Explore topic-wise InterviewSolutions in Current Affairs.

1. Mycoplasma (0.3 µm) 

2. Nerve cell 

3. Ostrich egg

1. The bacterial shapes observed by the students are cocci, bacilli, vibrios, spirilla. 

2. Under microscope, cocci appear spherical shape, bacilli appear rod shape, vibrios appear comma shape and spirilla appear twisted, therefore they are named accordingly.

1. The postulate Ananya was willing to test was, ‘all cells arise from pre-existing cells’. According to this postulate, to form new cells, pre-existing cells are must; therefore, cellular organelles did not form new cells. 

2. The cells which Ananya and her teacher were trying to form were eukaryotic cells, as cellular organelles are present in eukaryotes.

The Gram-positive bacteria show presence of peptidoglycan layer in the cell wall and Gramnegative bacteria show presence of murein in the cell wall. The technique used for differentiating bacterial cells is Gram staining. [Note: Murein is similar to peptidoglycan in structure and function. It is present in the cell walls of archaebacteria.

1. Ribosomes are protein factories of cell and were first observed as dense particles in electron micrograph of a cell by scientist Palade in 1953. 

2. Ribosomes lack membranous covering around them and are made up of Ribosomal RNA and proteins. 

3. In a eukaryotic cell, ribosomes are present in mitochondria, plastids (in plant cells) and in cytosol. 

4. Ribosomes are either found attached to outer surface of Rough Endoplasmic Reticulum and nuclear membrane or freely suspended in cytoplasm. 

5. Both are of 80S type. Each ribosome is made up of two subunits- a large (60S) and a small (40S) subunit. 

6. Bound ribosomes generally produce proteins that are transported outside the cell after processing in ER and Golgi body. e.g. Bound ribosomes of acinar cells of pancreas produce pancreatic digestive enzymes.

7. Free ribosomes come together and form chains called polyribosomes for protein synthesis. 

8. Free ribosomes generally produce enzymatic proteins that are used up in cytoplasm, like enzymes required for breakdown of sugar.

9. Both types of ribosomes (bound and free) can interchange position and function. 

10. Number of ribosomes is high in cells actively engaged in protein synthesis.

There is no typical shape of a cell. Cells may be spherical, rectangular, flattened, polygonal, oval, triangular, conical, columnar, etc.

General characteristics of prokaryotic cell: 

1. Prokaryotic cells are primitive type of cells. 

2. It does not have membrane bound cell organelles (like endoplasmic reticulum, Golgi complex, mitochondria, etc.) and well-defined nucleus (nuclear membrane is absent). 

3. Genetic material is in the form of nucleoid. 

4. Cell envelope: 

a. Prokaryotic cell has chemically complex protective cell envelope having glycocalyx, cell wall and plasma membrane. 

b. In some bacteria, glycocalyx occurs in the form of a slime layer (loose sheath). Other bacteria may have a thick and tough covering called capsule. It helps in protection of bacterial cell. 

5. Cell wall: 

The Gram-positive bacteria show presence of peptidoglycan layer in the cell wall and Gramnegative bacteria show presence of murein in the cell wall. It gives mechanical strength to the cell. 

[Note: In Gram-negative bacteria, cell wall is made up of two layers; inner layer of Murein or peptidoglycan and outer layer of Lipopolysaccharides.]

6. Cell membrane: 

a. It is the innermost covering of the cell envelope, chemically composed of lipids and proteins. 

b. It helps in intercellular communication. 

c. Cell membrane shows infoldings called mesosomes which help in cell wall formation, cellular respiration and DNA replication. 

d. The cyanobacteria show longer extensions called as chromatophores which carry photosynthetic pigments. 

7. In motile bacteria either cilia or flagella are found. Both are driven by rotatory movement produced by basal body (which works as motor) of flagellum. Other parts of flagellum are filament and hook. 

8. Some other surface projections are the tubular pili (which help in inter-cellular communication) and fimbriae (for clinging to support).

9. Ribosomes: Bacterial cell cytoplasm contains dense particles called ribosomes which help in protein synthesis. Ribosomes are 70S type (composed of a larger sub-unit 50S and + smaller sub-unit 30S).

1. To observe cells or organisms of smaller size we use a microscope. 

2. Larger cells can be seen through simple microscope but to observe smaller cells we require compound microscope. 

3. Simple microscope can magnify image 50 to 100 times but a compound microscope can do so 1000 times or more. 

4. In the microscope a beam of light is used to make things visible hence it is light microscope. 

5. To observe interior of cell we need electron microscope which can magnify image 500000 times.

Living organisms are grouped into two main categories the Prokaryotes and Eukaryotes.

Some of the main objections raised against Darwinism are as follows:

• There are other factors too for evolution and just not the Natural Selection.
• Arrival of useful and useless modifications were not explained by Darwin, though he said about the survival of the fittest.
• He has not given any explanation about slow changes and abrupt changes occurring during evolution.

Stromatolites are the colonies of cyanobacteria bind with Calclum carbonate.

i. 1 (T)

ii. 1 (TR)

iii. 2 (TR, Tr)

iv. 2 (T, t)

v. 2 (TRb, tRb)

vi. 4 (TR, Tr, tR, tr)

vii. 4 (TRBaD, TRBad, tRBaD, tRBad)

 Correct Option is (B) segregation

 Correct Option is (B) hybrid x recessive parent (Tt x tt)

The cross between F₁ hybrid and any one of the parents is called back cross.

(A) recessive homozygous

The disease sickle-cell anaemia is caused by a gene Hb^S which is recessive. A marriage between two carriers of sickle-cell anaemia (Hb^A Hb^S) will produce – normal children with genotype (Hb^AHb^A), sickle cell carriers with genotype (Hb^AHb^S) and sickle-cell anaemic with genotype Hb^SHb^S . Sickle-cell anaemic dies leaving behind carriers and normal. Thus, the gene for sickle-cell anaemia (recessive gene) is lethal in homozygous condition.

The cross between F₁ hybrid and the recessive parent is called test cross.

Law of segregation is universally applicable.

Member of allelic pair in a hybrid remain together without mixing with each other and separate or segregate during gamete formation. Thus gametes receive only one of the two factors and are pure for a given trait. Therefore, this is also known as law of segregation.

All sexually reproducing higher organisms are diploid (2n), i.e. with two sets of chromosomes and gametes are haploid (n), i.e. with one set of chromosome. Therefore, law of segregation is universally applicable.

Law of dominance is not universally applicable.

In a cross between two organisms pure for any pair (or pairs) of contrasting characters, the character that appears in F₁ generation is called dominant and the one which is suppressed is called recessive. In many cases, the dominance is not complete or absent. Phenomenon of dominance is significant as the harmful recessive traits are masked, i.e. not expressed in the presence of its normal dominant allele. e.g. In humans a form of idiocy, diabetes and haemophilia are recessive characters. Thus, law of dominance is significant and true, but it is not universally applicable.

A back cross with dominant parent is not a test cross.

Test cross is a back cross but back cross is not necessarily a test cross.

It is because; in back cross F₁ generation can be crossed with either dominant or recessive parent. But in test cross, F₁ generation is crossed with recessive parent only. Thus, test cross is a back cross but back cross is not necessarily a test cross.

Significance of back cross:

i. It is a rapid method of improving crop variety.

ii. It helps to verify laws of inheritance.

iii. Back cross with dominant parent always produce dominant characters.

iv. Continuous back cross never produce recessive trait, hence recessive trait can be eliminated from progeny.

(C) recessive gene

Genotype of albino person is aabbcc (pure white, melanin is not produced at all).

Difference between Test cross and Back cross:

ABO blood group in human being is an example of multiple allelism.

There alleles for the gene I  i.e. I^A,I^B,i.

When I^A and I^B are present together the blood  group is AB.

Both A and  B. are expressed and is called codominance.

Detailed Answer: 

ABO blood grapes in human population is an example of multiple allelism and codominance. There are three alleles of gene l, i.e., I^A,I^B and i. thus exhibiting multiple alIelism. Out of these three alleles any two alleles may occur in human being, one alleles is contributed from each parent.

The alleles I^A + I^B are dominant over allele i and produce A and B phenotypes respectively. But however when alleles I^A and I^B are present together both of them express equally and independently producing AB phenotype. This is a phenomenon called codominance.

Snapdragon (Antirrhinum majus) and Four o’clock plant (Mirabilis jalapa) show incomplete dominance.

Functional adenosine deaminase is given to the patient by injection.

i. Lymphocytes from the blood of the patient are grown on culture outside the body.

ii. A functional ADA, cDNA is then introduced into these lymphocytes using a retroviral vector.

iii. The genetically engineered lymphocyte are returned to the blood of patient.

Disadvantages: Therapy is not completely curative as cells do not remain alive and periodic infusion of lymphocytes is required.

Difference between the Incomplete dominance and Co-dominance:

One gene I has three alleles I^A,  I^B and i hence multiple allelism. We inherit any two of them. When the genotype is   I^A I^B, the individual has AB blood group since both I^A and I^B equally influence the formation of Antigen A and B- Co-dominance.

Detailed Answer : 

(a) Multiple allelism is the phenomenon of occurrence of a gene in more than two allelic forms on the same locus homologous pair chromosome. In ABO blood group in humans one gene I has three alleles I^A, I^B and i. 

Co-dominance is the phenomena in which both alleles of a gene express themselves when present together. We inherit any two of the three alleles for the blood group. When the genotype is I^AI^B the individual has AB blood group since both I^A and I^B equally influence the formation of antigens A and B.

Correct option is  D) 2n²

In the process of distillation,

A liquid is converted into its vapour and the vapour is then condensed back to liquid on cooling. 

The condenser has a jacket with two outlets through which water is circulated. 

Hence,

To provide efficient cooling, a condenser is used.

Correct option is  D) N

Before filtration,

Filter paper is moistened with appropriate solvent to ensure that it sticks to the funnel and does not let the air to pass through the leaks.

Impurities which are not soluble in the same solvent as the main compound can be separated by a simple process called filtration. 

Hence,

For ‘Case 2’, filtration is more feasible.

Kr (Z=36)e.c is 1s² ,2s² ,2p⁶ ,3s² ,3p⁶ ,4s² ,3d¹⁰,4p⁶ . 

2p⁶ orbital has same energy as3s² , &3d¹⁰ orbital has same energy as 4p⁶ etc.  

No, the energy depends upon (n+l) values in an atom. Hence 2p orbital has greater energy than 2s.

D) all of these

Correct option is c. tetrahedral, sp³

Distillation technique can be employed for the purification of :

• volatile liquids from non-volatile impurities.
• liquids having sufficient difference in their boiling point.

Correct option is D) 4f

Forces acting on an object which tend to change the state of rest or of uniform motion of it are called unbalanced forces.

Correct answer is (d) point

These are a class of psychedelic drugs which affect cerebrum and sense organs to alter thought, feeling and perception, e.g., LSD (lysergic acid diethyl amides) and emphetamines. Clinically they are used to treat depression and insomnia.

Fractional crystallization is based on the differences in solubilities of two or more compounds in the same solvent at the same temperature. That is, the substance which is least soluble crystallizes out first and the most soluble substance crystallizes out last. 

e.g. Mixture of two solutes A and B can be purified by fractional crystallization as follows :

• Preparation of a saturated solution : Mixture of two solutes A and B are dissolved in a suitable hot solvent to prepare a saturated solution.
• Hot filtration : The hot saturated solution is filtered to remove insoluble impurities.
• Cooling of the filtrate : Hot filtrate is allowed to cool. On cooling, the solute which is least soluble crystallizes out first leaving behind the most soluble substance in the mother liquor.
• Filtration : The crystals formed are filtered, washed with solvent and dried. Crystals obtained will be of a solute which is least soluble in a given solvent.
• Concentration of a mother liquor : The mother liquor is concentrated by evaporating the solvent. These crystals are filtered and dried to obtain the second purified component (which was more soluble in given solvent).

Option : (A) crystallization

A system can be brought to equilibrium by applying another force, which is equal to the resultant force in magnitude, but opposite in direction. Such force is called as ‘Equilibriant’.

a. By the contact inhibition property, normal cells do not change into cancerous cells. 

b. Several genes called cellular oncogenes (c-onc) or proto-oncogenes in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells leading to cancer.

Water of crystallization is the fixed number of water molecules present in one formula unit of salt.

(i) Five molecules of water.

(ii) Formula -CuSO₄.5H₂O

(iii) When heated, its colour changes from blue to white.

Two equal and unlike parallel forces applied simultaneously at two distinct points constitute a couple. The line of action of the two forces does not coincide. 

Eg: Turning a tap, winding or unwinding a screw, spinning of a top, etc.