How Does It Affect The Basic Structures Of Chromosomes?

874 Words4 Pages
Discussion From the image is can been seen that some bands are lightly stained and some are darkly stained it might be of two reasons: 1 G banding techniques enhances the basic structures of chromosomes. The chromosomes consists of 8 histones proteins molecules , each of which is wrapped around by DNA of 146bp long to form a repeating units called nucleosomes, then successive nucleosomes are arranged to form a structure similar to that of beads of a string which again coil themselves to form chromatin fiber. Chromosome package is form when chromatin fiber are further loop and coiled. 2. the difference in staining might also be due to the difference in functional constituents of DNA in different regions of chromosomes, since G-banding is carried out in the metaphase, it has been shown in the studies of replication that regions of DNA that are replicating at similar time tends to clustered together, this type of chromosome will stain darker as more basic dye will get attracted towards this region as this area consist of higher concentration of DNA and DNA carries negative charge. This proves that the dark G-bands replicate lately than the light bands as they have already break the cluster and finish replicating in the S-phase. Moreover, it has been proven by in-situ hybridization technique that dark G-band consists mostly of L1-type repetitive DNA sequences which are rich in AT and are responsible for encoding few expressed gene while light G-bands constituents are mostly

More about How Does It Affect The Basic Structures Of Chromosomes?

Open Document