Von Recklinghausen's disease in mother, forme fruste type in son and daughter

Overview

Diploid organisms inherit genetic material through chromosomes from both parents. Copies of the same gene are known as alleles. In most cases, both alleles are simultaneously expressed and allow various cellular processes to function optimally. If one of the alleles is missing or mutated, the expression of the other allele can compensate; however, this is not true for all genes.
The expression of some genes depends on which parent passed the gene to the offspring, through a phenomenon known as...

The third stage of psychosexual development proposed by Freud is the phallic stage, occurring between the ages of 3 and 6. During this period, children become aware of their bodies and the differences between males and females. The erogenous zone in this stage is the genitals, and conflicts arise as children develop desires toward the opposite-sex parent. Boys experience the Oedipus complex, where they desire their mother and view their father as a rival. This leads to castration anxiety, the...

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

Gregor Mendel's work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid cell has two variants called alleles inherited from each parent. He suggested that amongst these two alleles, one allele is dominant in character and the other recessive. The combination of alleles determines the phenotype of a gene in an organism.

Most DNA resides in the nucleus of a cell. However, some organelles in the cell cytoplasm⁠—such as chloroplasts and mitochondria⁠—also have their own DNA. These organelles replicate their DNA independently of the nuclear DNA of the cell in which they reside. Non-nuclear inheritance describes the inheritance of genes from structures other than the nucleus.