Chromosomes
Published February 15th, 2025 under Rebirth X
BACKGROUND
Chromosomes themself are compacted DNA(genes), with a human having 23 pairs. 1 of which is the vital sex chromosomes (XY, XX), responsible for regulating and determining birth gender.
Within the cells of the body, the chromosomes are contained within the cell nucleus* alike majority of genetic information. Chromosomes have control over hormone levels, fertility, gender related bodily processes (menstruation, etc), and more.
Even small chromosomal changes can have large biological effects due to their genetic value. Examples of chromosomal disorders are trisomy 21* and turner syndrome, both having significant effects on the individual.
WHAT ARE THE SEX CHROMOSOMES?
Sex chromosomes refer to 1 of the 23 chromosome pairs normally found in humans. They come in both X and Y forum, with biological females having the pair XX while biological males have XY. Both of these chromosomes serve different purposes, regulating the body differently.
The way the chromosomes are "assigned" are due to randomization of the inherited genetics from parents. Your biological father has the chromosome pair XY due to being male, and your biological mother XX. It is randomized whichever you will inherit, with the male genetically deciding the gender (X chromosomes are identical to one another, so it makes no difference which of your mothers 2 X chromosomes you inherit).
Y CHROMOSOME
The unique genes within the Y chromosome allows it to regulate and initiate male development. This is primarily due to the chromosome containing the sex determining region Y gene (SRY gene). The SRY gene contains directions on how to create the sex determining region Y protein, allowing for typical male development [1]. This protein binds onto specific regions of DNA allowing for precise activity control of genes. They eventually go on to guide the development of testes and various other aspects of male exclusive anatomy during fetal development. [2]
Y chromosomes additionally contain less genetic information than X chromosomes. Research is showing that the Y chromosome is gradually losing genetic material generation by generation, as it previously contained the same amount of genetic material as the X chromosome [4]. This is due to many complex factors, including XY sex chromosome recombination (that has largely stopped). To keep this brief, the recombination was the exchange of genetic material between the two chromosomes. The Y chromosome eventually went on an evolutionary path that led it to begin independent, separate growth. This recombination has largely paused except for one small portion of gene that still exchange to this day. [5]
X CHROMOSOME
The X chromosome is extremely foundational within the bodies internal structure. It is vital enough it is responsible for up to 5% of total DNA in a cell, containing 155 million DNA base pairs and 900-1400 genes [3]. Additionally In early embryo development, individuals with 2 X chromosomes (genetic females) undergo a process called X-inactivation (also known as lyonization, named after it's founding scientist Mary .F Lyon [6] ).
This process ensures genetic uniformity and stability, reducing the potency of one of the X chromosomes to prevent an excess of genetic information. But, the suppression of either X chromosome is randomized in each cell. This results in some cells having say the genetic mothers X chromosome whereas others carry the biological dad's [3]. There's additional variability, as some cells escape this process entirely.
GENETIC MUTATIONS
The process of genetic development within a fetus is an extremely delicate task on the body, and its to say nearly no human is genetically "perfect". Allergies and other such external symptoms may be related to a slight error made while the DNA was being developed, putting into perspective the likelihood of genetic disorders. Genetic mutations on the other hand, are larger issues within the genes [7].
Genetic mutations can widely vary, and there are many we as a scientific community have researched. Some are X-linked, but genetic mutations generally occur during cell division. Genetic mutations can affect chromosomes, with some like trisomy 18 (Edwards Syndrome) or turner syndrome being examples.
CONCLUSION
Chromosomes as a whole are a wide topic spanning all of human evolution, rising to new feats as we advance. Chromosomes are vital structures that package and protect DNA, ensuring accurate genetic inheritance and cellular function across generations. They bridge the gap between microscopic molecular coding and macroscopic biological diversity.
BIBLIOGRAPHY
1) "SRY Gene." MedlinePlus Clinic, medlineplus.gov/genetics/gene/sry/ . Accessed
8 Mar. 2026.
2)"Y Chromosome." MedlinePlus Clinic, medlineplus.gov/genetics/gene/sry/. Accessed
8 Mar. 2026.
3) "X Chromosome." MedlinePlus Clinic, medlineplus.gov/genetics/gene/sry/. Accessed
8 Mar. 2026.
4) Sun, Sheng, and Joseph Heitman. “Should Y stay or should Y go: the evolution of non-recombining sex chromosomes.” BioEssays : news and reviews in molecular, cellular and developmental biology vol. 34,11 (2012): 938-42. doi:10.1002/bies.201200064
5) Charlesworth, Deborah. “Evolution of recombination rates between sex chromosomes.” Philosophical transactions of the Royal Society of London. Series B, Biological sciences vol. 372,1736 (2017): 20160456. doi:10.1098/rstb.2016.0456
6) Soloman, Benjamin. "Lyonization." National Human Genome Research Institue, 8
Mar. 2026, www.genome.gov/genetics-glossary/Lyonization. Accessed 8 Mar.
2026.
7) "What is a genetic mutation?" Cleveland Clinic, https://my.clevelandclinic.org/health/body/23095-genetic-mutations-in-humans . Accessed
8 Mar. 2026
