The main cause of spermatogenic block in the hinny is probably a failure of pairing of homologous chromosomes
which results in unfinished synapsis and incomplete meiosis.
The phenomenon of genes on the same chromosome not conforming to the principle of independent assortment was later to be called 'linkage' by Morgan (1910), and the process of segmental interchange between homologous chromosomes
, 'crossing over' (Morgan & Cattell 1912, Morgan et al.
Such aberrations often occur during pairing of homologous chromosomes
at meiosis; each chromosome from a given pair may exchange part of their genetic material.
This is due to the random segregation of homologous chromosomes
and chromatid exchange among homologues during the first meiotic prophase.
The following analogy may help you visualize homologous chromosomes
Genetic linkage is symbolized with either a single straight line or a single forward slash separating the genes that reside on different members of a pair of homologous chromosomes
, for example,
Although eight CS-B lines had significantly lower boll weight than TM-1; additive effects for chromosomes 4, 6, and 15sh from 3-79 were significantly greater than additive effects for homologous chromosomes
in TM-1; whereas, additive effects for boll weight for chromosomes 18, 25, 05sh, 14sh, 22sh, and 22Lo from 3-79 were less than the homologous chromosomes
The noise appears to be related either (1) to inconsistency in the quality of repetitive sequence-enriched DNA required for assay specificity or (2) to copy-number polymorphisms that are found in homologous chromosomes
from the same and from different individuals.
The degree of difference is determined largely by the characteristics of the homologous chromosomes
(those that associate in pairs during meiosis).
During meiosis, homologous recombination between neighboring transposable elements at nonhomologous positions on homologous chromosomes
would result in unequal exchange of chromatin lying between these sequences.
8S, and 28S ribosomal RNAs (Ritossa and Spiegelman, 1965; Howell, 1982), they have been useful for identifying homologous chromosomes
within and among cyprinid complements.
My proposal combines three innovative and complementary approaches towards understanding how homologous chromosomes
are segregated and why oocyte maturation in mammals is so error-prone.