Molecular Basis of Inheritance Test - 18

Transcription is synthesis of RNA from DNA. Genetic information flows from DNA into protein, the substance that gives an organism its form. This flow of information occurs through the sequential processes of transcription (DNA to RNA) and translation (RNA to protein). During transcription, only one strand of DNA is usually copied. This is called the template strand, and the RNA molecules produced are single-stranded messenger RNAs (mRNAs).

Plant viruses often contain parasites of their own, referred to as satellites. Satellite RNAs are dependent on their associated (helper) virus for both replication and encapsidation. Satellite RNAs vary from 194 to approximately 1,500 nucleotides.

It produces a 'final draft' of the mRNA before translation gets under way. RNA splicing is the removal of introns and joining of exons in eukaryotic mRNA. It also occurs in tRNA and rRNA. Splicing is accomplished with the help of spliceosomes, which remove introns from the genes in RNA.

The pre-mRNA molecule thus goes through a modification process in the nucleus called splicing during which the non-coding introns are cut out and only the coding exons remain. Splicing produces a mature messenger RNA molecule that is then translated into a protein. Introns are also referred to as intervening sequences.

The lac operon consists of 3 structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.

If thymine is 20 % so as the adenine is also 20% , because adenine always pair with thymine therefore the percentage of adenine and thymine is  20 + 20  = 40% , thus the remaining  60% is of guanine and cytosine ., if cytosine is 30% then the percentage of guanine is also 30% because guanine is always pair with cytosine.

The relationship between the sequence of amino acid in a polypeptide and nucleotide sequences of DNA or mRNA is called genetic code. The genetic code is triplet. One codon codes for only one amino acid, hence it is unambiguous and specific. Some amino acids are coded by more than one codon, hence the code is generated.

DNA Fingerprinting involves identifying differences is some specific regions in DNA sequence called as repetitive DNA, because in these sequences a small stretch of DNA is repeated many times. These sequences normally do not code for any proteins, but they form a large portion of human genome. These sequences show high degree of Polymorphism and form the basis of DNA fingerprinting.

The central dogma of molecular biology describes the two-step process, transcription and translation, by which the information in genes flows into proteins: DNA → RNA → protein. Transcription is the synthesis of an RNA copy of a segment of DNA.