L2 - Germ Cells

Question 1

What is seen during development in terms of potency and specialisation

Answer 1

See a gradual restriction in potency of multipotent cells to specialised comitted cell fates

Question 2

Cells initially are

Answer 2

Totipotent

Question 3

Define pluripotent

Answer 3

Able to form all of the tissues of the body except the placenta `

Question 4

Describe what happens in the first 3 weeks post fertilisation

Answer 4

Body axes are gradually established

Question 5

What type of cells are set aside for the next generation

Answer 5

Gonadal germ cells

Question 6

In many animals there is an early division between __________ and ________ cells

Answer 6

Somatic and germ

Question 7

What is interesting RE somatic cells in plants

Answer 7

Are able to form new organims

Question 8

Where are the primordial germ cells determined

Answer 8

In a specific location on the edge or outside of the developing embryo

Question 9

PGCS

Answer 9

Primordial germ cells

Question 10

Where do PGCs migrate to

What do they become here

Answer 10

Migrate to the gonad

Become the progenitor population for eggs and sperm

Question 11

What do you need (2) for the determination of the germ cells

Answer 11

Totipotent (plastic) cells

Cell which is capable of underogoing meiosis

Question 12

Describe how the nematode worm gave us conceptual understanding about the formation of germ cells

Answer 12

Nematode worm has a specfic no cells (lineage can be traced)

Early assymetric divsions leads to the formation of the P lineage

This cell makes its way to the posterior of the cell

Question 13

Describe how asymmetric cell division takes place

Answer 13

Coupling the polarisation of the cytoplasmic determinants to the oriented plane of cell division

Question 14

What does the P cells act as

Answer 14

Pre germ cell

Question 15

Throughout asymm divisions what to the P cells inherit

Describe their composition

Answer 15

P-granules

Mix of protein and RNAs

Question 16

Describe how the P-granuel work

Answer 16

Binds to the DNA of the P cell and block alsmost all transcription and differentiation

Block translation in the cytoplasm

Promote stem cell fate and stimulate meiosis

Question 17

Describe what is seen when Nem worm P cells are stained for transcriptional

Answer 17

There is no transcriptional act

Question 18

Similar P-cell exist in vertebrates

Where are they found

Answer 18

Always at the posterior

Question 19

Germ line established which shows:

Answer 19

Little transcription and translation –> no differentiation

Able to undergo meiosis

Question 20

What mechanisms are involved in the shutting down of PGCs

Answer 20

Epigenetic silencing

Histone modifications (methylation and deacetylation)
DNA methylation

Question 21

PGCS arised from __________________

Answer 21

Extra-embryonic mesodendodermal cells

Question 22

Where do PGCS stay during axes formation

What is the reaosning behind this

Answer 22

Beyond the posterior part of the embryo

Protected form signals which are specifying the body axes

Question 23

Why are PGCs pluripotent

Answer 23

Because genes that code for differentiation factors are repressed transcriptionally and translationally

Question 24

When to PGCs migrate

Answer 24

Once rapid differentiation of embryogenesis begins to decrease

Question 25

Describe the migration of the germ cells

Answer 25

Passively ride the endoderm - attaches to endoderm to migrate through the midgut then attaches to the mesoderm

Question 26

Where is the final destination of the PGCs

Answer 26

Gonadal niche

Question 27

In the ovaries cells attach to the

Answer 27

Stromal caps

Question 28

In the testes the cells attache to

Answer 28

Hub cells

Question 29

Describe the migration of the PGCs in chick/mouse/human

Answer 29

Migrate throguh the posterior (hindgut) along a fibronectin rich trail Then leave the gut to move more laterally to the genital ridges

Question 30

What is the function of the gonadal niche

Answer 30

Provision of a specialist microenvironment which protects the PGCS in their pluripotent state

Question 31

Descrive the travelling stem cell niche idea

Answer 31

Support cells travel with PGCs secreting SCF to maintain the undiffernetiated cell type

Question 32

What is SCF

Answer 32

Stem cell factor

Question 33

What is the affect of a mutation which means SCF is unable to be produced

Answer 33

Stem cells are no longer protected and would differnetiate

Question 34

What is the affect of a mutation which means that the chemoattractant is no longer produced

Answer 34

Would get stuck in the gut and would fail to make it to the niche

Question 35

Describe how PGCS can lead to formation of teratomas

Answer 35

Failure to migrate to the protective niche would lead to the formation of teratomas

Question 36

What structure do cells at the periphery of the mammalian blastocyst form and from what fate is this

Answer 36

Cells on the outer periphery of a human/mammal embryo assume a different fate; the trophectoderm that forms the placenta

Question 37

What is the name given to the cells that occupy the inside of the trophoblast

Answer 37

Inner cell mass

Question 38

What is the significance of the cells inside the trophoblast not occupying the full space

Answer 38

The cells of the inner cell mass cluster at one side, the cells closest to the trophectoderm will give rise to the epiblast whereas the cells furthest from the trophectoderm will give rise to the hypoblast

Question 39

From which region of the human embryo are human ES cells found

Answer 39

Inner cell mass

Question 40

Define a stem cell

Answer 40

A cell capable of endless self-renewal and can give rise to a daughter that can give rise to several lineages

Question 41

How is a progenitor cell different to a stem cell

Answer 41

A progenitor cell is only capable of limited self-renewal as well as limited differentiation propensities

Question 42

What are the names given to the stem cells found in the mature tissues

Answer 42

Adult stem cells or tissue specific stem cells

Question 43

As development proceeds, most somatic cells become differentiated and not mitotic, T or F

Answer 43

T

Question 44

Describe the potency of adult stem cells

Answer 44

Multipotent or pluripotent

Question 45

What is meant by cellular homeostasis

Answer 45

Cellular homeostasis is the constant or periodic generation of new cells to replace old, damaged, and dying cells, or the addition of new cells as needed.

Question 46

Give an example of where cellular homeostasis changes during life

Answer 46

Pregnant females produce more red blood cells. RBCs are made continuously through life from haematopoietic stem cells in the bone marrow. Haematopoietic stem cells respond to increased levels of oestrogen found in pregnant females, to become hyper-activated and make many more daughter cells

Question 47

Adult regeneration/repair that occurs routinely in these tissues occurs via a very different mechanism to how they were first generated in the embryo, T or F

Answer 47

F - adult tissue regeneration/repair mirrors the way the cells form in the embryo

Question 48

What is meant by the niche in which tissue specific stem cells reside

Answer 48

complex microenvironments around the stem cells, made up of many cells, that interact with the environment and the stem cell to decide whether to activate it

Question 49

Haematopoietic stem cells give rise to all the blood cell types, what two classes of blood cells are these

Answer 49

Myeloid cells – monocytes, macrophages, neutrophils, basophils, eosinophils and erythrocytes as well as megakaryocytes/platelets and dendritic cells. Lymphoid cells – T, B and NK Cells

Question 50

Other than in the bone marrow, where else are HSCs found

Answer 50

Umbilical cord and placental tissue

Question 51

Stem cells respond to physiological signals, T or F

Answer 51

T

Question 52

What can the factors released by the adjacent cells of the HSC niche act to achieve

Answer 52

Regulate stem cell activity and the decision as to whether to remain quiescent, or become active. They can also trigger division to give another HSC or a daughter that will differentiate

Question 53

In which three regions are neural stem cells found

Answer 53

Subventricular zone lining the lateral ventricles, the subgranular zone and in the hypothalamus lining the 3rd ventricle

Question 54

What is the other name of neural stem cells

Answer 54

Neural precursor cells