quizzes

• Keratin is produced by some epithelial cells but not others
• Morphogenesis is one of the most important categories of questions addressed by developmental biologists
• Gastrulation involves the most substantial rearrangement of cells, giving rise to three embryonic tissue layers
• Germ cells arise from cells that separate before formation of the ectoderm, mesoderm, and endoderm
• Chimeric embryos are embryos produced by combining cells from different genetic sources
• If a cell from the dorsal surface of a gastrula is transplanted to the ventral surface and the embryo develops normal dorsal and ventral structures, the tissue removed for transplant has an undetermined fate at the time of transplant
• Levels of commitment in order: Undifferentiated, specified, determined, differentiated
• Autonomous specification does not require interactions with other cells, while conditional specification requires interactions with other cells
• A fate map is generated by researchers labeling embryonic cells to determine their locations in the adult organism
• A syncytium is a mass of cytoplasm with multiple nuclei
• An epigenetic effect example is a gene being inactivated by histone methylation
• If a transcript is produced without a polyA tail, it would be relatively unstable and degrade rapidly
• The region that includes the start codon AUG is the Kozak consensus sequence
• Insulin is maintained in an inactive state until needed by being produced in an inactive form that must be cleaved by an enzyme to produce the active form
• A genome is the entire set of genetic material of a particular organism
• Alternative pre-mRNA splicing describes the process by which pre-mRNA may be processed in multiple ways to produce mature RNA molecules that encode different proteins
• Tightly packed DNA (heterochromatin) is not expressed
• RNAi can bind to ssRNA, inhibiting expression of that RNA
• Transcription factors can have varied effects depending on the combination of transcription factors with which they interact
• mRNA stability is particularly dependent on the length of its 3'UTR, which is important in determining the length of the polyA tail
• Typical miRNAs have 22 nucleotides
• mRNA is translated in the cytoplasm
• Lin-4 is a microRNA found in C. elegans
• mRNA stability is most dependent on the length of its polyA tail
• Maternal contributions contribute to maintaining the normal rate and pattern of early cell divisions without DNA
• A major characteristic of receptor tyrosine kinases (RTKs) is that in response to binding of a paracrine factor, a series of events occur that result in phosphorylation of specific tyrosine residues by ATP
• If endodermal and mesodermal tissues of an embryo are separated early in development and recombined in the absence of ectoderm, the endodermal tissues will segregate outside of the mesodermal tissues
• One obstacle to the use of simple diffusion to transport morphogens is that morphogens are not always water-soluble
• If a chemical signal triggers a response in a nearby cell separated by extracellular matrix, paracrine signaling is occurring
• Caenorhabditis elegans (nematode roundworms) has been valuable in understanding interactions between paracrine and juxtacrine signaling during vulval induction
• The two paracrine factors secreted by the optic vesicle are BMP4 and Fgf8
• Activin was used in experiments to demonstrate that regulation by gradients of paracrine factor concentration is involved in the specification of different mesodermal cell types
• Every inductive interaction has at least two components: an inducer and a responder
• A permissive interaction is used to describe an interaction in which the responding tissue has already been specified