UGC NTA NET/JRF Exam, Forensic Science, December-2023

In forensic DNA fingerprinting analysis, the restriction enzymes Hae III, ECORI, and Hind II are commonly used. These enzymes cut DNA at specific recognition sites, creating fragments that can be analyzed through gel electrophoresis to generate unique DNA profiles.

Hae III recognizes the GGCC sequence, ECORI recognizes GAATTC, and Hind II recognizes GTYRAC. Sau3A1 and BCgi are not as commonly used in forensic DNA analysis.

The correct combination of enzymes for DNA fingerprinting includes those widely recognized for their consistent and specific cutting patterns in forensic applications.

The pH of phenol used in DNA isolation from biological exhibits is maintained above 7.5 because DNA partitions into the organic phase in the acid range, and maintaining a higher pH ensures DNA remains in the aqueous phase, facilitating its isolation.

Additionally, an alkaline pH helps remove traces of proteins, which could otherwise contaminate the DNA sample. Safeguarding RNA and separating white blood cells from other cell components are not primary concerns addressed by phenol pH.

Therefore, maintaining the appropriate pH helps in achieving pure DNA isolation by separating it from other cellular components.

The organic irritant poisons Ricinus communis, Semicarpus anacardium, and cantharides are known for causing irritation and toxic effects when ingested or contacted. Ricinus communis produces ricin, a potent toxin.

Semicarpus anacardium, commonly known as the marking nut, causes severe skin irritation. Cantharides, derived from blister beetles, contain cantharidin, which is a strong irritant.

Aconite and opium are toxic, but they are not primarily classified as irritant poisons; aconite is a neurotoxin, and opium is a narcotic. Therefore, the combination of (b), (d), and (e) accurately reflects the classification of organic irritant poisons.

The correct combination of chemical names and their synonyms includes mercuric chloride (corrosive sublimate), mercuric oxide (sipichand), and mercurous chloride (calomel lotion).

Mercuric chloride is a highly toxic compound historically known as corrosive sublimate. Mercuric oxide, known as sipichand in some contexts, is used in various applications.

Mercurous chloride, also called calomel, has been used in medicinal preparations. Mercuric sulphide is known as cinnabar, not raskapoor.

Diethyl mercury does not correspond to cinnabar, which is the common name for mercuric sulphide. Thus, (a), (b), and (e) are the correct pairings.

The proportion of unburnt powder to the whole charge depends on the length of the barrel of the weapon, the pressure, and the type of powder. The barrel length influences how completely the powder burns before the projectile exits the barrel.

The pressure within the barrel affects the combustion rate of the powder. The type of powder determines its burning characteristics, including how fast or slow it burns.

The type of projectile and the bore type have less impact on the proportion of unburnt powder compared to these factors.

The two most commonly used preservative materials added to the developing solution for the development of paper and film negatives are potassium metabisulphite and sodium sulphide.

These chemicals help preserve the developing solution by preventing oxidation and extending its usable life. Pyrogallol and catechol are developing agents, not preservatives.

Phenidone is another developing agent. Therefore, potassium metabisulphite and sodium sulphide are correctly identified as preservatives used in photographic development solutions.