A chromosome is a package of DNA with part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation.
Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology, that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. Techniques used include karyotyping, analysis of G-banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH).
In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal, and Robertsonian translocation. Reciprocal translocation is a chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two detached fragments of two different chromosomes are switched. Robertsonian translocation occurs when two non-homologous chromosomes get attached, meaning that given two healthy pairs of chromosomes, one of each pair "sticks" and blends together homogeneously.
Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling.
Medical genetics is the branch of medicine that involves the diagnosis and management of hereditary disorders. Medical genetics differs from human genetics in that human genetics is a field of scientific research that may or may not apply to medicine, while medical genetics refers to the application of genetics to medical care. For example, research on the causes and inheritance of genetic disorders would be considered within both human genetics and medical genetics, while the diagnosis, management, and counselling people with genetic disorders would be considered part of medical genetics.
Genetic analysis is the overall process of studying and researching in fields of science that involve genetics and molecular biology. There are a number of applications that are developed from this research, and these are also considered parts of the process. The base system of analysis revolves around general genetics. Basic studies include identification of genes and inherited disorders. This research has been conducted for centuries on both a large-scale physical observation basis and on a more microscopic scale. Genetic analysis can be used generally to describe methods both used in and resulting from the sciences of genetics and molecular biology, or to applications resulting from this research.
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or more individual chromosomes are altered. Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene. Chromosome anomalies usually occur when there is an error in cell division following meiosis or mitosis. Chromosome abnormalities may be detected or confirmed by comparing an individual's karyotype, or full set of chromosomes, to a typical karyotype for the species via genetic testing.
Molecular cytogenetics combines two disciplines, molecular biology and cytogenetics, and involves the analysis of chromosome structure to help distinguish normal and cancer-causing cells. Human cytogenetics began in 1956 when it was discovered that normal human cells contain 46 chromosomes. However, the first microscopic observations of chromosomes were reported by Arnold, Flemming, and Hansemann in the late 1800s. Their work was ignored for decades until the actual chromosome number in humans was discovered as 46. In 1879, Arnold examined sarcoma and carcinoma cells having very large nuclei. Today, the study of molecular cytogenetics can be useful in diagnosing and treating various malignancies such as hematological malignancies, brain tumors, and other precursors of cancer. The field is overall focused on studying the evolution of chromosomes, more specifically the number, structure, function, and origin of chromosome abnormalities. It includes a series of techniques referred to as fluorescence in situ hybridization, or FISH, in which DNA probes are labeled with different colored fluorescent tags to visualize one or more specific regions of the genome. Introduced in the 1980s, FISH uses probes with complementary base sequences to locate the presence or absence of the specific DNA regions. FISH can either be performed as a direct approach to metaphase chromosomes or interphase nuclei. Alternatively, an indirect approach can be taken in which the entire genome can be assessed for copy number changes using virtual karyotyping. Virtual karyotypes are generated from arrays made of thousands to millions of probes, and computational tools are used to recreate the genome in silico.
R. Ellen Magenis was an American pediatrician, medical geneticist and cytogeneticist.
David Owen Sillence is an academic and medical geneticist. He is an emeritus professor at the University of Sydney, where he was the foundation chair (Professor) of Medical Genetics. An honours graduate of the University of Sydney, he obtained his MD in Medical Genetics from the University of Melbourne 1978 in bone dysplasia.
Archana Sharma was a renowned Indian botanist, cytogeneticist, cell biologist, and cytotoxicologist. Her widely recognized contributions include the study of speciation in vegetatively reproducing plants, induction of cell division in adult nuclei, the cause of polyteny in differentiated tissues in plants, cytotaxonomy of flowering plants, and the effect of arsenic in water.
The International System for Human Cytogenomic Nomenclature is an international standard for human chromosome nomenclature, which includes band names, symbols, and abbreviated terms used in the description of human chromosome and chromosome abnormalities.
William Rees Brebner Robertson was an American zoologist and early cytogeneticist who discovered the chromosomal rearrangement named in his honour, Robertsonian translocation, the most common structural chromosomal abnormalities seen in humans that result in syndromes of multiple malformations, including trisomy 13 Patau syndrome and trisomy 21 Down syndrome.
Barbara Ruben Migeon was an American geneticist who was a professor at the Johns Hopkins University Institute of Genetic Medicine. She founded the Johns Hopkins program in Human Genetics and Molecular Biology. Migeon is the author of Females are Mosaics: X inactivation and sex differences in disease. She was awarded the American College of Medical Genetics and Genomics Dimes/Colonel Harland D. Sanders Lifetime Achievement Award in 2016.
Ernest Robert Sears was an American geneticist, botanist, pioneer of plant genetics, and leading expert on wheat cytogenetics. Sears and Sir Ralph Riley (1924–1999) are perhaps the two most important founders of chromosome engineering in plant breeding.
Lore Zech (1923—2013) was a German geneticist and cytogenetics researcher who made major contributions to the field of cytogenetics. Her research and discoveries paved the way for the identification of anomalies in chromosomes of diseased cells and eventually for many treatments and therapies for these diseases. Her notable works include her discovery of Q-banding and her research on leukemia and lymphoma.
The Human Genetics Society of Australasia (HGSA) is a membership organization for individuals in the field of human genetics who primarily practise in the Oceania region. Members typically hold both a qualification in human genetics and work in the field. Membership is drawn from clinical, laboratory and academic specialties. Members include clinical geneticists; genetic counsellors; laboratory scientists ; and academics.
Lyn Robyn Griffiths is an Australian academic who serves as Distinguished Professor of molecular genetics at Queensland University of Technology, where she is director of the Centre for Genomics and Personalised Health, the Genomics Research Centre and the BridgeTech Programs. Griffiths is internationally renowned for her work in the discovery of the genetics of migraine headaches.
