Genetic Principles
Gail S. Anderson in Biological Influences on Criminal Behavior, 2019
Except for the sex chromosomes, a person always has two of each chromosome. With the sex chromosomes, females have two X chromosomes but males only have one. This means that the female can have one recessive gene that will not express itself because it will be protected or hidden by the dominant one. However, a male only has one X chromosome, so if he receives the recessive allele, there is not another allele to hide it, and it will be expressed. As a result, the recessive allele is expressed in the male, while the female is normally only a carrier. The female will only actually have the disease if she gets a recessive gene from each parent, which is rare. There are lots of such traits, not just disorders, that are seen more commonly in males than in females. Females who are carriers can pass recessive genes to their sons, who will express them, but their daughters will only be carriers, like their mothers.
Aneuploidy in Human Oocytes and Preimplantation Embryos
Carlos Simón, Carmen Rubio in Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
After 30 years of widely held belief that humans had 48 chromosomes, the refinement of karyotyping techniques in the 1950s facilitated the discovery that humans have 46 chromosomes, including the XY sex chromosomes (1). Using improved cytogenetic techniques, Jacobs and Strong (1959) reported that Klinefelter Syndrome in males was caused by an extra X chromosome (2). In the same year, Jejeune, Gauthier, and Turpin (3,4) and the Jacobs group (5) independently discovered that Down Syndrome was caused by an extra chromosome 21. Ford and colleagues (6) found that Turner Syndrome was caused by the loss of an X chromosome (45,X) in females and also reported the first mosaic individual (XXY/XX)(7). These studies reported in 1959 led to an explosion in the investigations into aneuploidy (8–12) and initiated epidemiological and extensive cohort studies of both spontaneous miscarriages as well as live births (Figure 8.1). Of spontaneous miscarriages, nearly 50% are chromosomally abnormal, mainly due to aneuploidy (one in three), but triploid conceptions are also common (13). To date, the most comprehensive cohort study is the US National Down Syndrome Project, which was initiated by Terry Hassold and Stephanie Sherman (14).
Endocrinology and diabetes
Shibley Rahman, Avinash Sharma in A Complete MRCP(UK) Parts 1 and 2 Written Examination Revision Guide, 2018
Common causes of primary hypogonadism include:Klinefelter’s syndrome. This condition results from a congenital abnormality of the sex chromosomes, X and Y. A male normally has one X and one Y chromosome. In Klinefelter’s syndrome, two or more X chromosomes are present in addition to one Y chromosome. The Y chromosome contains the genetic material that determines the sex of a child and related development. The extra X chromosome that occurs in Klinefelter syndrome causes abnormal development of the testicl*s, which in turn results in underproduction of testosterone.Mumps orchitis If a mumps infection involving the testicl*s in addition to the salivary glands (‘the mumps orchitis complex’) occurs during adolescence or adulthood, long-term testicular damage may occur. This may affect normal testicular function and testosterone production.haemochromatosisinjury to the testicl*streatment for cancerageing
Genetic polymorphisms of 17 X-STR loci in two Tunisian populations from Sousse and Makthar
Published in Annals of Human Biology, 2022
Abir Mejri, Miriam Baeta, Rim Al-Haj-Taib, Rene J. Herrera, Amel Benammar-Elgaaied, Marian M. de Pancorbo, Karima Fadhlaoui-Zid
The X-chromosome is one of the two chromosomes determining sex in humans. Females inherit one of their two X-chromosomes from their mother and the other from their father, while males receive only their X-chromosome from their mother. The forensic potential of this chromosome is mainly due to its inheritance pattern, as well as the easy access to its haplotypes. As a result, the interest in studying genetic markers located on the X-chromosome such as X-STRs has increased (Tillmar etal. 2017). This has resulted in the creation of X-STR typing panels (Diegoli 2015; Prieto-Fernández etal. 2016a). Due to their characteristics, X-chromosome markers, especially X-STRs, have gained recognition as powerful tools to complement the information provided by autosomal STRs and mitochondrial DNA. X-STRs are especially informative in kinship analyses where the majority of the profiles to compare correspond to second- or third-degree relatives, ie grandparents-grandchildren, paternal half-sisters, paternal aunt/uncle nieces and maternal uncle-nephews (Pinto etal. 2011).
Beyond the amyloid hypothesis: how current research implicates autoimmunity in Alzheimer’s disease pathogenesis
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Miyo K. Chatanaka, Dorsa Sohaei, Eleftherios P. Diamandis, Ioannis Prassas
The underlying causative factors that lead to autoimmunity remain elusive, and several hypotheses exist. Sex seems to play a pivotal role in autoimmunity risk. Women are more susceptible to autoimmune diseases by a factor of up to 16 [8]. This sexual dimorphism could be attributed to the sex chromosomes. Research suggests [9] that men with Klinefelter syndrome (genotype XXY) develop autoimmune diseases with the same frequency as women (genotype XX). Moreover, numerous genes on the X chromosome are related to immune function. Although one copy is usually deactivated, studies have shown that as many as 23% of X-linked genes escape this process, which could aggravate the immune response [10]. Interestingly, neurological disorders, such as Alzheimer’s disease (AD) and Multiple Sclerosis (MS) also display variable incidence according to sex [11]. Specifically, AD has a higher prevalence in women above 65 years old at a 1.6–3:1 ratio [12,13], and MS is more common in women by a ratio of 2–3:1 [14].
Greater male vulnerability to stunting? Evaluating sex differences in growth, pathways and biocultural mechanisms
Published in Annals of Human Biology, 2021
Amanda L. Thompson
These sex-based differences in sensitivity to maternal and environmental conditions have been attributed to the metabolic and immunological roles of sex chromosome-linked genes and sex hormones (Libert etal. 2010; Markle and Fish 2014; Giefing-Kröll etal. 2015; DiPietro and Voegtline 2017). Beginning prenatally, sex chromosome-linked genes differentially influence male and female development. The abundance of X-linked genes involved in placentogenesis may contribute to greater placental dysfunction and impaired growth in male foetuses (Pérez-Cerezales etal. 2018). The X chromosome also has numerous genes that are directly and indirectly linked to immune function (Markle and Fish 2014). The greater heterozygosity in these loci in females has been proposed to contribute to their stronger immune response to microbial infection (Libert etal. 2010).
Related Knowledge Centers
- Founder Effect
- Locust
- Sex Chromosome
- Y Chromosome
- Mitosis
- Xy Sex-Determination System
- Xo Sex-Determination System
- Meiosis
- Staining
- Base Pair
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