BIO 2 Unit 1 study guide

Explain how Steward's carrot experiment and the nuclear transplantation experiment support one of the alternative hypotheses accounting for cell differentiation.

"If cells lose genetic material as they differentiate, then the nucleus of a mature, differentiated cell does not contain the "instructions" to develop other cell types?" Steward cut a slice of a carrot and placed the cells into a growth medium, which then developed into an entire carrot. this supports the differential expression of genetic material, no nuclear material is lost, the mature cell only expresses the material necessary to its specialized function. Steward supported the theory that all cells are totipotent. in Gurdon's nuclear transplantation experiment, he took the cells from an frog embryo placed in a growth medium, which then grew to be a tadpole. however, he also took cells from a tadpole and placed into a growth medium which grew into a ball of alike cells. which supports the theory that there is a progressive loss of genetic material, which also concludes that cells lose the ability to be totipotent.

Describe the two alternative hypotheses proposed to address how cells become more specialized in their structure and function during development.

Cell Differentiation through the progressive loss of genetic material: nuclear material is progressively lost until the cell contains only the material necessary for the function of the differentiated cell Cell Differentiation through the differential expression of genetic material: no nuclear material is lost. the mature cell only expresses the material necessary to its specialized function

Distinguish two alternative hypotheses that could account for how cells become differentiated during development.

Cells can differentiate through either: the progressive loss of genetic material>>>>> nuclear material is progressively lost until the cell contains only the material necessary for the function of the differentiated cell the differential expression of genetic material >>>>> no nuclear material is lost. the mature cell only expresses the material necessary to its specialized function

Be sure to know the goal/purpose, conclusion, and general methods for Spemann (1938)

Main conclusion>> cells with gray crescent cytoplasm cause development of the dorsal features

Be sure to know the goal/purpose, conclusion, and general methods for Spemann and Mangold (1924)

Spemann and Mangold (1924) concluded that the dorsal lip played a role in organizing the dorsal region of the embryo. It is known that the dorsal lip contains "gray crescent". Goal= explore the role of the dorsal lip of the blastopore as an organizer region Experiment= transplanted the dorsal lip cells of one gastrula to the ventral side of another gastrula Results= the transplanted dorsal lip induced nearby cells in the other gastrula to develop into dorsal features (notochord, neural tube) Conclusion= the dorsal lip functions as an organizer region, inducing changes in the surrounding tissue

What is the central dogma, and how does this relate to gene expression?

The central dogma describes gene expression (protein production) in all cells, but what controls which genes are transcribed and translated can be different for cells with the same nucleus the central dogma: DNA -> transcription - synthesis of RNA using a DNA Template mRNA -> translation - polypeptide synthesis directed by mRNA protein

Articulate why scientific literacy is important to society.

The reason why access to the literature is so important is because it is a reliable archive of scientific research. The fact that it is reliable does not mean that every published paper is correct, but it means that progress in our understanding can be tracked through time.

Define totipotent and pluripotent and relate them to cloning and the potential use of stem cells in medicine.

Totipotent: "all powerful" cells that have the potential to differentiate into an entire organism Pluripotent: cells that are capable of differentiating into several cell types cloning works because cells are totipotent the technique used in the nuclear transplantation study is also used in cloning stem cells are early development cells which are totipotent, thus have the ability to differentiate into any type of cell necessary Steps: 1. Differentiated body cell from an adult treated to "dedifferentiate". 2. Cell is fused with an enucleated unfertilized egg cell and implanted into a surrogate mother Totipotent cells may hold promise for regenerating lost/damaged tissue in adults (regenerative medicine) Embryonic stem cells (cells from early development embryos) may be totipotent,but there are ethical issues Adults also have stem cells in bone marrow (produce red blood cells) as of currently, there are artificial ears, bladders, and trachea

Describe how scientists use the words theory and hypothesis, and the relationship between experiments and hypotheses

a theory is a broad and well substantiated explanation or some aspect of the natural world that is consistent with available evidence ex: "All species are descended from a common ancestor" a hypothesis is a proposed explanation for an observed phenomenon that is based on knowledge and consistent with available evidence ex: "There are no polar bears in the Antarctic because there is no feasible route for them to get there from the Arctic." When conducting scientific experiments, researchers develop hypotheses to guide experimental design. A hypothesis is a suggested explanation that is both testable and falsifiable. You must be able to test your hypothesis, and it must be possible to prove your hypothesis true or false.

What is genomic equivalence? What is the difference between a totipotent and pluripotent cell, and where can you find these cells in humans?

genomic equivalence - all the different cell types in an organism have identical genomes (same DNA) because they all arose by mitotic cell division from the same zygote, But these cells express different genes Embryonic stem cells (cells from early development embryos) may be totipotent,but there are ethical issues Adults also have stem cells in bone marrow (produce red blood cells) but developmental potential is limited

How does the nuclear transplantation experiment relate to the process and issues associated with cloning?

in gurdon's nuclear transplantation, he took a un differentiated cell from a frog embryo and transplanted it into an enucleated egg cell which then grew to become a tadpole. he also took a cell from a fully differentiated cell and transplanted it into an enucleated egg cell, which then grew into a ball of identical cells because the cell had already differentiated into its final form, and could not dedifferentiate into any other cell type. in cloning, the mammary cells are taken from the donor and are forced to dedifferentiate by starving the cells, stopping the cell cycle. this allows the cells to be then transplanted into an enucleated egg and can then be developed into a full grown organism. however, through the process of dedifferentiation, the cell obtains more methyl groups than a young, undifferentiated cell, this means that the DNA is more tightly wound, and is hard to read for gene expression.

Describe the molecular processes guiding development, including cell signaling, gene regulation, and DNA replication.

molecular process: 1. gene regulation 2. DNA Replication 3. cell signalling and communication

What is the genetic code, and what are the 2 main properties of the genetic code we discussed?

the genetic code is expressed through codons. The code is: Redundant: multiple codons code for the same amino acid (but each codon has only ONE meaning). Universal: interpreted the same by all living organisms

What is cell differentiation?

the process by which cells become specialized in structure and function at a point, the cell becomes irreversibly committed to a particular cell type (determination)