Reading 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
(5) 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
(10) 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
(15) 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
(20) 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 o show that,
in a sense, cell determination begins even before an egg
(25) is fertilized.
Studying sea urchins, biologist Paul Gross found
that an unfertilized egg contains substances that func-
tion as morphogenetic determinants. They are located
in the cytoplasm of the egg cell; i.e., in that part of the
(30) 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
(35) 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
(40) 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
(45) histones move into the cell nucleus, where section of
DNA wrap around them to form a structure that resem-
bles 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
(50) DNA strings that guides the fate of the cells in which
they are located.


(1)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
(E) present in larger quantities than is necessary for the
development of a single individual


(2)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) Sythesis 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
(E) Generation of all of a cell's morphogenetic
determinants


Please explain your answers . OA to follow soon.

(1)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 - they are located outside the nucleus
(B) evenly distributed unless the embryo is not developing normally - does not say anything about normal development
(C) inactive until the embryo cells become irreversibly committed to their final function - bingo ! line 17 and 32 , hence the inference.
(D) identical to those that were already present in the unfertilized egg - Not identical - line 36
(E) present in larger quantities than is necessary for the development of a single individual - passage doesnot say anything about quantity


(2)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 - no mention or implication in the passage
(B) Sythesis of proteins called histones - produced by maternal RNAs(morph. determinants) which are inactive untill fertiliztion.
(C) Division of a cell into its nucleus and the cytoplasm - no mention or implication in the passage
(D) Determination of the egg cell's potential for division - no mention or implication in the passage
(E) Generation of all of a cell's morphogenetic determinants - morpho. deteminants are present even before fertilization.


OA please.

[spoiler]OA (1) E and (2) B [/spoiler]

I got first one as E using Process of elimination.
C can also be ruled out. The question asks about early embryo. This means, after egg fertilization. The substance becomes active just after fertilization & not when embryo cells become irreversibly committed to their final function .

What could be the level of Q1? 700+?

this_time_i_will wrote:I got first one as E using Process of elimination.
C can also be ruled out. The question asks about early embryo. This means, after egg fertilization. The substance becomes active just after fertilization & not when embryo cells become irreversibly committed to their final function .

Mate I would not worry about the level of question or what range it is .

This kind of thinking will not be very helpful to a great score . No offense mate but if you think too much about the question level , it reduces the chances of solving the question.

If the question is unique one that i have encountered I would note it down and make a list of such questions . So that in future if I encounter a similar one I would nail it .

Cheers !!!

How is 1 ) E

pink_08 wrote:How is 1 ) E

Mate I am sorry for this post , I too picked C for Q1 . But I dont trust the source so dont bother cracking your head over this one , as this answer is probably incorrect .

My sincere apologies .

Can anyone explain me why the answer to question no. 2 is B?