NR nr507 midterm review

Epigenetics Epigenetics refers to heritable changes in gene expression that do not involve alterations to the DNA sequence itself. These changes, often referred to as “epigenetic modifications” or “tags,” include mechanisms such as DNA methylation and histone modification. These modifications can alter DNA accessibility and chromatin structure, which in turn regulates patterns of gene expression.

Histone Modifications Histone modifications are covalent post-translational changes to histone proteins, including processes such as methylation, phosphorylation, acetylation, ubiquitylation, and sumoylation. These modifications influence gene expression by altering chromatin structure or recruiting histone modifiers. Histone proteins play a crucial role in packaging DNA into chromosomes, with DNA wrapping around a core of eight histone proteins. Histone modifications are involved in various biological processes such as transcriptional activation/inactivation, chromosome packaging, and DNA repair. Quantitative detection of these histone modifications provides valuable insights into the regulation of cellular processes and the development of drugs targeting histone-modifying enzymes.

Prader-Willi Syndrome Prader-Willi syndrome (PWS) is a complex genetic disorder that affects multiple body systems. In infancy, it is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. As affected individuals reach childhood, they often develop an insatiable appetite, leading to chronic overeating (hyperphagia) and obesity. Additionally, some individuals with PWS, especially those with obesity, may develop type 2 diabetes, the most common form of diabetes.

Angelman Syndrome Angelman syndrome (AS) is a complex genetic disorder that primarily affects the nervous system. Key features of AS include delayed development, intellectual disability, severe speech impairment, and problems with movement and balance (ataxia). Many affected children also experience recurrent seizures (epilepsy) and a small head size (microcephaly). Delayed development is typically noticeable by the age of 6 to 12 months, with other symptoms becoming apparent in early childhood.

Prader-Willi Syndrome vs. Angelman Syndrome Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are distinct genetic disorders linked to abnormalities on chromosome 15q11-q13. Despite their shared chromosomal origin, they present with different clinical features. Both disorders exhibit unique neurological, developmental, and behavioral phenotypes along with other structural and functional abnormalities. Cognitive and neurological impairments are more severe in AS, including seizures and ataxia. Conversely, behavioral and endocrine disorders are more pronounced in PWS, including obsessive-compulsive symptoms and hypothalamic insufficiency. Both PWS and AS can result from microdeletion, uniparental disomy, or an imprinting center defect in the 15q11-q13 region. However, PWS is associated with abnormalities on the paternally derived chromosome 15, while AS is linked to the maternally derived chromosome 15 due to genomic imprinting. Although the same gene may regulate imprinting for both disorders, the genes responsible for their phenotypes differ. AS results from the underexpression of a single gene, UBE3A, which codes for the E6-associated protein.