BOT 331 Exam 5 Questions With Correct Answers

Which mutant has a greatly increased number of stem cells in the shoot apical mersistem? A mutant that has NO functional WUS. A mutant that has NO functional PIN protein. A mutant that has NO functional CLAVATA3. A mutant that has NO functional WOX5. - Answer A mutant that has NO functional CLAVATA3. Choose a tropism. State how the environmental cue is perceived AND explain how perception causes growth to be redirected towards or away from the cue. - Answer Phototropism occurs when a plant receives stimulus (cue) from a light source and the plant grows towards or away from the light source. Photoreceptors (phototropins) absorb blue light which causes a signal pathway to bend towards the blue light. Cells elongate on the shaded side of the shoot and cause a bending towards the light source. How does a loss of GNOM function result in an equal distribution of auxin in an embryo? - Answer GNOM regulates the delivery of vesicles to the plasma membrane, but to one side of a cell. Vesicles delivering PIN proteins, therefore, results in PINs being delivered to one side of the cell. PINs transport auxin out of cells, and because of asymmetric distribution, transport auxin in one direction, which results in embryo positions that have greater amounts of auxin. If GNOM does NOT function, then PIN proteins have a symmetrical distribution, auxin is transported in all directions and the result is an equal distribution of auxin throughout the embryo. The first division of a plant zygote is said to be asymmetric. What makes the division asymmetric? - Answer After fertilization, the zygote elongates and many of the organelles are positioned to the apical end of the cell, while the vacuole is positioned to the basal end. When the zygote divides, the result are two different cells: a basal cell with a large vacuole and an apical cell dense with organelles. Because the two daughter cells are structurally distinct, the cell division is said to be asymmetric. A difference in tissue structures between the adaxial and abaxial sides of a leaf is called leaf polarity. phototropsim. genetic redundancy. a PHAN mutation. - Answer leaf polarity. A RNA that binds to and targets a messenger RNA for degradation is called an antisense strand. degradative RNA. a type of gene that codes for a small protein. microRNA. - Answer microRNA. True/false, if false explain why Polar transport of auxin requires that a plant cell have a symmetrical distribution of PIN proteins in the cell's plasma membrane. - Answer False, symmetric means PINs are distributed equally to all sides of the cell. PINs transport auxin. If symmetrically distributed then auxin would be transported in all directions, instead of one direction. Polar means one direction. For Polar transport, PINs must have an asymmetric distribution. True/false, if false explain why Cells in the peripheral zone of a shoot apical meristem divide to initiate a lateral shoot organ, such as a leaf. - Answer True. The peripheral and rib zones of the shoot apical meristem include the protoderm. ground meristem, and the procambium. Lateral organs, such as leaves, are initiated by cells in the shoot apical meristem. True/false, if false explain why A plant that shows vivipary must be synthesizing excess amounts of abscisic acid during seed maturation. - Answer False, high amounts of ABA favor seed dormancy, so prevent germination. Early germination as in vivipary (germinating while still on the mother plant) happens when ABA is NOT synthesized or cells cannot respond to ABA. True/false, if false explain why The gibberellin receptor is a repressor of a transcription regulator called DELLA-GRAS. - Answer False, DELLA-GRAS is a transcription regulator that prevents a set of genes, needed for GA response, from being expressed. DELLA is a repressor of the GA response. GID1 is the receptor for GA. When GID1 binds GA, then GID1 'tags' DELLA with ubiquitin, so DELLA the repressor is degraded and expression of genes needed for GA response can proceed. True/false, if false explain why MONOPTEROS is a transcription regulator that turns on the expression of α-amylase during seed germination. - Answer False, MONOPTEROS is NOT part of the gibberellin pathway. GA signals, after several steps, the expression of alpha-amylase, which gets secreted and breaksdown starch for sugar mobilization to the embryo. MONOPTEROS is part of the auxin pathway. True/false, if false explain why A loss-of-function mutation in the Type-A ARR protein would prevent cytokinin signaling from turning on the expression of selected genes. - Answer False, Type-A ARR protein is part of a negative feedback loop that turns 'off' cytokinin signaling by binding to and inhibiting the AHP, which is needed to phosphorylate Type-B ARR transcription regulators. A mutant with NO functional Type-A ARR would have prolonged cytokinin signaling. When ethylene binds to its receptor, ETR1, then CTR1 transfers phosphates onto EIN2. CTR1 is inactivated, so that EIN2 is cut by a protease and moves into the nucleus. EIN3 is ubiqutitinated and degraded by the proteasome. ethylene is converted into a gas. - Answer CTR1 is inactivated, so that EIN2 is cut by a protease and moves into the nucleus.