Differentiate between the followings:
(a) Repetitive DNA and Satellite DNA
(b) mRNA and tRNA
(c) Template strand and Coding strand

Explanation

(a) DNA fingerprinting requires identification of variations among particular areas in DNA sequences known as repititve DNA. In such sequences, a small part of DNA is repeated several times. Such repetitives DNA are seprated from bulk genomic DNA in the form of different peaks during the process of density gradient centrifugation. DNA present in bulk is exhibited in the form of major peaks and remaining which appear in the form of small peaks are called as satellite DNA. Satellite DNA is of many types like micro-satellites, mini-satellites. Such classification has been made on the basis of : (i) Base composition e.g. A : T rich or G : C rich, (ii) Length of segment and (iii) Number of repetitive units.
mRNA and tRNA
Template strand and coding strand
DNA dependent RNA polymerase is capable to catalyze only in 5. - 3. direction. Due to this reason DNA strand with polarity 3. - 5. acts as a template strand. During the process of transcription, second strand of DNA is with 5. - 3. (with the same sequence of polymers in RNA). However in RNA strand, uracil is present in place of thymine. This DNA strand, which is taking part in transcription is displaced. Interestingly this non-coding strand of DNA is called coding strand.