Autosomal Dominant Inheritance: Autosomal dominant inheritance follows a pattern where a single copy of a mutated gene from one parent is sufficient to cause the manifestation of a trait or disorder in the offspring. This means that if one parent carries the dominant allele, there's a 50% chance that each child will inherit the trait.
Huntington's Disease: It is caused by a mutation in the HTT gene, located on chromosome 4. Individuals with just one copy of the mutated gene will eventually develop the disease, usually in adulthood, leading to progressive cognitive and motor decline.
Neurofibromatosis Type 1: NF1 results from mutations in the NF1 gene, leading to the development of benign tumors along nerves throughout the body. Symptoms can vary widely, ranging from skin abnormalities to skeletal deformities and neurological complications.
Marfan Syndrome: Marfan syndrome, characterized by skeletal abnormalities, cardiovascular issues, and ocular complications, is caused by mutations in the FBN1 gene. This autosomal dominant disorder affects connective tissue, leading to a range of symptoms that can vary in severity among affected individuals.
Autosomal Recessive Inheritance: Autosomal recessive inheritance necessitates inheriting two copies of the mutated gene – one from each parent – for the trait or disorder to manifest. Carriers of the recessive allele typically do not display symptoms themselves but can pass on the mutated gene to their offspring.
Cystic Fibrosis: Cystic fibrosis (CF) is a life-limiting genetic disorder caused by mutations in the CFTR gene. Inheritance follows an autosomal recessive pattern, meaning that individuals must inherit two faulty copies of the gene to develop the disease. CF affects the lungs, pancreas, and other organs, leading to respiratory infections, digestive issues, and impaired growth.
Sickle Cell Anemia: Sickle cell anemia, a hereditary blood disorder, results from mutations in the HBB gene, leading to the production of abnormal hemoglobin molecules. Individuals with two copies of the mutated gene experience red blood cells that become rigid and sickle-shaped, causing episodes of pain, anemia, and increased susceptibility to infections.
Phenylketonuria (PKU): Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by mutations in the PAH gene. It leads to the inability to metabolize the amino acid phenylalanine, resulting in its accumulation in the body and causing intellectual disabilities and other neurological problems if left untreated.
X-linked Inheritance: X-linked inheritance involves genes located on the X chromosome, and the inheritance pattern differs between males and females due to sex chromosome composition. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). X-linked recessive disorders are more common in males, as they have only one X chromosome.
Hemophilia: Hemophilia is a classic example of an X-linked recessive disorder, characterized by impaired blood clotting due to deficiencies in clotting factors VIII (hemophilia A) or IX (hemophilia B). Since males have only one X chromosome, inheriting a single mutated copy of the gene from their mother results in the manifestation of the disorder.
Color Blindness: Color blindness, specifically red-green color blindness, is another X-linked recessive condition. It affects the ability to perceive certain colors and is more prevalent in males. Females can be carriers of the gene without displaying symptoms, but if they have a son with a male partner who carries the gene, there's a chance of passing on the disorder.
Fragile X syndrome: X-linked dominant disorders result from changes in genes located on the X chromosome. In males, who possess only one X chromosome, a mutation in the single copy of the gene, leads to the disorder. Females, with two X chromosomes, require a mutation in only one of the two copies of the gene to manifest the disorder. Symptoms in females might be milder compared to males. Notably, X-linked traits cannot be passed from fathers to sons (no transmission from male to male) in X-linked inheritance. Changes in the FMR1 gene result in fragile X syndrome. This gene is responsible for encoding the protein known as FMRP. This protein assists in controlling the synthesis of other proteins and contributes to the formation of synapses during development.
Y-linked Inheritance: Since only males possess a Y chromosome, inheritance in Y-linked conditions occurs exclusively from father to son. An example of this is Y chromosome infertility.
Co-Dominant Inheritance: Codominant inheritance occurs when two distinct versions or alleles of a gene are both expressed, resulting in the production of slightly different proteins. Each allele contributes to the genetic trait or determines the characteristics of the genetic condition. An example of this is the ABO blood group.
Mitochondrial Inheritance: Also known as Maternal inheritance, it pertains to genes located in mitochondrial DNA. Mitochondria, organelles responsible for converting molecules into energy within cells, contain a small portion of DNA. Since only egg cells provide mitochondria to the developing embryo, mitochondrial variants can only be transmitted by females to their offspring. Disorders arising from mutations in mitochondrial DNA can manifest in every generation of a family and can affect both males and females. However, fathers do not transmit these disorders to their sons or daughters. An example of this Leber hereditary optic neuropathy (LHON).
-Written by Sohni Tagore