Rheumatoid arthritis is an example of autoimmune disease. It is a disorder where the autoimmune system of the body attacks the joints causing severe inflammation. The body fails to distinguish between foreign particles and ‘self’ cells.

Dengue leads to a reduction of platelet count. Platelets are essential for blood clotting factors. Thus a reduction of platelets leads to hemorrhagic fever due to internal bleeding.

Gobar gas has a composition of 50-70% CH₄ (Methane), 30-40% CO₂ and little amount of H2, N2 and H₂S.

When a circular plasmid is digested with a restriction enzyme having 3 sites then, the enzyme would cut the plasmid from three places which would results in 4 linear DNA fragments.

During PCR, the number of DNA molecules increases by 2ⁿ. Where 'n' is number of divisions 
Initial number of template DNA molecules in a PCR= 1000 
Total number of cycles =20 
At the end of total number of molecules of DNA after 20 cycles = 2²⁰ x 1000= 10⁹ (approx.)

Retroviruses contains enzyme reverse transcriptase or RNA dependent DNA polymerase which converts RNA TO DNA thus genetic material is RNA not DNA for e.g., Rous Sarcoma virus.

In somatic cell cycle the replication of DNA takes place in S phase which is the synthesis phase.

At metaphase the chromosomes are condensed and rare arranged in an equatorial plate and can be countttedd conveniently thus it is the best stage to study the structure of chromosomes.

Given, 

Four light weight rod samples of A, B, C, D 

And a bar magnet is brought near each of them 

Observation 

(i) A is feebly repelled 

(ii) B is feebly attracted 

(iii) C is strongly attracted 

(iv) D remains unaffected 

Paramagnetic materials will be feebly attract, diamagnetic materials will be feebly repelled and Ferromagnetic materials will be strongly attracted.

Nickel exhibits ferromagnetism because of a quantum physical effect called exchange coupling in which the electron spin of one atom interact with those of neighbouring atoms. The result is alignment of the magnetic dipole moments of the atoms, in spite of the randomizing tendency of atomic collisions. This persistent alignment is what gives ferromagnetic materials their permanent magnetism. 
If the temperature of a ferromagnetic material is raised above a certain critical value, called the Curie temperature, the exchange coupling ceases to be effective. Most such materials then become simply paramagnetic; that is, the dipoles still tend to align with an external field but much more-weakly, and thermal agitation can now more easily disrupt the alignment.

Ammonium dichromate, (NH₄)₂Cr₂O₇, decomposes when heated to produce Cr₂O₃, nitrogen gas, and water vapor. 

(NH₄)₂Cr₂O₇(s) → Cr₂O₃(s) + N₂(g) + 4H₂O(g) 

While the ammonium dichromate decomposes, it gives off orange sparks and throws the green-coloured Cr₂O₃ crystals into the air.

Bohr’s radius of hydrogen atom is 

R = n² × 0.529 A° 

For first orbital, n = 2 

R = 2.12 A°

At 22.4, water will occupy 18 mL of volume.