Lecture 11&12- Animal Development & Ageing Flashcards
What is the fertilized egg called?
Zygote, one celled, formed right after fertilization?
What initially happens after fertilization? *photo
Zygote divides uniformly (2,4,8,16…), where it then forms a Morula (solid ball of cells)
What is a blastula?
It is a stage in cellular development where a blastocoel (fluid filled cavity) is present, as a result of cells growing away from a center (still no differentiated cells)
What happens during early gastrula?
- Blastula starts differentiating into ectodermal tissues and endodermal tissue
- archenteron forms as a result of the endoderm evaginating the blastocoel, forming a small cavity on the outside called a blastopore
- Organism is now 2 layered
What characterizes the late gastrula stage?
- Formation of the mesoderm via help from the endoderm and ectoderm
- closing off the blastopore
What are the endoderm, mesoderm and ectoderm referred to as?
Embryonic germ layers
What is another name for archentron?
Primitive gut- it is the endoderm
What does the Ectoderm form?
- Nervous system
- skin epidermis, and derivatives of them (hair,nails,glands)
- tooth enamel, dentin, and pulp
- epithelial lining of the oral cavity and rectum
What does the Mesoderm form?
- Musculoskeletal system
- skin dermis
- cardiovascular system
- urinary system
- lymphatic system
- reproductuve system
- most epithelial linings
- outer layers of respiratory and digestive systems
What does the endoderm form?
- epithelial lining of the digestive tract and respiratory tract (and their glands)
- epithelial lining of urinary bladder, thyroid and parathyroid glands
What is the Morula?
Stage in cell development where the organism is a solid mass of cells, after zygote
Describe the process of development of the nervous system in chordates
- Nervous system develops from the midline ectoderm by thickening of cells to form the neural plate
- two neural ends fold on either side of the neural plate to create a neural groove that eventually fuses into the neural tube
- Anterior (nearer to front ) end of the neural tube develops into the brain, rest is the spinal cord
What are the three interconnected developmental processes?
- Growth- through Mitosis
- Differentiation- in structure and function
- Morphogenesis- cell movement and pattern formation to -produce shape of organism’s body
Give 2 examples of model organisms used to research developmental genetics?
roundworm- C, elegans
Fruitfly- Drosphilia melanogaster
What are Maternal Determinants?
- They are mRNA or protein molecules initially present in the egg cytoplasm, stimulate early processes of development
- Segregation of MDs determine the types of cells and organs developing from the three germ layers; also help form the body axis
- Are unequally distributed during mitosis
- eventually run out
How do cells differentiate after MD’s are used up?
- Inducing development by signals called inducers(proteins), that are released by neighboring cells (eg Differenciated cell sends signal to undifferentiated cell to differentiate)
- inducers activate expression of particular genes
- ∴ induction requires transcriptional regulation of genes in a precise sequence
How is induction brought about in C. elegans for vulva formation?
- anchor cell induces vulva formstion
- cells closest to anchor cell receive the most inducers and develop into inner vulva
- inner vulva cells produce other inducers, neighboring cells differentiate to outer vulva
What is pattern formation?
The process that enables mrophogenesis
ensures proper strategic cell movement and organization so morphogenesis takes place
How is pattern formation regulated?
by the transcription of various gene sets
Give an example as to why apoptosis is important?
the formation of webbed hands/feet
What are egg polarity genes?
- they are genes that establish antereoposterior polarity (head/back side)
- they are present before egg fertilization
- they express MD’s in the form of mRNA that will be translated into proteins upon fertilization and will form gradients (morphogenes
What is the function of morphogenes?
Activate the expression of segmentation genes
What are zap genes?
- they are zygotes genes that are activated by the anterioposterior morphogene gradients
- divide the anterioprosterior axis into broad regions
- activate pair-rule genes
What are pair-rule genes?
- Genes that are expressed in alternating stripes
- body segments are formed along the antereoposterior axis
- Their protein products activate or suppress the expression of segment-polarity genes
What are segment polarity genes?
- genes that ensure that each segment has boundaries
- expressed in striped fashion
- twice as many stripes as pair-rule genes
What are homeotic genes?
- highly conserved genes (selector genes)
- found in many genomes including mice and humans
- code for Transcriptor factors (tf’s) that regulate which genes should be switched on/off
- homeotic tf’s dictate which body parts arise from which body segment
- mutations result in development of body parts in inappropriate areas
