embryonic development.
Segmentation genes:
determines the number and orientation/polarity of the body segments.
Homeotic genes:
determine the identity of individual segments that have been established.
encode DNA-binding proteins
2 major clusters in Drosophila:
Antennapedia complex: head and anterior thoracic segments
Bithorax complex: posterior thoracic and abdominal segments
Hox genes:
Animals: a subset of homeotic genes that are crucial for establishing the anterior-posterior axis.
Expressed along the dorsal axis
Temporal Colinearity: 3’ expressed before the 5’
Spatial Colinearity: 3’ expressed anterior to the 5’
Positioning and expression of Hox genes reflecting limb and organ patterning
Lead to the formation of various body structures dealing with L/R symmetry.
Mutations in Hox genes lead to symmetry disorders.
Can cause randomization (situs ambiguus) or L/R reversal (situs inversus)
Often shown in conjoined twins
ZIC3 gene mutations are the most common known genetic cause of human laterality defects
Description of paracrine factors, their functions, and major families contributing to cellular signaling.
Fibroblast growth factor receptors (FGFR) are a family of receptor tyrosine kinases that are expressed in developing bone.
There are 4 FGFR genes
FGFR3 restrains chondrocyte proliferation and differentiation
FGFR3 mutations affecting bone growth and associated phenotypes.
Overactivation leads to skeletal defects with varying severities corresponding to mutation degrees.