SAQ- 2021/2022

Question 1

List thekey components including the types of cells required to
generate an organoid model.

Answer 1

• Stem cells
• Tissue-specific cells
• extracellular matrix (ECM) - scaffold made of proteins
• Growth factors- signalling molecules
• Nutrient medium
• Bioreactor or culture system
• Cellular interactions
• Matrigel/Hydrogel

Question 2

How does the timescale of somitogenesis compare across
vertebrate species?

Answer 2

Varies widely; shorter in some vertebrates (e.g., zebrafish), longer in others (e.g., human).

Influenced by
* species size
* development speed
* specific embryonic requirements

Question 3

Describe the stepwise differentiation from a pluripotent stem cell to a
skeletal muscle cell.

Answer 3

1. Pluripotent Stem Cell: Begins as an undifferentiated cell with the potential to become any cell type.
2. Mesoderm Formation: Undergoes mesoderm induction, forming mesodermal cells that give rise to muscles.
3. Myogenic Specification: Receives signals to become a myoblast, a muscle precursor cell.
4. Myoblast Proliferation: Myoblasts divide and replicate to amplify their numbers.
5. Myoblast Fusion: Myoblasts fuse together to form a multinucleated myotube.
6. Myotube Maturation: Myotube matures, developing muscle-specific structures.
7. Myofiber Formation: Myotube further differentiates into a mature muscle fiber (myofiber).
8. Muscle Function: The myofiber gains contractile proteins and becomes capable of contraction, functioning as a skeletal muscle cell.

Question 4

What is the role of Stra8 in germ cell development and how is it
controlled?

Answer 4

Role in germ cell development
* Key regulator
* promotes transition of primordial germ cells (PGCs) from mitotic to meiotic state
* >gametogenesis
*&raquo_space;meiotic recombination and progression
*&raquo_space;genetic diversitu and forming haploid gametes

Control of Stra8
* expression controlled by retinoic acid
* activates Stra8 gene
* triggers switch from mitosis to meiosis in developing germ cell
* balance of RA signalling vital
* >inccorect timing can disrupt germ cell development
* Proper timing for meiosus and gametogenesis

Question 5

What is the function of the uterine decidua?

Answer 5

1. Implantation support: receptive environment for fertilized egg (blastocyst) to implant -> uterine wall
2. Nutrient Exchange: exchange of nutrients and waste products - maternal bloodstream and developing embryo
3. Hormone secretion: progesterone, human chorionic gonadotropin (hcG) > maintain pregnancy and supporting embryo growth
4. Immunological Protection: Modulate maternal immune response, prevents immune system rejecting developing embryo
5. Protection and nourishment: protective layer, nourishment early stages of pregnancy

Question 6

Sox9 is required for male development. Give three examples of how
it is induced in different vertebrate species.

Answer 6

*

Question 7

Describe the transplantation experiments that led to the discovery of
conditional specification in the amphibian embryo.

Question 8

List the key events in the “chase and run” model for chemotactic
neural crest cell migration.

Question 9

How is pluripotency maintained in the inner cell mass (ICM) in the
blastocyst?

Question 10

What are the mechanisms that form the Nieuwkoop centre in the
amphibian embryo?

Question 11

List the main epigenetic modifications occurring on chromatin.
Include whether they are likely to cause an increase or decrease in
transcription.

Question 12

1l. Describe, with the use of a diagram how DNA methylation changes
during pre-implantation embryo development. Include the relevant
enzymes that mediate the methylation changes.

Answer 12