Molecular Basis of Inheritance Test - 22

DMD is the longest known human gene, composed of 79 coding exons spanning 2 mega bases of the genome, with various transcriptional start sites.

One of the template DNA strands is oriented 3' to 5' at the replication fork, and it can be copied continuously by a DNA polymerase extending the new DNA chain in a 5’ to 3’ direction.

1.  This new DNA chain is called the leading strand. However, the DNA polymerase cannot synthesize DNA in 5’ to 3’ direction. Since the other template strand is oriented in 5’ to 3’ the second strand is synthesized in a discontinuous fashion and this strand is called the lagging strand.

2.  Thus, one strand is synthesized continuously and the other discontinuously so it is semi-discontinuous synthesis.

Allactose is an isomer of lactose and is the inducer of the lac operon.

HIV being as retrovirus deviates from the central dogma instead of creating proteins from DNA; it uses its host cell to create DNA from the virus's own RNA.

In three dimensions, tRNA adopts an "L" shape.

5-bromouracil is the brominated form of Uracil which gets incorporated in the DNA in the place of Thymine. Thus, Adenine can pair with 5-bromouracil instead of Thymine and this may induce point mutation.

Autoradiography is the study of labelled precursors like 3H by knowing the movement of radioactivity with the help of photographic films and emulsions at short intervals. 14C and 3H are incorporated in bases like thymidine, uridine and amino acids to study the structure of DNA and proteins. Radio tracer technique shows that DNA is in double helical form.

An octamer of 4 histones complexed with DNA forms Nucleosome. The association of histones with DNA is very characteristic. It involves the formation of linear array of spherical structures called Nucleosome.

These structures contains four pairs of histones (HA, H2B, H3 and H4) in a ball; around which is wrapped a stretch of about 150 base pairs of DNA.