Development of multicellular organisms (Lecture 16) Flashcards
What is germ cell?
Germ cells give rise to gametes by differentiation and are found in gonads (testes and ovaries)
Germ cell vs primordial germ cell
PGC is found in early embryonic development while germ cell is found in gonads
What is the difference in gene expression in PGC vs somatic cells?
PGC express genes which maintain pluripotent and cell adhesion and migration
What is the migration path (3 places) of primordial germ cell?
- Epiblast 2. posterior end of the embryo 3. Gonads
Name 2 reasons of why PGC need to migrate?
- Protection of PGC in gastrulation (movement of ecto-meso-endoderms)
- To select the healthiest from those that can survive the migration
Is the migration path of primordial germ cells controlled by their environment using chemical signals?
Yes, in the experiment done with frogs, researchers placed the PGC in the blastula and place it elsewhere. Resultantly, the germ cells cannot reach their destination
Which phase of meiosis does replicated homologous chromosomes pair up and undergo recombination?
Prophase
How many cell divisions does meiosis have?
Two
How to ensure haploid gametes production in meiosis?
By replicating chromosomes before the first cell division, but not the second
What is polar body?
Small cell which is a product of meiosis during egg development, not involved in embryonic development
What are the 3 hypotheses which explain mammalian fetal ovarian gremlin death?
- Withdrawal of growth factors cause apoptosis to be triggered, as GF is needed to bind to receptors on the germ-cell surface
- Failure of meiotic recombination results in germ-cell death by defect
- The self-sacrifice theory: t the resources required to maintain the germline are limited, and that the germline cells therefore have a finite lifespan. By sacrificing the germline cells, the organism can conserve resources and allocate them towards the production of new, healthy germline cells, ensuring the continuation of the species.
What is fertilization?
Fusion of egg and sperm cell
Where does fertilization of mammals occur?
In the fallopian tube
Does the human sperm have centromere?
No it has centrosome for microtubules making
Suggest 1 role of polar body
In parthenogenesis of Komodo dragon, the mother’s half set of chromosomes doubles up. It is thought that the polar body acts as a sperm to turn eggs into embryos.
