lesson 20

what is the purpose of cell division?

1) cell division transforms a single-celled zygote into a multicellular organism. Without cell division, there would be no multicellular organisms consisting of hundreds, millions, or trillions of cells

development is comprised of what four major processes? which continue through adulthood?

1) cell division, cell differentiation, pattern formation, and morphogenesis. cell division and differentiation continue through adulthood

why do researchers use model organisms to study development?

1) they are less complex, easier to study, avoid ethical concerns, and draw parallels with humans and other animals.

what is the purpose of cell differentiation? How rapidly does differentiation occur?

1) to produce specialized (differentiated) cells

Compare and contrast reproductive cloning and therapeutic cloning in terms the steps involved and the potential use of each.

a. Both are cloning methods that remove the nucleus of a differentiated cell and insert it into an enucleated human oocyte. After that, the cell is allowed to developing into an embryo. However, while reproductive cloning implants the embryo into a surrogate mother, therapeutic cloning involves the embryonic stem cells that comprise the inner cell mass of the embryo being harvested and cultured in the lab. b. Reproductive cloning creates a genetically identical copy of an individual organism. It begins with the somatic cell nuclear transfer. This is where the nucleus from an adult mammary gland is inserted into an enucleated oocyte from a different animal. The resulting fused cell is allowed to develop into an embryo in the laboratory and is then implanted into a surrogate or foster mother. c. Therapeutic cloning does not result in a complete individual. Instead, it produces patient specific tissues that can be used in medical treatments. Tissues generated by therapeutic cloning could eliminate the risk of immune rejection that is inherent in organ transplants because the body will identify the transplanted tissues as belonging to itself.

compare and contrast somatic cell nuclear transfer (SCNT) and direct reprogramming in terms of the cells involved and the mechanisms by which nuclear reprogramming is achieved

a. SCNT is a method of of reprogramming in which he nucleus of a differentiated cell is removed from the cell and insert into an oocyte or zygote from which the original nucleus has already been removed in a process known as enucleation b. Direct reprogramming introduces expression of stem cell-associated transcription factors --> fibroblast --> induced pluripotent stem (iPS) cell c. Both of these methods reprogram the differentiated fibroblast nucleus back to a stem cell state but SCNT removes the nucleus of a differentiated cell and inserts it into an oocyte or zygote that's already had the original nucleus removed while direct reprogramming introduces transcription factors that are only expressed in stems cells into differentiated cells through a variety of different methods.

what is apoptosis and how does it differ from necrosis?

apoptosis is a highly controlled process of cell death that is activated by the expression of genes ina cell death pathway

what is an example of use of apoptosis during development?

apoptosis is activated by the expression of genes in a cell death pathway while necrosis is cell death caused by injury

what is cell cleavage, and how does it differ from later cell division events?

cell cleavage is when cell divisions occur to split the cytoplasm of the zygote into smaller volumes. the term cell cleavage comes about when this happens in an early embryo

epigenetic changes?

chemical modification of nucleotide bases and do not change the sequence of the cell's DNA but they do influence gene expression and are stable throughout cell divisions

what is the goal of pattern formation?

creates the body plant of an organism

how does nuclear reprogramming compare to differentation?

differentiation is the result of changes in gene expression and nuclear reprogramming an reset a differentiated cell to an undifferentiated cell

what type of cell forms the inner cell mass?

embryonic stem cells

true or false: nuclear programming requires genetic changes to the DNA

false

what processes does morphogenesis depend on?

it depends on cell growth, cell division, cell migration, changes in cell shape, and programmed cell death (apoptosis)

can only form certain cell types (ex: adult stem cells)

multipotent

what are hox genes and why are they important?

mutations that result in misidentification of embryonic segments

what is a possible consequence of hox gene mutation?

one notable effect of these genes is when they cause one segment of the embryo to develop as a different segment

what is the difference between pattern formation and morphogensis?

pattern formation creates the body plan of an organism while morphogenesis is the generation of an organism's body form

form all tissues of the organism. cannot form form extraembryonic tissues (ex: embryonic stem cells from blastocyst inner cell mass

pluripotent

what is the term for the cells generated by direct reprogramming and what concerns do they address?

pluripotent stem cells and they don't come from embryos

what are some examples of model organisms and the process(es) of development each is used to study?

roundworms (nematodes formally known as Caenorhabditis elegans (c. elegans for short)) are important to our understanding of development because it was the first model organism for which a complete cell lineage was mapped. the fruit fly (drosophila melanogaster) is used to study the mechanisms of pattern formation in embryos American clawed frogs (xenopus laevis) are also used as developmental models. Their large eggs - visible to the naked eye = make them ideal for studying the early cell divisions of the embryo

what are stem cells, and what is meant by "self renewal"?

stem cells are are any cells that have not adopted a particular cell fate and therefore have the potential to be come a one of a number of different types of cells

what complications are associated with SCNT-based approaches?

technical difficulties and ethical concerns

what is morphogenesis

the generation of an organism's body form

what are blastomeres?

the individual cells from the first few cleavages of embryo, which can be considered totipotent

what is development?

the process by which a single-celled fertilized egg (zyogte) becomes a fully formed adult.

form all tissues of an organism, plus the extraembryonic tissues (ex: zygote individual blastomeres from first few cleavages of the zygote)

totipotent

stem cells can be classified into one of four potency levels - be able to distinguish between the four levels and provide examples of cells at each potency level

totipotent, pluripotent, multipotent, unipotent

true or false: cells migrate through the extracellular matrix, a mixture of glycoproteins secreted by ccells to provide them with support and protectoin

true

can only form one type of cell (ex: spermatogonia (germ) stem cells)

unipotent

what is nuclear reprogramming

when a differentiated cell is reset to an undifferentiated stem cell state

what is a blastocyst?

when the embryo resembles a hollow ball