20: Cellular Mechanisms of Animal Development Flashcards
Module 4, Lesson 3
The process by which a single-cell fertilized egg becomes a fully-formed adult is called…
Development
Development is regulated by…
Changes in gene expression over time
List the four major processes in development.
- Cell division
- Differentiation
- Pattern formation
- Morphogenesis
Which two developmental processes continue into adulthood?
Cell division and differentiation
Scientists often use ____ to study development.
Model organisms
List two benefits of using model organisms in developmental research.
- They are usually less complex
- They avoid ethical concerns surrounding manipulation of human embryos
C. elegans, a species of roundworm, is a model organism often used to study…
Cell division and differentiation
A ____ shows all cell divisions over an organism’s lifetime, describing the fate of each cell in the body.
Cell lineage map
Through studies on C. elegans, scientists learned about…
Cell division and how cells are assigned a particular fate
Fruit flies are a model organism used to study…
Pattern formation in embryos
Studies on fruit flies demonstrated that…
Development is driven by changes in gene expression
African clawed frogs are a model organism used to study…
Cell division and morphogenesis
Why were African clawed frogs ideal for studying morphogenesis?
They undergo a change from tadpole to adult
The most obvious developmental process is…
Cell division
During development, ____ transfroms a unicellular zygote into a multicellular organism.
Cell division
At what point in an organism’s lifetime does cell division occur the fastest?
Early embryonic stage
How is the early embryonic cell cycle different from the regular cell cycle?
(three)
- Only inclues S and M phases
- No cell growth occurs between divisions
- No G1 or G2 phases
The purpose of early embryonic cell division is to…
Split the zygote’s cytoplasm into smaller volumes
The early embryonic cell cycle is also called…
“Cell cleavage”
How does the later embryonic cell cycle differ from the early embryonic cell cycle?
(three)
- The cell cycle becomes longer
- Cell growth occurs
- Includes G1 and G2 phases
The production of specialized cells is called…
Differentiation
Differentiated cells arise from the division of undifferentiated…
Stem cells
Any cell which has not adopted a particular cell fate is a…
Stem cell
What happens to the daughter cells produced by stem cells when they divide?
- One cell gives rise to differentiated cells
- One cell replaces the original stem cell
The process by which the original stem cell is replaced by one of its daughter cells is called…
Self-renewal
Over time, differentiation causes gene expression to be…
Gradually altered
True or false:
Over time, the number of fates that a cell descended from a stem cell can adopt is restricted.
True
Differentiation occurs over ____ cell division(s).
Multiple
Stem cells are categorized by their…
Potency
A stem cell’s ____ represents the range of possible cell fates that the descendant cells may have.
Potency
List the four levels of stem cell potency.
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
A(n) ____ stem cell can form all tissues in an organism, including those needed for embryonic development.
Totipotent
True or false:
A single totipotent stem cell can develop into a complete organism.
True
List two examples of totipotent stem cells.
- The zygote
- Blastomeres
____ are cells that result from the first few divisions of the zygote.
Blastomeres
A(n) ____ stem cell can form all tissues in an organism except those needed for embryonic development.
Pluripotent
True or false:
A single pluripotent stem cell can develop into a complete organism.
False
It has the potential to do so, but cannot form the tissues needed to support an embryo
Embryonic stem cells are…
Pluripotent
Embryonic stem cells can be harvested from the…
Blastocyst inner cell mass
Why is the use of embryonic stem cells controversial?
Harvesting them requires destuction of the embryo
A(n) ____ stem cell can only differentiate into a few cell types.
Multipotent
Adult stem cells are…
Multipotent
In an adult organism, multipotent stem cells are responsible for…
Replacing old or worn-out tissues
A(n) ____ stem cell can only differentiate into one type of cell.
Unipotent
Germ stem cells, such as spermatogonia, are….
Unipotent
____ creates the body plan of an organism.
Pattern formation
During pattern formation, the genes a cell expresses depend on its…
Location within the embryo
The discrete sections of expressed genes established in pattern formation ultimately become…
Different body parts
List the three main body axes established by pattern formation.
- Anterior/posterior (head and hind)
- Dorsal/ventral (front and back)
- Left/right
____ genes are critical for pattern formation.
Homeobox
(Hox)
The expression of Hox genes causes…
Each body part to form in the correct spot
Each segment established in pattern formation gives itself a unique identity by…
Expressing different Hox genes
True or false:
Hox genes are highly conserved.
True
Mutations in Hox genes result in…
Misidentification of embryonic segments
An organism with a Hox gene mutation will have…
A fully-formed body part that is located in the wrong spot
Hox gene mutations and duplications are a major mechanism of…
Evolution
____ is the generation of an organism’s body form.
Morphogenesis
List the five processes that morphogenesis depends on.
- Cell growth
- Cell division
- Cell migration
- Changes in cell shape
- Programmed cell death
____ is programmed cell death.
Apoptosis
In order for the body to develop properly, some cells must be able to…
Migrate to different locations
Cells migrate through the…
Extracellular matrix
(ECM)
In order to migrate, cells must be able to change…
How they interact with the ECM
Many cells migrate by altering the expression of ____ on the surface of the plasma membrane.
Adhesion proteins
Cell ____ and ____ are associated with cell function.
Shape and structure
In order for a cell to function properly, it usually has to…
Change its shape
What happens if a cell cannot adopt the correct shape?
It cannot perform its function
____ is a highly controlled process of cell death activated by the expression of genes in a “cell death pathway”.
Apoptosis
____ is cell death due to injury.
Necrosis
When a necrotic cell dies, it…
Bursts and releases its contents into the ECM
When apoptotic cells die, they…
Gradually fragment into apoptotic bodies, which are then ingested and recycled by other cells
During early development, apoptosis is often used to…
Sculpt appendages
____ reverses cell differentiation by resetting a differentiated cell to an undifferentiated state.
Nuclear reprogramming
In order for nuclear reprogramming to occur, the ____ present in differentiated cell DNA must be reversed.
Epigenetic changes
List two methods of nuclear reprogramming.
- Somatic cell nuclear transfer (SCNT)
- Direct reprogramming
____ reverses cell differentiation by implanting a differentiated nucleus into an oocyte or zygote.
Somatic cell nuclear transfer
List the four major steps in SCNT.
- The nucleus is removed from an egg cell (oocyte) or zygote
- The nucleus is removed from a differentiated cell
- The differentiated nucleus is implanted into the oocyte or zygote
- Transcription factors in the oocyte or zygote reprogram the nucleus back to an embryonic stem cell state
True or false:
SCNT is capable of producing viable embryos.
True
The process of removing a cell’s nucleus is called…
Enucleation
____ reverses differentiation by introducing certain transcription factors into differentiated cells.
Direct reprogramming
The transcription factors used in direct reprogramming are…
Only active in stem cells
Direct reprogramming produces a(n)…
Induced pluripotent stem cell
(iPS cell)
True or false:
Direct reprogramming can be used to create viable embryos.
False
It produces pluripotent stem cells, which cannot develop into an embryo by themselves.
____ is a form of nuclear reprogramming that can be used to generate genetically identical organisms.
Reproductive cloning
True or false:
Reproductive/therapeutic cloning are quite similar to molecular cloning.
False
Reproductive cloning uses ____ to produce an embryo, which is then implanted into a foster mother.
SCNT
The offspring of reproductive cloning is genetically identical to the individual who…
Donated the implanted nucleus
____ is a form of nuclear reprogramming used to generate genetically identical tissues.
Therapeutic cloning
Therapeutic cloning uses SCNT to produce an embryo, then…
The embryonic stem cells are harvested and cultured
The embryonic stem cells extracted during therapeutic cloning eventually develop into…
Healthy tissue
List two potential applications of reproductive cloning.
- Reintroduction of extinct species
- Replication of important lines of livestock
List two potential applications of therapeutic cloning.
- Provide rejection-free organs and tissues
- Treatment of autoimmune diseases
List three reasons why nuclear reprogramming techniques are not commonly used.
- Technical difficulties
- Low success rate
- Ethical concerns
Why is considerable focus now being placed on iPS cells instead of nuclear reprogramming techniques?
They are not derived from embryos, thus alleviating ethical concerns related to using human embryos
