Which chromosomal defect is caused when part of a chromosome breaks off and reattaches backward on the same chromosome?

Translocation

Explanation:

Translocation is a chromosomal defect in which part of a chromosome breaks off and reattaches backward on the same chromosome.

Translocation can happen due to many reasons like:

A) Some of the changes that arise around the time of conception  or production of sperm or egg.

B) The inheritance of altered chromosome from father or mother.

Translocations can be divided into two forms:

In reciprocal translocations,  fragments of two chromosomes break off from two different places, break and swap each other's segments. While in  Robertsonian translocation one chromosome attached with other.

Hope it help!

lysosome is this part of the cell is surrounded by a very thick outer membrane to protect the rest of the cell from its strong enzymes.