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

Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos. This led them to believe that the cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways. Later biologists found that the situation was not so simple. It matters in which plane the embryo is cut. If it is cut in a plane different from the one used by the early investigators, it will not form two whole embryos.

A debate arose over what exactly was happening. Which embryo cells are determined, just when do they become irreversibly committed to their fates, and what are the “morphogenetic determinants” that tell a cell what to become? But the debate could not be resolved because no one was able to ask the crucial questions in a form in which they could be pursued productively. Recent discoveries in molecular biology, however, have opened up prospects for a resolution of the debate. Now investigators think they know at least some of the molecules that act as morphogenetic determinants in early development. They have been able to show that, in a sense, cell determination begins even before an egg is fertilized.

Studying sea urchins, biologist Paul Gross found that an unfertilized egg contains substances that function as morphogenetic determinants. They are located in the cytoplasm of the egg cell; i.e., in that part of the cell’s protoplasm that lies outside of the nucleus. In the unfertilized egg, the substances are inactive and are not distributed homogeneously. When the egg is fertilized, the substances become active and, presumably, govern the behavior of the genes they interact with. Since the substances are unevenly distributed in the egg, when the fertilized egg divides, the resulting cells are different from the start and so can be qualitatively different in their own gene activity.

The substances that Gross studied are maternal messenger RNA’s—products of certain of the maternal genes. He and other biologists studying a wide variety of organisms have found that these particular RNA’s direct, in large part, the synthesis of histones, a class of proteins that bind to DNA. Once synthesized, the histones move into the cell nucleus, where section of DNA wrap around them to form a structure that resembles beads, or knots, on a string. The beads are DNA segments wrapped around the histones; the string is the intervening DNA. And it is the structure of these beaded DNA strings that guide the fate of the cells in which they are located.

782. The passage is most probably directed at which kind of audience?

(a) State legislators deciding about funding levels for a state-funded biological laboratory
(b) Scientists specializing in molecular genetics
(c) Readers of an alumni newsletter published by the college that Paul Gross attended
(d) Marine biologists studying the processes that give rise to new species

783. It can be inferred from the passage that the morphogenetic determinants present in the early embryo are

(a) located in the nucleus of the embryo cells
(b) evenly distributed unless the embryo is not developing normally
(c) inactive until the embryo cells become irreversibly committed to their final function
(d) identical to those that were already present in the unfertilized egg

784. The main topic of the passage is

(a) the early development of embryos of lower marine organisms
(b) the main contribution of modern embryology to molecular biology
(c) the role of molecular biology in disproving older theories of embryonic development
(d) cell determination as an issue in the study of embryonic development

785. According to the passage, when biologists believed that the cells in the early embryo were undetermined, they made which of the following mistakes?

(a) They did not attempt to replicate the original experiment of separating an embryo into two parts
(b) They did not realize that there was a connection between the issue of cell determination and the outcome of the separation experiment
(c) They assumed that the results of experiments on embryos did not depend on the particular animal species used for such experiments
(d) They assumed that different ways of separating an embryo into two parts would be equivalent as far as the fate of the two parts was concerned

786. It can be inferred from the passage that the initial production of histones after an egg is fertilized takes place

(a) in the cytoplasm
(b) in the maternal genes
(c) throughout the protoplasm
(d) in the beaded portions of the DNA strings

787. It can be inferred from the passage that which of the following is dependent on the fertilization of an egg?

(a) Copying of maternal genes to produce maternal messenger RNA’s
(b) Synthesis of proteins called histones
(c) Division of a cell into its nucleus and the cytoplasm
(d) Determination of the egg cell’s potential for division

788. According to the passage, the morphogenetic determinants present in the unfertilized egg cell are which of the following?

(a) Proteins bound to the nucleus
(b) Histones
(c) Maternal messenger RNA’s
(d) Cytoplasm (E) Nonbeaded intervening DNA

789. The passage suggests that which of the following plays a role in determining whether an embryo separated into two parts will develop as two normal embryos?

I. The stage in the embryo’s life at which the separation occurs
II. The instrument with which the separations is accomplished
III. The plane in which the cut is made that separates the embryo

(a) I only
(b) II only
(c) I and II only
(d) I and III only

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: