Question

Suppose a translocation occurs between chromosome 14 and chromosome 21 in an individual. A translocation is the result of the fusion between two nonhomologous chromosomes. Chromosome 14 is 109 million base pairs in length, while chromosome 21 is 48 million base pairs in length. For this problem, assume that the translocation fuses the entirety of chromosome 14 to the entirety of chromosome 21. a. How long is the DNA portion of this translocation chromosome in meters? b. How many nucleosomes are found within this translocation chromosome? Assume that the average length of the linker DNA is 50 base pairs. c. How many H2A molecules would you expect to find within this translocation chromosome? d. How many radial loop domains would you expect to find within this translocation chromosome?

Answer 1

1. A chromosomal translocation is an chromosomal abnormality which occurs in non homologous chromosomes due to their improper re arrangement. Translocations can result in equal distribution of genes as well as improper distribution of genes where certain base pairs go missing during this process.

The length of the DNA portion of the translocated chromosome is 0.037metres.

The number of nucleosomes found in translocation chromosome will be

Number of bp in chromosome14 - Number of bp in chromosome 21 / 146 bp ( A nucleosome core particle consists of 146 bp)

= 417,808 number of nucleosomes.

c. The core particles in a nucleosome are connected by small stretches of DNA called linker DNA, with a length of 50bp. Every histone octomer consist of 2 molecules of core histone, H2A, H2B, H3, H4, thus the number of H2A molecules in a translocation chromosome will be 417,808 * 2 = 835,616 number of H2A molecules.

The number of radial loop domain will be half the number of nucleosome present.