Chapter 8 Self-test questions

. Which of the following cells would be considered as differentiated?

Blastomere

Myoblast

Nerve cell

Stem cell

. Differentiated cells express the genes and proteins characteristic of their final identity in the adult, and that identity can be altered only under special circumstances. How does the concept of differentiation, as described here, differ from the concept of determination?

Determined cells have begun to differentiate, but are not fully differentiated.

Determined cells will continue to follow their fate if grafted into a different place in a host embryo, even though they do not yet express the genes and proteins characteristic of their final fate.

Determined cells are embryonic cells that will form certain cell types and structures if development is allowed to proceed normally, but will alter their development in response to their location if transplanted to a different place in a host embryo.

Determination describes fully differentiated cells whose identity can no longer be altered.

. Imagine that in an attempt to get the β-globin gene to be expressed in muscle cells, the transcription factors (GATA-1 and GATA-2) known to control β-globin gene expression in erythrocytes were introduced into muscle cells, yet the β-globin gene was not expressed. What is a likely explanation for this result?

The β-globin gene in the muscle cells is packaged into heterochromatin, and the erythrocyte transcription factors are insufficient to remodel that chromatin into an active state.

Erythrocyte transcription factors cannot interact with their target DNA sequences in muscle cells, even though those sequences are present and accessible.

Even though the necessary erythrocyte-specific transcription factors are now present in the muscle cells, the general transcription factors required for β-globin gene expression would not be present.

The cis-regulatory regions for the β-globin gene are present only in erythrocytes, and not in muscle cells, so the erythrocyte transcription factors would be meaningless in a muscle cell.

. The introduction of myoD into fibroblasts will cause

apoptosis

commitment to the myeloid lineage

differentiation into muscle cells

formation of red blood cells

. Differentiation, as opposed to determination, of muscle cells is dependent on

Mrf4

Myf5

MyoD

myogenin

. The many different cell types in the blood of an adult mammal are derived from

a single type of multipotent stem cell found in the bone marrow

differentiated cells that first developed in the fetal liver, but now reside in the bone marrow

division of differentiated cell types while circulating in the blood

stem cells that became committed to each specific blood cell type during embryonic development

. What is the developmental pathway by which the hematopoietic stem cell gives rise to a macrophage?

the hematopoietic stem cell divides, giving rise to a daughter cell that remains a stem cell and a daughter cell that differentiates directly into a macrophage.

the hematopoietic stem cell can give rise to either a lymphoid progenitor or a myeloid progenitor; the myeloid progenitor differentiates directly into a macrophage.

The hematopoietic stem cell can follow two paths, one called lymphoid and the other called myeloid, either of which can ultimately give rise to macrophages and other cell types such as osteoclasts and T cells.

the hematopoietic stem cell must first generate a cell of the myeloid lineage (as opposed to the lymphoid lineage), then a granulocyte/macrophage progenitor, then a monocyte, and finally a macrophage.

. What might be the result of producing a mouse knock-out for G-CSF?

The mouse would be unable to make granulocytes.

The mouse would be unable to make macrophages.

The mouse would lack red blood cells.

The mouse would lose its hematopoietic stem cell population completely

. Hematopoietic stem cells can be isolated and grown in culture; if one wished to control their differentiation into either neutrophils or macrophages, what colony stimulating factors could be used?

First, GM-CSF and IL-3 would be added to trigger formation of the granulocyte/macrophage lineage; then, the addition of either G-CSF or M-CSF would select between further differentiation as neutrophils or macrophages, respectively.

Since stem-cell factor (SCF) would maintain the cells as stem cells, the elimination of SCF would trigger differentiation into granulocyte/macrophage precursors; no further manipulation would be necessary.

The stem cells could be simultaneously stimulated with G-CSF, M-CSF, GM-CSF, and IL-3; half would become neutrophils and the other half would become macrophages; no further control is possible.

The addition of M-CSF alone to the medium would cause all the cells to become macrophages, whereas the addition of G-CSF would cause all the cells to become neutrophils; no other manipulation would be necessary, since this is the only difference between the two lineages.

. What is globin gene switching?

Globin gene switching refers to the switching from α-globin to β-globin, so that α₂β₂ hemoglobin can be made.

Globin gene switching refers to the molecular basis for the genetic disease sickle-cell anemia.

Globin gene switching refers to the transition, during fetal development, from the production of hemoglobin containing ε-globin, to γ-globin, to β-globin.

Globin switching refers to a genetic rearrangement in the DNA that joins different segments of DNA, resulting first in ε-globin synthesis, then γ-globin synthesis, and finally β-globin synthesis.

. What is the role of stem cells with regard to the function of adult tissues and organs?

Stem cells are undifferentiated cells that divide asymmetrically, giving rise to one daughter that remains a stem cell and one daughter that will differentiate to replace damaged and worn out cells in the adult tissue or organ.

Stem cells are embryonic cells that persist in the adult, and can give rise to all of the cell types in the body.

Stem cells are differentiated cells that have yet to express the genes and proteins characteristic of their differentiated state, and do so when needed for repair of tissues and organs.

Stem cells are fully differentiated cells that reside under the surface of epithelia, in position to take over the function of the tissue when the overlying cells become damaged or worn out.

. The stem cells responsible for renewal of the keratinocytes of the skin are found in which layer of the epidermis?

basal lamina

basal layer

dermis

keratinocyte layer

. Where are the stem cells that renew the epithelium of the gut found?

in the bone marrow

in the villi, underlying the dead outer layer of keratinocytes

near the bottom of the crypts

in the connective tissue underlying the gut epithelium

. What are satellite cells?

They are circulating cells 'orbiting' in the blood.

They are muscle stem cells.

They are muscle-associated support cells, much as glial cells are neuron--associated support cells.

They are neuronal stem cells.

. ES cells are

cells isolated from teratocarcinomas

embryonic stem cells derived from the inner cell mass of the mammalian embryo

epidermal stem cells found in the basal layer of the epidermis

human stem cells generated by treatment of mature cell types with a specific combination of transcription factors

. EpiSCs are

Epidermal stem cells derived from the embryonic epidermis

Stem cells derived from reprogramming which are different from embryonic stem cells

Embryonic stem cells derived from the embryonic epiblast

Epidermal cells committed for tissue repair

. What important lesson for the mechanisms of development can we derive from the ability to clone frogs by nuclear transfer?

that the selective gene expression seen in differentiated cells does not result from an irreversible loss of genes or their potential for expression

that the pattern of gene expression in a differentiated cell can only be reversed if the nucleus is removed from the cell

that the mechanisms of development are irreversible in all organisms except frogs

that a differentiated frog nucleus can be used to clone any species of animal, proving that development is directed by the egg, not by the nucleus

. If the lens of the eye is removed in the adult, which of the following organisms can produce a new lens by transdifferentiation of iris cells?

chicken

human

mouse

newt

. Which of the following cocktails of transcription factors, aka Yamanaka factors, can be used to generate iPS cells?

Oct4, Nanog, Smad and Cdx2

Gata4, Nanog, Gli and Cdx2

Oct4, Klf4, Sox2 and Myc

Oct4, Sox2, Gata4 and Rb

. What is the major concern in using retroviral vectors to deliver or activate pluripotency genes?

Not very efficient and needs repeated transfections

Plasmid diluted as iPS cells divide

Vector and transgenes remain in the genome and can be reactivated in differentiated cells

The vector integrates but is excised by the transposase

Chapter 8 Self-test questions

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