Genetic Disorders or Syndromes: Down syndrome, Turner syndrome, Phenylketonuria (PKU), and, Klinefelter Syndrome For Class 11th, and 12th  

Genetic Disorders or Syndromes: Down syndrome, Turner syndrome, Phenylketonuria (PKU), and, Klinefelter Syndrome For Class 11th, and 12th  


The genes of the parents can sometimes be passed on to the genes of the offspring, making genetic illnesses hereditary. Defects in the DNA or chromosomes of certain people with genetic illnesses may be the result of recent mutations. Some types of cancer, or specific cases of them, may be brought on by inherited genetic conditions in some people, new mutations in other people, and primarily environmental factors in some other people. Whether, when, and how much a person with a genetic condition or syndrome will experience the disease depends nearly always on several environmental circumstances and events that occur during the person’s development.

Some of the most prevalent genetic syndromes include  Down syndrome, Severe Combined Immunodeficiency Disorder (SCID), Jackson-Weiss Syndrome, Huntington’s disease, Sickle-cell disease, Turner syndrome, Phenylketonuria (PKU), Klinefelter Syndrome, etc

Klinefelter Syndrome

Dr Harry Klinefelter and his colleagues originally identified the set of characteristics that has come to be known as Klinefelter Syndrome in 1942. By the late 1950s, scientists had found that men who experienced this set of symptoms possessed an additional sex chromosome, XXY, rather than the typical male configuration of XY. Even while XXY is frequent, the condition is not prevalent. Many guys go through life never even realizing that they have an extra chromosome. Due to this, the name “Klinefelter syndrome” is no longer widely used in the medical field. Instead, many professionals prefer to refer to guys with an additional chromosome as “XXY males.”

Carriers of DNA, the genetic material, are chromosomes. Both sexes typically have two sex chromosomes. One X chromosome is inherited by a woman from each parent. Men receive their mother’s X chromosome and their father’s Y chromosome as inheritances.


Only males are diagnosed with Klinefelter’s syndrome, which is brought on by an extra X chromosome. Nobody is aware of what increases a couple’s chance of having an XXY child. Meiosis is a biological process that involves an accident that results in XXY. All cells that will develop into an egg or sperm go through meiosis. Chromosomes couple together and trade genetic material before meiosis is finished. The X chromosomes from each parent make a pair in females. Men have a pair of X chromosomes from their mother and Y chromosomes from their father. The chromosomes split after the exchange, and meiosis continues. The X and Y chromosomes or the two X chromosomes can sometimes fail to pair and share genetic material. An XXY man is created when a sperm with both X and Y chromosomes fertilizes an egg with just one X chromosome or when a regular sperm with a Y chromosome fertilizes an egg with two X chromosomes.


A kid with XXY may be slightly more likely to be born to older mothers. However, research has revealed that the extra chromosome typically originates from the mother 50% of the time and the father 50% of the time. Over 3,000 males are affected each year in the US, where it affects 1 in 500–1000 male births. All races are equally impacted. The mortality rate is not appreciably higher than it is in healthy people.

Clinical Symptoms

Symptoms’ severity might vary and can include:

Small penis and testicles; less facial, body, and pubic hair; and a higher-than-average height Long legs and arms – An increase in breast size (gynecomastia) – A lack of sperm production – Learning disorders, particularly language issues – A personality disorder


There is no cure for infertility brought on by this disease.

Down syndrome

The existence of a third copy of a chromosome, in whole or in part, results in the genetic condition known as Down syndrome. Physical growth delays, distinctive facial traits, and mild to severe intellectual handicaps are frequently connected with it. Every cell in the human body has a nucleus, which houses the genes that store genetic material. All of our inherited qualities are encoded by genes, which are arranged along rod-like structures called chromosomes. Each cell typically has 23 pairs of chromosomes in its nucleus, half of which are inherited from each parent. When chromosome 21 is fully or partially duplicated, Down syndrome is present. The development is altered by the extra genetic material, which also causes the Down syndrome-related traits.

Cystic fibrosis (CF)

With nearly 10 million people or one in every 31 Americans, harbouring the faulty gene, cystic fibrosis (CF) is the most prevalent genetic illness among Caucasians. 30,000 people in the United States are affected by this autosomal recessive disease, with half of those affected being 18 years of age or older. The disease is brought on by a mutation on chromosome 7 that alters the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Fertility and Reproductive Health Implications of Targeted Therapeutics for Cystic Fibrosis was described in detail by Ladores S.

Turner syndrome

Turner syndrome is a chromosomal disease in which a woman only has one healthy X chromosome. Other cell lines that include the Y chromosome or a portion of it, in addition to the X chromosome monosomy, can co-exist. A higher probability of gonadoblastoma development (15–30%) exists in Turner syndrome patients who have Y chromosomes. Turner Syndrome (TS) is listed as having karyotype 45 in an article by Susana Fernandes MSW of the United States titled “Y-Chromosome Detection in Turner Syndrome.” X is one of the most prevalent cytogenetic abnormalities (1:2500 among newborn females). Even though the vast majority of conceptuses with karyotype 45, X spontaneously perish, typically before 28 weeks of gestation, it is still possible for life to exist. More than 99 percent.

Phenylketonuria (PKU)

The primary enzyme in the catabolic pathway for phenylalanine, phenylalanine hydroxylase, is genetically predisposed to the condition. causes the blood’s phenylalanine levels to rise (Hyperphenylalaninemia). Phenylalanine or its metabolites accumulate in the body early in childhood and prevent the brain from developing normally, which results in severe intellectual deficiencies. This could be due to an imbalance of necessary metabolites brought on by too much phenylalanine competing with other amino acids for transport through the blood-brain barrier. The hydroxylation of a substrate by an O2 atom and the reduction of the other oxygen atom to H2O are both carried out simultaneously by this enzyme, which is classified as a mixed-function oxidase. The cofactor tetrahydrobiopterin, which transports electrons from NADPH to O2 and is subsequently oxidized to dihydrobiopterin, is needed by the enzyme phenylalanine hydroxylase. The enzyme dihydrobiopterin reductase then reduces it in a process that needs NADPH. A supplementary pathway of phenylalanine metabolism is active in people with PKU. In this route, phenylalanine is transaminated with pyruvate to produce phenylpyruvate. The condition is known as “phenylketonuria” because phenylalanine and phenylpyruvate build up in the blood and tissues and are eliminated in the urine. It is possible to catabolize phenylpyruvate to produce phenylacetate and phenyllactate. Nurses have always used the unique odour that phenylacetate gives the urine to identify PKU in neonates.

Diet of PKU patients: only enough phenylalanine and tyrosine must be consumed to support protein synthesis. Protein-rich foods must be consumed in moderation. Aspartame, an artificial sweetener, is a dipeptide made up of phenylalanine’s methyl ester and aspartate. Therefore, PKU sufferers should avoid it. Defects in the enzyme that catalyzes the regeneration of the cofactor tetrahydrobiopterin can also result in phenylketonuria. Treatment for this condition entails more than just limiting phenylalanine and tyrosine intake. Tetrahydrobiopterin is also necessary for the synthesis of L-3,4-dihydroxyphenylalanine (L-dopa), a precursor of the neurotransmitters norepinephrine and serotonin, and 5-hydroxytryptophan. Therefore, in phenylketonuria of this type, the diet must contain these precursors. Tetrahydrobiopterin itself cannot cross the blood-brain barrier and is unstable, making it ineffectual as a dietary supplement.


This hereditary condition results from a homogentisate dioxygenase enzyme deficiency. Homogentisate is expelled in large quantities, and when it oxidizes, it turns the urine black. A type of arthritis is also more likely to appear in those with alkaptonuria. The first person to tie an inherited characteristic with an enzyme was Archibald Garrod.

Phenylketonuria (commonly known as PKU) An genetic condition called phenylketonuria, or PKU, causes the blood to contain more of the amino acid phenylalanine. A necessary amino acid, phenylalanine is a dietary source of protein building blocks. Additionally, certain artificial sweeteners and all proteins include it. If PKU is left untreated, the body may accumulate dangerous levels of phenylalanine, which may lead to intellectual impairment and other major health issues.

Huntington’s disease

HD is a hereditary autosomal-dominant progressive neurodegenerative illness that typically shows up in adulthood. The phenotypes of the illness are unusual, with clear motor impairments, mental symptoms, and cognitive deterioration. Chorea (bizarre dance-like movements), dyskinesia (difficulty or distortion performing voluntary motions), and dystonia are some of the motor symptoms (involuntary contraction of muscles). Psychiatric symptoms like sadness, anxiety, and sleep problems typically appear before motor symptoms do (Spires and Hannan 2007). The cognitive decline shows itself as problems paying attention and remembering new information, a decline in language abilities, slurred speech, and perceptual deficits. As the illness worsens, dementia and motor stiffness become more prominent. Multiple brain regions exhibit neuropathology in HD, with the caudate nucleus and putamen experiencing the most deterioration (Vonsattel et al. 1985).

The Huntington’s Disease Collaborative Research Group (1993) described the mutation in the huntingtin (htt) gene as an unstable expansion of CAG (the trinucleotide code for glutamine) repeats that occurs within the first exon of the gene ‘IT 15’ (for ‘Interesting Transcript 15’) in HD patients. Huntingtin is a protein that is encoded by the gene on chromosome 4 (4p63). One of the most significant moments in the history of HD and genetics was the identification of mutant htt. It sparked a cascade of activities that included the rapid molecular diagnosis of HD and the creation of mutant htt knock-in transgenic disease models.

The huntingtin gene mutation results in an extended length of the amino acid glutamine (represented by the letter Q) towards the protein’s amino-terminal end. This alters the function of the mutant protein by causing aberrant interactions between it and other cellular proteins. With 8 to 36 glutamine repetitions in the general population and 41 or more in HD, the glutamine tract in the htt is polymorphic. People with 38 or more glutamine repeats in their HTT can develop HD, although it has also been observed that some elderly people with up to 41 repeats have HD without any obvious symptoms (Rubinsztein et al. 1996).

Jackson-Weiss syndrome

Jackson-Weiss syndrome is a hereditary condition that causes deformed feet and the early fusion of some cranial bones (craniosynostosis). This early fusion alters the shape of the head and face and stops the skull from developing normally. The early fusing of the skull bones is the cause of many of the distinctive facial traits associated with Jackson-Weiss syndrome. These bones grow abnormally, resulting in a malformed skull, widely spaced eyes, and a protruding forehead. The most recurring symptoms of Jackson-Weiss syndrome are deformed feet. Short and wide, and bending away from the other toes, the first (big) toes are the largest. Additionally, some toes may have bones that are improperly formed or fused (syndactyly). The hands are typically in a normal state. Hearing impairment is present in certain Jackson-Weiss syndrome patients. Most people with Jackson-Weiss syndrome are intelligent and live regular lives.

Haemophilia Hemophilia is a rare type of bleeding disorder caused by an inability or lack of a certain protein (clotting factor), which is required for blood to clot. Because the blood clot that forms is ineffective at stopping the bleeding, haemophiliacs experience more prolonged bleeding following an injury.

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