Chromosome Changes in Soma and Germ Line: Heritability and Evolutionary Outcome

Abstract

The origin and inheritance of chromosome changes provide the essential foundation for natural selection and evolution. The evolutionary fate of chromosome changes depends on the place and time of their emergence and is controlled by checkpoints in mitosis and meiosis. Estimating whether the altered genome can be passed to subsequent generations should be central when we consider a particular genome rearrangement. Through comparative analysis of chromosome rearrangements in soma and germ line, the potential impact of macromutations such as chromothripsis or chromoplexy appears to be fascinating. What happens with chromosomes during the early development, and which alterations lead to mosaicism are other poorly studied but undoubtedly essential issues. The evolutionary impact can be gained most effectively through chromosome rearrangements arising in male meiosis I and in female meiosis II, which are the last divisions following fertilization. The diversity of genome organization has unique features in distinct animals; the chromosome changes, their internal relations, and some factors safeguarding genome maintenance in generations under natural selection were considered for mammals.

Reorganization, specialization, and degradation of oocyte maternal components for early development

“…Therefore, unfertilized oocytes are commonly called MII oocytes. 24 , 25 , 26 The GV to MII oocyte maturation can be induced in vitro in a process called in vitro maturation (IVM). The major difference between sperm and oocyte differentiation in mammals is that spermatozoa complete meiosis to be haploid in the testis, whereas the oocyte does not complete meiosis in the ovary.…”

“…The ovulated oocyte of mice and humans stops in metaphase of the second meiotic division (MII) to await the sperm in the oviduct. Therefore, unfertilized oocytes are commonly called MII oocytes 24–26 . The GV to MII oocyte maturation can be induced in vitro in a process called in vitro maturation (IVM).…”

Improved mRNA electroporation into immature oocytes to examine protein dynamics during development

“…The ovulated oocytes of mice and humans arrest their cell cycles and cellular dynamics again in the metaphase of the second meiotic division (MII), awaiting the sperm to be fertilized in the oviduct. Unfertilized oocytes are thus called MII oocytes (Bakloushinskaya, 2022; Conti and Franciosi, 2018; Zielinska et al, 2019). The transition from a GV to an MII oocyte is called oocyte maturation and can be induced in vitro with an in vitro maturation (IVM) treatment.…”