Cell Cycle and Chromosomes

In meiosis, chiasma represents the site of crossing over.

Karyokinesis is the process of division of nucleus.

Centromere is present on a chromosome.

The poleward movement of chromatids of the chromosomes takes place during this phase.

Centromere is in the centre so the arms are equal in length. 

Alleles are always present on the same locus of homologous chromosomes for crossing over.

This division involves recombination due to which this step is unique to meiosis.

Spindles get organised and the chromosomes get arranged in the equatorial plate.

These are the thread like structures which condense into chromosomes during prophase.

It is the aberration in which a segment detaches, gets inverted and rejoins the main chromosome.

 Both Assertion and Reasoning are true and R is the correct explanation of A. If karyokinesis is not followed by cytokinesis the cell becomes multinucleate or coenocytic or syncytial. Striated muscle fibers show striations with many nuclei in their striations. It shows syncytial condition.

If a chromosome segment gets inserted in interstitial position of a non-homologous chromosome, it is known as shift translocation. In humans, it is invariably associated with myelogenous leukemia.

This type of mutation takes place between two chromosomes and interchanges their chromosome segments. In other words, a portion of chromosome is transferred on to other chromosome.

ZNF259 where the gene ZNF259 plays an important role as a signaling molecule. ZNF259 communicates mitogenic signals from the cytoplasm to the nucleus and interacts with tyrosine kinase receptors.

This state results from an abnormal swap over of genetic material between chromosomes. This swap over occurs as a chance event in the father of an affected person during the formation of sperm cells. The translocation affects the gene in charge that is SRY for development of a fetus into a male.