Tag: gene cloning

Retroviruses, though have single-stranded RNA genomes but provide perhaps the most promising vector system of all. During the process of reverse transcription, sequences from the termini of viral RNA are duplicated to generate long terminal repeats(LTRs). These long terminal repeats contain both the promoter and the polyadenylation signal for the transcription of viral mRNAs. The specificity of proviral DNA integration is also determined by the long terminal repeats. Although retroviruses can integrate at many sites within the cellular genome, integrative recombination always occurs at particular sites at the ends of the LTRs. The sequences appropriately inserted between the two LTRs will be integrated intact which contrasts sharply with the integration of papovavirus or adenovirus DNA, during which extensive rearrangements of the integrated viral sequences are commonplace. A further great advantage of retroviruses is that they are natural transducing viruses.

Cloning is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. The term clone is used in horticulture to refer to descendants of a single plant which were produced by vegetative reproduction. Many horticultural plant cultivars are clones, derived from a single individual, multiplied by some process other than sexual reproduction.

Dolly was a female domestic sheep, and the first mammal cloned from an adult somatic cell, using the process of nuclear transfer ie, cloning me.method called Somatic Cell Nuclear Transfer or SCNT. A clone has the same DNA sequence as its parent and so they are genetically identical. In SCNT, the nucleus of an egg cell is removed and replaced with the nucleus of a donor adult cell. Since 99.9% of the cell’s DNA is contained in the nucleus, the resulting animal will share almost exactly the same DNA as the original donor cell. So, the correct answer is option B.

Adenosine deaminase deficiency SCID, commonly called ADA SCID, is a very rare genetic disorder. It is caused by a mutation in the gene that encodes a protein called adenosine deaminase (ADA).