aptitudetests4me.com
Aptitude Tests 4 Me


bulletPassage Reading

bulletVerbal Logic

bulletNon Verbal Logic

bulletNumerical Logic

bulletData Interpretation

bulletReasoning

bulletAnalytical Ability

bulletBasic Numeracy

bulletAbout Us

bulletContact

bulletPrivacy Policy

bulletGoogle Privacy & Terms

bulletSite Map Page

Passage Reading and English Comprehension

All of the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharins.

Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops. Auxin, for instance, stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.

The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones. Such a hierarchy may also exist in plants. Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

86. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because

(a) it is not known exactly what functions the hormones perform
(b) each hormone has various effects on plants
(c) none of the hormones can function without the others
(d) each hormone has different effects on different kinds of plants

87. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?

(a) Plant cell walls
(b) The complement of genes in each plant cell
(c) A subset of a plant cellís gene complement
(d) The five major hormones

88. The passage suggests that which of the following is a function likely to be performed by an oligosaccharin?

(a) To stimulate a particular plant cell to become part of a plantís root system
(b) To stimulate the walls of a particular cell to produce other oligosaccharins
(c) To activate enzymes that release specific chemical messengers from plant cell walls
(d) To duplicate the gene complement in a particular plant cell

89. The author mentions specific effects that auxin has on plant development in order to illustrate the

(a) point that some of the effects of plant hormones can be harmful
(b) way in which hormones are produced by plants
(c) hierarchical nature of the functioning of plant hormones
(d) concept of pleiotropy as it is exhibited by plant hormones

90. According to the passage, which of the following best describes a function performed by oligosaccharins?

(a) Regulating the daily functioning of a plantís cells
(b) Interacting with one another to produce different chemicals
(c) Releasing specific chemical messengers from a plantís cell walls
(d) Influencing the development of a plantís cells by controlling the expression of the cellsí genes

91. The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to

(a) trace the passage of chemicals through the walls of cells
(b) pinpoint functions of other plant hormones
(c) artificially control specific aspects of the development of crops
(d) alter the complement of genes in the cells of plants

92. The author discusses animal hormones primarily in order to

(a) introduce the idea of a hierarchy of hormones
(b) explain the effects that auxin has on plant cells
(c) contrast the functioning of plant hormones and animals hormones
(d) illustrate the way in which particular hormones affect animals

TOTAL

Detailed Solution




Download Free EBooks for GMAT, GRE, ACT, SAT, LSAT, MCAT etc.

1. Passage Reading 2. Verbal Logic 3. Non Verbal Logic 4. Numerical Logic

5. Data Interpretation 6. Reasoning 7. Analytical Ability 8. Basic Numeracy

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140
141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160
161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200
201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260
261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280
281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320
321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340
341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360
361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380
381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400
401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419

Tell Your Freind

Your Name:
Your Friends Email Address:
Your Friends Name: