Sex Determination and Development - Essay Example

Sex Determination and Development Introduction Cells are the building blocks that are basic in all types of living things that form the basis of organs. The cells are in trillions to compose a human body which are the basic foundation of body structure. These structures are essential in the intake of nutrients form food, special functions duty which are specialized and creates energy through the conversion of the nutrients. The body materials that are hereditary are also found in the human body cells and can duplicate themselves. Cells have numerous parts that have special and different function on each of them. (Yashon & Cummings, 2012) These parts that are known as organelles perform specific tasks and are structured within the cell. Human cell structure consists of cytoplasm, cytoskeleton, endoplasmic reticulum, Golgi apparatus, peroxisomes and Lysosomes, Nucleus, Mitochondria, Ribosome and Plasma membrane. Sex Development The nucleus in human body has 22 pairs of chromosomes, that belong to autosomes and a pair of sex chromosomes. This pair is always denoted as Y and X where a female contains two X-chromosomes while that of male contains an X and Y – chromosome. One of the X-chromosomes in a woman is activated in a form known as heterochromatin or sex chromatin and is the determinant of genetic gender on the basis of Barr body. The inactivation takes place in the stage known as blastocyst in a random manner on either X chromosome which may be material or paternal chromosome. In the presence of a Y- chromosome the development that takes place then is in the manhood form or masculine and in its absence the development occurs in feminism. What determine the gender is not gonosomes numbers but the absence or presence of Y-chromosome. The chromosome’s localized gene operates at its early stages in the development to be a guide known as a master gene in the Y chromosome in the determination of sex. (Chadwick & Goode, 2002) The Y- chromosome has a testis determining effect on gonads that are indifferent. This gene that is small is localized in the shorter arm and gets expressed in the supporting cells’ precursors. It then controls the entire number of genes found in the autosomes and on the X chromosomes. Sex determination in Mammals The sex development in mammals depends on the Y chromosomes. When there is existence of Y chromosomes then a male develops while in the absence of Y chromosomes then the resultant development is a female. The chromosomes for sexual dimorphic in a male are always two which are designated as Y and X while that of the female involves a pair of X chromosomes. A complete set of non-sex chromosomes is indicated by the use of A. Therefore the sperm produced by the male is indicated as AY and AX. The system results to the generation of a sex ratio or male offspring proportion at half if the XA and XY sperms are able to fertilize in an equal manner. This result is based on the provision of equally viable embryos known as AAYY and AAXX. (Bhattacharyya, 2012) In the context of same pair of chromosome then the resultant product is a female while in the case of different chromosomes then the expected result if a male products. Therefore the determination of the sex of the product is based on the connection and attachment of the chromosomes from both male and female. The strength of the male chromosomes visa vie that of the female plays important role in the sex determination in the mammals. Chromosome Number The changes in chromosome number are based in two types. It can be the change in the entire sets of chromosome that may result to a condition known as aberrant euploidy or changes in parts of the sets of chromosomes that will result to aneuploidy. In Aberrant Euploidy organisms that have multiples of the basic chromosomes set have diploid and haploid of normal euploidy. In this case, the polyploidy that have odd numbers of chromosome sets are highly infertile due to the aneuploidy of offspring and gametes. In comparison between the diploid and polyploidy plants, the polyploidy are usually larger and contain component parts that are larger than diploid. The synthesization of allopolyploid plants can be done through crossing of species that are related hence doubling the hybrid chromosomes. In order to create a new plant-line, monoploids are produced through geneticists through favorable genotypes hence chromosomes are doubled to form homozygous, fertile diploids. In Aneuploidy, the chromosome aberrations have abnormal number of chromosome. (Doltar, Mclean, Peterson, & Silber, 2013) Nondisjunction condition involves the production of aneuploid organisms through meiosis. The first meiosis Nondisjunction is very frequent than second meiosis. This indicates the crossovers necessity in the intact tetrad maintenance until the first anaphase. In gene balance, the increase in full chromosome set numbers usually correlate with organism size increase. However, the general proportion and size of the organism are usually the same as before. The genetic imbalance in aneuploidy has the tendency of being deleterious due to the difference in euploids genes ratio from and the difference interferes with the way gemone functions normally. Genes Generation in Sex Development DNA is different from all other biological molecules in the sense that it can replicate by itself through the help of specialized proteins. Each base strands can serve as a duplication template for the division of cell. The cellular units that form the basic components of the cell that can be inherited are the chromosome. The transformation and replication of the chromosomes can be observed by the scientist as they take place from cell to cell through microscope. (Somit & Peterson, 2012) DNA that is copies can be transmitted from a parent to a child beyond the cell to cell transmission through the sperm cell and egg. The DNA sequences that can be specified can be conserved from on species to the other which demonstrates how all living things are related. Therefore, besides variation, the responsibility of the continuity of genes is based on DNA. A child is in a position to inherit half of their DNA from that of the parent and each parent always passes half of their DNA to the child. This transmission is made possible through the process of sexual fertilization in which requires the meeting of the egg and the sperm. This results to the combination of both the egg and sperm DNA which is always composed of half genetic compositional information of the parent. This proves the genetic identity that is always maintained by many families despite the genetically differences that can be identified in the child that is not from the parent or from the related grandparents. (Finkel, 2012) This difference can also be identified from all the brothers and sisters unless in the condition of identical twins. Primary Sex Differentiation The differentiation starts to appear in the embryo of human as it develops. In the first six weeks of the gestation a difference can be realized in the gonad. The differentiation in the female sex is seen in the primordial germ cell which degenerate mesonephric tubule through the modularly code. This plays a vital role in the development of the ovary that is part of the female organ. The male differentiation can be detected through the paramesonephric duct which is also known as Mullerian duct. This development can be detected in its resemblance to the Mesonephric tubule and the Rete testis cords which form part of the development of the testis. (Christensen & Eyring, 2011) The Sry+ activity and the Y-linked gene play a vital role after the first stage of indifference. The Y-linked gene helps in production control and testis development during the cells differentiation hence the production of two key hormones which are known as the anti-Mullerian and testosterone hormone. Sex differentiation in the primary genes control of the male production involves active Sry+ and Sox-9+ genes plus an inactive Dax-1+ gene. This results to active Amh+ and inactive Wnt-4+ genes which give a secondary hormones controlling sex differentiation. This differentiation always has active testosterone and anti-Mullerian hormones. In the female production process, the active gene is Dax-1+ while the inactive gene is Sox-9+ which results to Wnt-4+ active gene and Amh+ inactive gene. This results to inactive gene that has no testosterone and anti-Mullerian hormone. Genital Development The primordial germ cells that are always surrounded by the gonadal epithelial cells that are proliferating immigrate to create a primitive sex cords. In the female genital duct human development takes place in the fourth gestation month. At this point, the Wolffian and Mullerian ducts are already in place. The Wolffian duct which is attached to the surface epithelium that forms the circular covering to the Oogonium and the Follicle cells develops to its fullness to become an Ovary. The Mullerian duct that goes across the Wolffian duct develops to its fullest to form the Uterus that attaches to the vagina. At Birth, an oviduct is formed from a proximal portion of the Mullerian duct. Moreover, the portions known as distal will have fused to the formation of upper vagina and uterus from the Mullerian duct. Therefore the duct has degenerated and cannot be detected in its original form as it was earlier. The development of the genital duct of the human male also happens in a different manner from that of the female. (Hedrick, 2011) It takes place in the fourth month of the gestation. This is when the Wolffian duct’s proximal portion becomes embedded in the kidney form embryo. The Rete testis develops to its full growth. The Mesonephric tubule develops to efferent tubules while testis cords and tunica albuginea develops to their full growth. The Wolffian duct develops to form the ductus deferens, seminal vesicle and ejaculatory duct. The Mullerian duct degenerates almost completely and its function is not detected. It becomes inactive in the male genital development but very active and develops in the female genital development. Reference Bhattacharyya, S. (2012). Magical Progeny, Modern Technology: A Hundu Bioethics of Assisted Reproductive Technology. New York: State University of New York Press. Chadwick, D., & Goode, J. (2002). The Genetics and Biology of Sex Determination. West Sussex: Novartis Foundation. Christensen, C. M., & Eyring, H. J. (2011). The Innovative University: Changing the DNA of Higher Education from the Inside Out. United States: John Wiley & Sons Publishers. Doltar, R., Mclean, K., Peterson, B., & Silber, K. (2013). Preparing for the AP Biology Examination. Boston: COURSE TECHNOLOGY CANGAGE Learning. Finkel, E. (2012). The Gemone Generation. Carlton: Melbourne University Press. Hedrick, P. W. (2011). Genetics of Populations. Canada: Jones and Bartlett Publishers. Somit, A., & Peterson, S. A. (2012). Biopolicy: The Life Sciences and Public Policy. United Kingdom: Emerald Group Publishing Limited. Yashon, R., & Cummings, M. (2012). Human Genetics and Society. Belmont: BROOKS/COLE CANGAGE Learning. Read More