Gene Transcription
A researcher finds that a region of DNA is tightly associated with histone proteins and is transcriptionally inactive. The DNA appears as densely packed “beads” that prevent access to transcriptional machinery. This form of chromatin is called what?
What is heterochromatin?
A newly transcribed RNA molecule contains both introns and exons and is longer than the mature mRNA found in the cytoplasm. What is this initial RNA transcript called?
What is nuclear RNA (nRNA), or premessenger RNA?
During organ development, one tissue releases a signal that causes an adjacent tissue to change its developmental fate. The signaling tissue is referred to as the inducer, while the tissue responding to the signal is called what?
What is the responder?
A developing tissue is exposed to an inductive signal but fails to differentiate because it lacks the molecular machinery necessary to respond to that signal. What term describes the tissue's ability to respond to an inductive signal?
What is competence?
A developing cell receives a signal from SHH. Under normal conditions, Patched inhibits Smoothened, but SHH binding to Patched removes this inhibition. Smoothened then activates a pathway that ultimately increases transcriptional activity of this family of transcription factors.
What are the GLI transcription factors?
A mutation prevents RNA polymerase II from properly initiating transcription of a gene. The mutation occurs in a promoter sequence containing a repeated two nucleotide sequence. What is this promoter element called?
What is the TATA box?
A single human gene produces different proteins in kidney cells and gonadal cells because different combinations of exons are retained in the mature mRNA. What process accounts for this phenomenon?
What is alternative splicing?
During kidney development, the ureteric bud interacts with the surrounding metanephric mesenchyme to induce formation of nephrons. This developmental interaction is an example of what general type of tissue interaction?
What is an epithelial–mesenchymal interaction?
A developmental signaling molecule is secreted by one cell, diffuses a short distance through the extracellular environment, and binds to a receptor on a neighboring cell. What type of cell-to-cell communication is occurring?
What is paracrine signaling?
During neurulation, the neural plate becomes narrower and longer as cells change shape, move medially, and intercalate with neighboring cells. Disruption of the signaling pathway responsible for this process can produce neural tube defects. What developmental process is being described?
What is convergent extension?
A transcription factor binds to a regulatory DNA sequence located thousands of base pairs away from a gene's promoter. This interaction increases the rate of transcription by altering chromatin structure and facilitating RNA polymerase binding. What type of regulatory element is involved?
What is an enhancer?
A mutation disrupts a complex responsible for recognizing the 5′ and 3′ splice sites of a premessenger RNA. As a result, introns are not properly removed before the RNA reaches the cytoplasm. What cellular structure has been disrupted?
What is the spliceosome?
A ligand binds the extracellular domain of a membrane receptor, causing activation of its intracellular tyrosine kinase domain. The receptor then phosphorylates downstream proteins, ultimately activating a transcription factor that alters gene expression. What type of cellular process does this sequence represent?
What is a signal transduction pathway?
Cells within a developing limb are exposed to different concentrations of the same diffusible signaling molecule. Cells exposed to higher concentrations activate a different set of genes than cells exposed to lower concentrations, resulting in different developmental fates. What class of signaling molecule produces this concentration-dependent patterning?
What is a morphogen?
Mutations in several genes involved in a noncanonical WNT signaling pathway—including FZ, CELSR, VANGL, and DVL—can interfere with the cellular movements required during neural tube formation and have been associated with neural tube defects. What developmental signaling pathway is disrupted?
What is the planar cell polarity (PCP) pathway?
Two cells contain identical DNA sequences but express different sets of proteins. In one cell type, promoter regions of muscle-specific genes are largely unmethylated, while genes encoding blood-specific proteins are highly methylated. What mechanism best explains this tissue-specific pattern of gene expression?
What is DNA methylation–mediated epigenetic regulation?
Two cell types contain the same gene but produce proteins with different structures and functions. One mechanism involves generating different mature mRNAs by removing different introns and combining exons in different patterns. The resulting proteins are known by what term?
What are splicing isoforms (splice variants)?
A developing cell receives a signal from an adjacent cell through a membrane-bound ligand rather than a diffusible signaling molecule. The Notch pathway is a classic example of this type of communication. What is this signaling mechanism called?
What is juxtacrine signaling?
A developing chondrocyte must attach to extracellular matrix proteins in order to differentiate appropriately. Cell-surface receptors bind molecules such as fibronectin and laminin and connect them to the intracellular actin cytoskeleton. What are these receptors called?
What are integrins?
After SHH is synthesized, cholesterol is added to its C-terminus and palmitic acid is added to its N-terminus. Cholesterol is particularly important for anchoring SHH to the membrane, transporting it out of the cell, and establishing the concentration gradients required for its morphogen function. What molecule is essential for these SHH activities?
What is cholesterol?
A patient has a genetic disorder in which only the allele inherited from one parent is normally expressed, while the allele inherited from the other parent is transcriptionally silenced. This parent-specific gene expression results from epigenetic modification established during gametogenesis. What is this phenomenon called?
What is genomic imprinting?
A newly synthesized protein is present in a cell but remains inactive until it undergoes a specific chemical modification or proteolytic cleavage. These changes occur after translation and can alter the protein's activity, localization, or interactions. What general process accounts for these changes?
What are posttranslational modifications?
A mutation disrupts a receptor involved in a pathway that is particularly important for limb development, axon growth, angiogenesis, and mesoderm differentiation. The receptor belongs to a family of receptor tyrosine kinases. Which signaling family is most likely affected?
What is the fibroblast growth factor (FGF) family?
A mutation eliminates the function of one developmental signaling protein, yet the embryo develops relatively normally because another member of the same signaling family compensates for its loss. Additionally, interconnected signaling pathways provide alternative mechanisms for regulating the same developmental process. What principle of developmental signaling best explains this observation?
What is redundancy and crosstalk between signaling pathways?
A fetus has cardiac outflow tract abnormalities accompanied by skeletal, ocular, renal, and hepatic abnormalities. Genetic testing identifies a mutation affecting JAG1, a ligand involved in juxtacrine signaling. Dysfunction of which developmental signaling pathway best explains these findings?
What is the Notch signaling pathway?