Uniparental Disomy (UPD)

Review Cytogenetic contribution to uniparental disomy (UPD) Thomas  Liehr Jena University Hospital, Institute of Human Genetics and Anthropology, Kollegiengasse 10, D-07743 Jena, Germany Uniparental disomy (UPD) is often considered as an event to be characterized exclusively by molecular genetic or epigenetic approaches. This review shows that at least one third of UPD cases emerge in connection with…

Inheritance patterns

Inheritance patterns trace the transmission of genetically encoded traits, conditions or diseases to offspring.  There are several modes of inheritance: Single Gene or Mendelian Multifactorial Mitochondrial Note: These explanations use pedigrees to illustrate inheritance patterns.  If you are unfamiliar with pedigrees, see Pedigrees for an explanation of the symbols. Single Gene Inheritance Genetic conditions caused…

Autosomal recessive inheritance pattern

  To have an autosomal recessive disorder, you inherit two mutated genes, one from each parent. These disorders are usually passed on by two carriers. Their health is rarely affected, but they have one mutated gene (recessive gene) and one normal gene (dominant gene) for the condition. Two carriers have a 25 percent chance of…

Penetrance and expressivity

Classically, the genetic basis of the dependence of one gene on another is deduced from clear genetic ratios. However, only a small proportion of genes in the genome lend themselves to such analysis. One important property is that the mutation not exhibit decreased viability or fertility relative to wild type so that the frequency of…

PCR – principle, advantages and disadvantages

Developed in 1983 by Kary Mullis,[1] PCR is now a common and often indispensable technique used in medical and biological research labs for a variety of applications.[2][3] These include DNA cloning for sequencing, DNA-based phylogeny, or functional analysis of genes; the diagnosis of hereditary diseases; the identification of genetic fingerprints (used in forensic sciences and…

Restriction Enzymes

Restriction Enzymes Restriction enzymes are DNA-cutting enzymes found in bacteria (and harvested from them for use). Because they cut within the molecule, they are often called restriction endonucleases. In order to be able to sequence DNA, it is first necessary to cut it into smaller fragments. Many DNA-digesting enzymes (like those in your pancreatic fluid)…

X Chromosome: X Inactivation

By: Janice Y. Ahn (Harvard Medical School) & J. T. Lee, Ph.D. (Department of Genetics, Harvard Medical School) © 2008 Nature Education Females (XX) carry twice as many X-linked genes on their sex chromosomes as males (XY). How do cells control gene expression to manage this potentially lethal dosage problem? Figure 1: Tortoiseshell cat. The patchy distribution of color on tortoiseshell cats results from…

Genetics of Breast and Ovarian Cancer (PDQ®)

General Information  [Note: Many of the medical and scientific terms used in this summary are found in the NCI Dictionary of Genetics Terms. When a linked term is clicked, the definition will appear in a separate window.]  [Note: Many of the genes and conditions described in this summary are found in the Online Mendelian Inheritance…

Hereditary Breast and Ovarian Cancer

Having a family history of breast and ovarian cancer affects a woman’s risk for developing these diseases. Learn about hereditary risk, and whether you might benefit from cancer genetic counseling and testing. Know Your Family History All women should collect and record their family history of breast and ovarian cancer. Update your family history on…

Chromosomal translocations leading to activation of proto-oncogenes

In some cancerous cells; chromosomal translocations have been  discovered, where an oncogene of one chromosome is brought into the proximity  of an Ig locus on another chromosome (e.g. plasmacytomas in the mouse  and Burkitt lymphomas in man). Such translocations lead to activation of a  proto-oncogene like c-myc (Fig. 45.5), which is located on chromosome 8 …