BIO 101 | Study Mode

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Question 61
A
ribosomes and rRNA
B
only rRNA
C
peroxisomes
D
several ribosomes held together by string of rnRNA.
Explanation
Polyribosomes are aggregates of several ribosomes held together by string of mRNA. Polyribosomes consist of 4 8 ribosomes which are attached to a single strand of messenger RNA or mRNA. This mechanism helps in synthesis of several copies of the same protein.

Correct option: D
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Question 62
A
nucleoplasm
B
nuclear envelope
C
nucleolus
D
cytoplasm.
Explanation
Nucleoproteins are compounds present in cells of living organisms that consists of nucleic acids with proteins. Nucleoproteins are synthesized in cytoplasm. These are conjugated proteins. They is of two types Deoxyribonucleoproteins and ribonucleoproteins.

Correct option: D
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Question 63
A
two chromatids and one centromere
B
two chromatids and two centromeres
C
four chromatids and two centromeres
D
four chromatids and four centromeres.
Explanation
A bivalent consist of four chromatids and two centromeres. Bivalent is a pair of homologous chromosome lying together in the zygotene stage of prophase I of first meiotic division.

Correct option: C
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Question 64
A
numerical aperture
B
focal length of objective
C
focal length of eye piece
D
tube length.
Explanation
Magnification of compound microscope is not connected with numerical aperature. The magnifying power is represented by the symbol X. The total magnification of a microscope is obtained by multiplying the objective magnification and ocular lens magnification e.g., if the magnifying power of an ocular lens is 1 OX and of the objective is 40X, then the total magnifying power of a microscope is 10 x 40 = 40).

Correct option: A
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Question 65
A
lamellar model
B
unit memorane model
C
fluid mosaic model
D
molecular lipid model.
Explanation
The latest model of plasmamembrane is Fluid Mosaic Model. It was discovered by Singer and Nicolson, 1972. The membrane is a continuous lipid bilayer having integral protein molecules. The two are so dispersed that they form a mosaic pattern. The membrane is semifluid in nature and hence the lipid molecules and intrinsic proteins move freely.

Correct option: C
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Question 66
A
cytoplasm
B
nucleus
C
rhizoid and stalk
D
gametes.
Explanation
Hammerlings experiments with the single celled green algae, Acetabularia,showed that the nucleus of a cell contains the genetic information that directs cellular development. <br /> Each Acetabularia cell is composed of 3 segments, the foot or base which contains the nucleus, stalk and the cap. In his experiments, he grafted the stalk of one species of Acetabularia onto the foot of another species. <br /> In all cases, the cap that eventually developed on the grafted cell matched the species of the foot rather than that of stalk. This experiment shows that the base is responsible for the type of cap that grows and nucleus directs cellular development.

Correct option: C
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Question 67
A
Electromagnetic lenses
B
Very low wavelength of electron beam
C
Low wavelength of light source used
D
High numerical aperture of glass lenses used.
Explanation
Electron microscope has a high resolution power. This is due to very low wavelength of electron beam (0.005 mu) of the electron beam used as light source. It is produced when a metal filament is heated in a vaccum tube at high temperature, i.e., 50,000 volts.

Correct option: B
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Question 68
A
distinguish two close points
B
distinguish two close objects
C
distinguish amongst organelles
D
magnify image.
Explanation
Resolution power is the ability to distinguish two close objects. It is the ability of a system to distinguish two close points as two separate points. Resolving power of microscope depends upon the numerical aperture of the objective lens system and its wavelength.

Correct option: B
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Question 69
A
Danielli and Davson
B
Singer and Nicolson
C
Garner and Allard
D
Watson and Crick.
Explanation
Fluid mosaic model was put forward by Singer and Nicolson (in 1972, 74). Lipids and intrinsic proteins form a mosaic pattern. The membrane is semi fluid in nature and hence the lipid molecules and intrinsic proteins move freely.

Correct option: B
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Question 70
A
Golgi
B
De Robertis
C
Porter
D
Palade.
Explanation
Ribosomes are minute cellular, non-membranous particles having an average diameter of 23 mm (230 A0). <br /> In plant cells ribosomes were first of all observed by Robinson and Brown (1953) in bean roots. In animal cells, these were discovered by Palade (1955), hence are called Palade particles. Ribosomes form a part of fraction microsome, a term given by A, Claude (made of broken ER, ribosomes and Golgi bodies).

Correct option: D

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