Chromosomes are thread-like structures found inside the nucleus of animal and plant cells. They are composed of DNA tightly coiled many times around proteins called histones, which support their structure. These structures carry our genetic information, organized into units called genes. Humans typically have 23 pairs of chromosomes, totaling 46.
One of these pairs is identified as chromosome 16. Each chromosome pair has a unique size and contains a distinct set of genes. Chromosome 16 plays a part in human development and function.
Understanding Chromosome 16
Chromosome 16 is one of the medium-sized human chromosomes, spanning approximately 90 million DNA base pairs. It is estimated to contain between 800 and 1,000 genes, which provide instructions for making various proteins. The proteins encoded by these genes participate in a broad range of biological processes, including cellular communication, metabolism, and the development of different body systems.
Health Conditions Linked to Chromosome 16
Alterations on chromosome 16 can lead to a range of health conditions. Rubinstein-Taybi syndrome, for example, is often associated with changes in the CREBBP gene located on chromosome 16. Individuals with this syndrome may experience broad thumbs and toes, intellectual disability, and distinctive facial features.
Another condition, 16p11.2 deletion/duplication syndrome, involves either the absence (deletion) or an extra copy (duplication) of a specific segment on the short arm of chromosome 16. Deletions in this region have been linked to developmental delays, intellectual disability, and an increased likelihood of autism spectrum disorder. Conversely, duplications of the same 16p11.2 segment have been associated with developmental delays, intellectual disability, and a lower body mass index.
Autosomal dominant polycystic kidney disease (ADPKD) is primarily caused by mutations in the PKD1 or PKD2 genes, both situated on chromosome 16. This condition leads to the growth of numerous fluid-filled cysts in the kidneys, which can impair kidney function over time.
How Chromosome 16 Variations are Inherited and Identified
Variations on chromosome 16 can be inherited from a parent or arise anew in an individual. Autosomal dominant inheritance means only one copy of an altered gene from either parent is sufficient to cause a condition. Autosomal recessive inheritance requires two altered copies, one from each parent, for the condition to manifest. Some variations, known as de novo mutations, occur spontaneously in an egg or sperm cell or early in embryonic development, meaning they are not inherited from either parent.
Genetic testing methods are used to identify these variations. Karyotyping examines the number and structure of an individual’s chromosomes. This test can detect large-scale changes, such as extra or missing chromosomes or significant structural rearrangements.
Chromosomal microarray analysis provides a more detailed view, capable of detecting smaller deletions or duplications of genetic material that karyotyping might miss. Exome sequencing focuses on the protein-coding regions of genes across the entire genome. This method can pinpoint specific gene mutations on chromosome 16 that may be responsible for a condition. These tests are performed for diagnosis, to assess risk in family planning, or during prenatal screening.