A cruciform structure of chromosomes during meiosis is a characteristic feature of:

🔑Key Points:
-A chromosomal abnormality, or chromosomal aberration refers to any disorder that is characterized by a morphological or numerical change in single or multiple chromosomes, that affects autosomes, sex chromosomes, or both.
Types of chromosomal aberration – 

✏️Deletion:
-Deletion refers to the loss of a segment of a chromosome.
-It can be of two types: terminal and interstitial.
-Terminal deletion involves a single break while interstitial deletion rinvovled two breaks. 
-Generally deletion is lethal because it causes genetic imbalance in diploid organisms. 

✏️Duplication:
-Duplication refers to occurence of a segment of DNA of a chromsomes in two or more copies per genome. In this case, the duplicated segments can be located next to one another or they can be dispersed on the same chromosome.  
-It is produced as the result of abnormal events during recombination. 
-It can be of two types – direct and inverted. 
-In direct duplication, the duplicated segments keeps the same orientation with respect to the centromere.
-In inverted duplication, the duplicated segments takes the opposite orientation.
-Inversion: 
-Inversion is a type of chromosomal mutation that results in a change in the nucleotide sequence of a gene or a chromosome.
-It starts with two double-stranded breaks within a segment of chromosomes.Then entire fragment is rotated end-to-end between the fracture lines, and the re-fusion of the fragment. 
-This causes a change in the order of the genes in the section that is inverted. 
-Chromosomal inversion is of two types – 
-Paracentric inversion: It does not involve the centromere and only one arm of the chromosome has two breaks.
-Pericentric inversion:  It involves a centromere with each arm having one double-stranded break.
-Translocation: 
-Translocation refers to exchange of chromosomal segments between two non-homologous chromosomes. 
-It can be of two types: reciprocal and non-reciprocal.
-Non-reciprocal translocation involves the transfer of segment in one direction from one chromosome to another. 
-Reciprocal translocation involves exchange of the segments of chromosomes between non-homologous chromosomes, this results in the generation of two translocated chromosomes simultaneously. 

✅ Explanation:
-Translocation typically affects the product of meiosis. 
-In the strains that are homozygous for a reciprocal translocation, meiosis occurs normally, all chromosomes can pair and crossing over does not leads to the production of abnormal chromatids. 
-In the strains that are heterozygous for a reciprocal translocation, then all the homologous chromosomes pairs in best way possible this leas to generation of cross-like (cruciform) configuration in meiotic prophase I. 
-So, cruciform structure is seen in the event of reciprocal translocation that takes place during meiosis process.