Ch 16/17 quiz Flashcards
What leads to different cell types in an organism?
Differential gene expression
What is responsible for the transformation of a zygote into an organism?
Cell division, cell differentiation and morphogenesis
What is morphogenesis?
The physical processes that give an organism its shape, the development of the form of an organism and its structures
What are cytoplasmic determinants?
Unevenly distributed substances in the egg that influence early development such as mRNA, proteins and organelles
Why is uneven distribution if cytoplasmic determinants important?
After fertilization, divisions distribute the zygotes unevenly distributed cytoplasm to different cells, exposing different nuclei to different determinants. These determinants regulate gene expression
What is induction?
Signals/growth factors secreted by neighboring cells that cause changes in target cells
What are the major sources of developmental information?
- The egg’s cytoplasm-uneven distribution of determinants
2. The environment around a cell-this becomes more important as number of embryonic cells increase, induction
What is determination?
The term coined by biologists that means the unseen events that lead to observable differentiation of a cell. This is irreversible
What gives a cell its characteristic structure and function?
Tissue specific proteins-found only in specific cell types
What is the most important factor in maintaining gene expression?
transcription
What are examples of differentiated cells?
- Liver cells specialize in making albumin
- lens cells specialize in making crystallin
- Skeletal muscles have high concentrations of muscle-specific versions of contractile proteins myosin and actin
What are myoblasts?
muscles cells that appear to be the same as embryonic cells but have undergone determination. The churn out large amounts of muscle-specific proteins and fuse to form skeletal muscle cells
What is myoD?
A master regulatory gene that encodes the protein MyoD, a transcription factor that binds to specific control elements in the enhancers of various target genes and stimulates their expression. MyoD also also stimulates expression of myoD, helping to maintain a differentiated state. MyoD coordinately controls cells
How does commitment occur in cell differentiation?
Master regulatory genes and secondary transcription factors activate genes
What is apoptosis?
Programmed cell death. Occurs in cells that are infected, damaged or at the end of their lifespan. Cellular agents chop up DNA and fragment the organelles and the cells parts are packaged into vesicles. This protects surrounding cells from being damaged
What is blebbing?
A cell becoming multilobed as a part of apoptosis
Hiw is apoptosis triggered?
Signal transduction pathways activate a cascade of apoptotic proteins and enzymes that perform apoptosis
Where is apoptosis believed to evolve from?
early eukaryotes
Why is apoptosis important?
It is essential for normal development of the nervous system and normal morphogenesis of hands/paws
What is pattern formation?
The process of cytoplasmic determinants and inductive signals contributing to the development of spatial organization
What is positional information?
Molecular cues that control pattern formation provided by cytoplasmic determinants and inductive signals that tell a cell its location relative to the body axes and neighboring cells and determine how the cell and its offspring will respond to future molecular signals
How early does an egg provide positional information?
before fertilization
What are homeotic genes?
Genes that control pattern formation in the late embryo, larva and adult
What are embryonic lethals?
mutations with phenotypes that cause death at the embryonic or larval stage
What are maternal effect genes?
A gene that, when mutant in the mother, results in a mutant phenotype in the offspring regardless of the offsprings own genotype
What are egg-polarity genes?
Genes that control the polarity/orientation of the egg, and consequently the drosophila
What is a bicoid?
A maternal effect gene essential for setting up the anterior end of a fly
What are morphogens?
Gradients of substances that establish and embryo’s axes and other features of its form, apart of he morphogen gradient hypothesis
What is genomic equivalence?
The concept that all cells have the same genes
What is organismal cloning?
an organism or organisms that develops from a single cell without meiosis or fertilization producing one or more organisms genetically identical to the “parent” that donated the single cell
What was the significan of F.C. Syeward’s experiment?
He found that single differentiated cells taken from the root of a carrot could grow into normal adult plants that were genetically identical to the parent
What does totipotent mean?
A cell that can “dedifferentiate” then give rise to all specialized cell types in an organism
How were Robert Brigg’s and Thomas King’s experiments important? What about John Gurdon?
They all performed nuclear transplantations from an embryonic cell of a frog to a nucleus lacking egg. Gurdon concluded that the egg often formed a tadpole and nuclear potential is restricted bu embryonic development and cell differentiation
Who is Dolly?
A lamb cloned from an adult sheep by nuclear transplantation from a differentiated cell. The necessary dedifferentiation of the donor nuclei was achieved by culturing mammary cells in a nutrient poor medium, they fused with enucleated sheep eggs, and they formed embryos that were implanted into surrogate mothers
Why does cloning have low efficiency and high abnormality rates?
The DNA of cloned embryos often have more methyl groups that than normal embryos, these groups interfere with gene expression patterns and normal development. These changes must be accurately overcome in cloning procedures
What is a stem cell?
A relatively unspecialized cell that can reproduce indefinitely and, under certain conditions, differentiate into specialized cells
How are adult stem cells and ES different?
Adult stem cells cant give rise to all cell types in an organism, but can still give rise to multiple types
What does it mean to be pluripotent?
Capable of differentiating into many different cell types
What are iPS cells?
Indiced pluripotent stem cells. Cells that were transformed using retroviruses from differentiated cells to (seemingly) ES cells
What are oncogenes?
Cancer causing genes
What are proto-oncongenes?
Normal, noncancerous versions of genes that code for proteins that stimulate normal cell growth and division
How does an oncogene arise?
A genetic change that leads to an increase in either the amount of the proto-oncogene’s product or in the intrinsic activity of each protein molecule
What are the categories of generic changes that convert proto-oncogenes into oncogenes?
movement of DNA within the genome(translocated near an active promoter), amplification of a proto-oncogene, and point mutations in a control element(promoter/enhancer) or in the proto-oncogene itself
What are tumor-supressor genes?
Genes that encode proteins that help prevent uncontrolled cell growth
In what ways do tumor suppressor gene proteins inhibit uncontrolled cell growth?
- Repair damaged DNA to minimize cancer causing mutations
- Control adhesions of cells to each other or the extracellular matrix for proper cell anchorage(this is often absent in cancer)
- Serve as components of cell-signaling pathways that inhibit the cell cycle
What types of genes are ras genes and p53 genes?
ras: proto-oncogene
p53: tumor-suppressor gene
What is a ras gene?
Encode Ras protein, a G protein that relays a signal from a growth factor receptor on the plasma membrane to a cascade if protein kinases, the end of the cascade stimulates the cell cycle
How can ras gene mutations lead to cancer?
It can encode a Ras protein that triggers the cascade in the absence of a growth factor, resulting in cell division
In what ways does the p53 gene help prevent cancer?
- Activates other genes that halt the cell cycle
- Turn on genes involved in DNA repair
- Activates apoptosis when DNA repair is irreparable
What change are typically involved at least in making a cell cancerous?
the appearance of at least one oncogene and the lose of several tumor-suppressor genes
What types of genes are BRCA 1 and 2?
Tumor suppressor genes that protect against breast cancer that repair damaged DNA
How are people predisposed to cancer?
By inheriting an oncogene or mutant allele of a tumor-supressor gene, putting them one step closer to cancer
How can viruses cause cancer?
They can interfere with gene regulation if they integrate their their genetic material into DNA of a cell. Viral integration can donate an oncogene, disrupt a tumor-suppressor gene or convert a proto-oncogene into an oncogene. They can also produce proteins that inactivate tumor-supressor genes
What does a virus consist of?
nucleic acid surrounded by a protein coat
What is a capsid?
The protein shell enclosing the viral genome, built from a large number of protein subunits called capsomeres
What are viral envelopes?
A membranous envelope surrounding the capsids derived from the membranes of the host cell containing phospholipids and membrane proteins along with glycoproteins
What is the host range?
The number of host species a virus can infect
What is the lytic cycle?(include steps)
A phage replicative cycle that ends in death of the host cell
Steps
- Attachment of phage to bacteria
- Entry if phage DNA/degradation of host DNA
- Synthesis of viral genome/proteins
- Assembly of new phages
- Release of new produce phages, breaking the cell wall and killing the cell
What is a virulent phage?
A phage that replicates only by a lytic cycle
What 3 things have helped bacteria from going extinct as a result of phages?
- Natural selection favors bacteria with receptors not favored by the phage
- Bacteria have restriction enzymes as defense
- Many phages coexist with bacteria instead of using the lytic cycle
What is the lysogenic cycle?
Allows replication of the phage genome without destroying the host
What are temperate phages?
Phages capable of using both modes of replicating
What is a prophage?
When a phage DNA molecule is incorporated into a specific site on the bacteria chromosome by viral proteins that break circular DNA and join them together
Describe the process of viral infection by viruses with viral envelopes
The glycoproteins protruding from the envelope bind to receptor sites ok the host cell. The capsid and genome enter the cell, then the capsid is digested which releases the viral genome. The viral genome undergoes transcription and serves as the template. Complementary RNA makes proteins in the cytosol and glycoproteins in the ER and golgi apparatus. Vesicle then transport envelope glycoproteins to the membrane and a capsid assembles around each genome molecule and leaves the cell
What are the 3 types of single-stranded RNA genomes found in animal viruses?
- Genome serves directly as mRNA and can be translated into viral protein immediately after infection
- RNA genome serves as a template for mRNA synthesis, the RNA genome is transcribed into complementary RNA strands which functions as mRNA and templates for more copies of RNA
- Retrovirus cycles
What are retroviruses?
Viruses equipped with reverse transcriptase, which transcripts an RNA template into DNA making an RNA to DNA flow, the opposite from the normal direction
What is HIV?
A retrovirus that causes AIDS
What is a provirus?
The newly made viral DNA that enters a cell’s nucleus and integrates into the DNA of the chromosome in a retrovirus cycle. This DNA remains there permanently. It gets transcripted into mRNA for new viruses to be produced
How are prophages and proviruses different?
A prophage leaves the host’s genome at the start of the lytic cycle
What are candidates for the original source of the viral genome and why?
- Plasmids: They are small, circular DNA molecules found in bacteria and yeast and ca replicate independently of the genome and are occasionally transferred between cells
- Transposons: DNA segments that can move from one location to another in a cell’s genome.
Plasmids, transposons and viruses are mobile genetic elements
How do most antiviral drugs work and what is an example?
Drug resembles a nucleotide and interferes with viral nucleic acid synthesis
- acyclovir, impedes herpesvirus by inhibiting the viral polymerase from synthesizing viral DNA
- AZT, curbs HIV replication by interfering with the synthesis of DNA by reverse transcriptase
What are the methods of treating viruses?
- Vaccines
- Antiviral drugs
- “cocktails” or multidrug treatments-commonly include a combination of 3 nucleosode mimics and a protease inhibitor that inhibits assembly enzymes
What is an epidemic and a pandemic?
Epidemic: a general outbreak
Pandemic: A global epidemic
What processes contribute to the emergence of viral diseases?
- Mutation if existing viruses, especially common in RNA replication errors
- dissemination of a viral disease from a small and isolated human population
- Spread of existing viruses from animals
What are the types of influenza and which one(s) have caused epidemics?
A, B, C. Type A has caused epidemics
How do viruses spread in plants?
- Horizontal transmission: Plant is infected from an external source
- Vertical: A plant inherits a viral infection from a parent
How do viral macromolecules pass between plant cells?
They use proteins that enlarge the plasmodesmata
