Human genome

genomehuman DNAhuman geneticist
Since then hundreds of personal genome sequences have been released, including those of Desmond Tutu, and of a Paleo-Eskimo. In November 2013, a Spanish family made their personal genomics data publicly available under a Creative Commons public domain license. The work was led by Manuel Corpas and the data obtained by direct-to-consumer genetic testing with 23andMe and the Beijing Genomics Institute). This is believed to be the first such public genomics dataset for a whole family. The sequencing of individual genomes further unveiled levels of genetic complexity that had not been appreciated before.


deoxyribonucleic aciddouble-stranded DNAdsDNA
DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the sequence of pieces of DNA called genes. Transmission of genetic information in genes is achieved via complementary base pairing. For example, in transcription, when a cell uses the information in a gene, the DNA sequence is copied into a complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides.

Genetic genealogy

Geneticgenetic genealogistgenetic genealogists
Later, GeneTree returned to genetic testing for genealogy in conjunction with the Sorenson parent company and eventually was part of the assets acquired in the buyout of SMGF. In 2000, Family Tree DNA, founded by Bennett Greenspan and Max Blankfeld, was the first company dedicated to direct-to-consumer testing for genealogy research. They initially offered eleven marker Y-Chromosome STR tests and HVR1 mitochondrial DNA tests. They originally tested in partnership with the University of Arizona. In 2007, 23andMe was the first company to offer a saliva-based direct-to-consumer genetic testing.

Whole genome sequencing

genome sequencingsequencedfull genome sequencing
This potential use of genome sequencing is highly controversial, as it runs counter to established ethical norms for predictive genetic testing of asymptomatic minors that have been well established in the fields of medical genetics and genetic counseling. The traditional guidelines for genetic testing have been developed over the course of several decades since it first became possible to test for genetic markers associated with disease, prior to the advent of cost-effective, comprehensive genetic screening.


mutationsgenetic mutationmutated
Chromosomal translocations: interchange of genetic parts from nonhomologous chromosomes. Chromosomal inversions: reversing the orientation of a chromosomal segment. Non-homologous chromosomal crossover. Interstitial deletions: an intra-chromosomal deletion that removes a segment of DNA from a single chromosome, thereby apposing previously distant genes. For example, cells isolated from a human astrocytoma, a type of brain tumor, were found to have a chromosomal deletion removing sequences between the Fused in Glioblastoma (FIG) gene and the receptor tyrosine kinase (ROS), producing a fusion protein (FIG-ROS).


Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a child's parentage (genetic mother and father) or in general a person's ancestry. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. Genetic testing identifies changes in chromosomes, genes, or proteins. Most of the time, testing is used to find changes that are associated with inherited disorders.


genesnumber of genesgene sequence
In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins, telomeres and the centromere. Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequence that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication. The length of the telomeres decreases each time the genome is replicated and has been implicated in the aging process.

Genealogical DNA test

DNA testDNA testinggenealogical DNA testing
List of DNA tested mummies. MyHeritage. 23andMe.


The gain or loss of an entire chromosome can occur through errors in mitosis. More common are mutations, which are changes in the nucleotide sequence of genomic DNA. Large-scale mutations involve the deletion or gain of a portion of a chromosome. Genomic amplification occurs when a cell gains copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material. Translocation occurs when two separate chromosomal regions become abnormally fused, often at a characteristic location.


genomesgenetic materialgenomic
Archaea have a single circular chromosome. Most bacteria also have a single circular chromosome; however, some bacterial species have linear chromosomes or multiple chromosomes. If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, and if the cells divide faster than the DNA can be replicated, multiple replication of the chromosome is initiated before the division occurs, allowing daughter cells to inherit complete genomes and already partially replicated chromosomes. Most prokaryotes have very little repetitive DNA in their genomes. However, some symbiotic bacteria (e.g.

Personalized medicine

personalised medicinetheranosticstheranostic
Genotyping is the process of obtaining an individual’s DNA sequence by using biological assays. By having a detailed account of an individual’s DNA sequence, their genome can then be compared to a reference genome, like that of the Human Genome Project, to assess the existing genetic variations that can account for possible diseases. A number of private companies, such as 23andMe, Navigenics, and Illumina, have created Direct-to-Consumer genome sequencing accessible to the public. Having this information from individuals can then be applied to effectively treat them.

Genetic disorder

genetic diseasegenetic disordersgenetic diseases
The sons of a man with an X-linked dominant disorder will all be unaffected (since they receive their father's Y chromosome), and his daughters will all inherit the condition. A woman with an X-linked dominant disorder has a 50% chance of having an affected fetus with each pregnancy, although in cases such as incontinentia pigmenti, only female offspring are generally viable. In addition, although these conditions do not alter fertility per se, individuals with Rett syndrome or Aicardi syndrome rarely reproduce. X-linked recessive conditions are also caused by mutations in genes on the X chromosome.

Mitochondrial DNA

mtDNAmitochondrialmitochondrial genome
(Y-chromosomal DNA, paternally inherited, is used in an analogous way to determine the patrilineal history.) This is usually accomplished on human mitochondrial DNA by sequencing the hypervariable control regions (HVR1 or HVR2), and sometimes the complete molecule of the mitochondrial DNA, as a genealogical DNA test. HVR1, for example, consists of about 440 base pairs. These 440 base pairs are compared to the same regions of other individuals (either specific people or subjects in a database) to determine maternal lineage. Most often, the comparison is made with the revised Cambridge Reference Sequence.

Elective genetic and genomic testing

Genetic testing for a variety of disorders has seen many advances starting with cytogenetics to evaluate human chromosomes for aneuploidy and other chromosome abnormalities. The development of molecular cytogenetics involving techniques such as fluorescence in situ hybridization (FISH) followed, permitting the detection of more subtle changes in the karyotype. Techniques to determine the precise sequence of nucleotides in DNA by DNA sequencing, notably Sanger sequencing was developed in the 1970s.

Family Tree DNA

Genealogical DNA test. Genetic genealogy. Human mitochondrial genetics. Phylogenetic tree. Short tandem repeat. Single-nucleotide polymorphism. Test types. DNA microarray. DNA sequencing. Polymerase chain reaction. Sanger sequencing. Test manufactures. Affymetrix. Applied Biosystems. Illumina. Genetic genealogy and anthro-genetics companies. 23andMe. deCODEme. GeneTree. Genographic Project. International Society of Genetic Genealogy (ISOGG). Sorenson Molecular Genealogy Foundation (SMGF).


The sequence of bases along a particular DNA molecule specifies the genetic information: this is comparable to a sequence of letters spelling out a passage of text. Before a cell divides through mitosis, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. A portion of a DNA molecule that specifies a single functional unit is called a gene; different genes have different sequences of bases. Within cells, the long strands of DNA form condensed structures called chromosomes. Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique combination of DNA sequences that code for genes.


Nucleic acid sequence. Phenotype. Potentiality and actuality. Quaternary numeral system. Sequence (biology).


The repair does not, however, always restore the original sequence. In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations. Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt a mistaken alignment; this makes some regions in genomes more prone to mutating in this way. These errors create large structural changes in DNA sequence – duplications, inversions, deletions of entire regions – or the accidental exchange of whole parts of sequences between different chromosomes (chromosomal translocation).

James Watson

WatsonJames D. WatsonJames Dewey Watson
Watson has repeatedly supported genetic screening and genetic engineering in public lectures and interviews, arguing that stupidity is a disease and the "really stupid" bottom 10% of people should be cured. He has also suggested that beauty could be genetically engineered, saying in 2003, "People say it would be terrible if we made all girls pretty. I think it would be great." In 2007, James Watson became the second person to publish his fully sequenced genome online, after it was presented to him on May 31, 2007, by 454 Life Sciences Corporation in collaboration with scientists at the Human Genome Sequencing Center, Baylor College of Medicine.


Genealogical DNA test. List of genetic genealogy topics. List of haplogroups of notable people. Indian maternal gene pool, Journal of Human Genetics''. Dienekes' Anthropology Blog frequent highlights of new results. Y Chromosome Consortium. ISOGG Y-DNA Haplogroup Tree. PhyloTree's Y-tree A minimal reference phylogeny for the human Y-chromosome. Haplogroup Predictor. The Y Chromosome Consortium (2002), A Nomenclature System for the Tree of Human Y-Chromosomal Binary Haplogroups, Genome Research, Vol. 12(2), 339–48, February 2002. (Detailed hierarchical chart has conversions from previous naming schemes).

Gaucher's disease

gaucher diseaseGaucherGaucher’s disease
Genetic counseling and genetic testing are recommended for families who may be carriers of mutations. Each type has been linked to particular mutations. In all, about 80 known GBA gene mutations are grouped into three main types: The Gaucher-causing mutations may have entered the Ashkenazi Jewish gene pool in the early Middle Ages (48-55 generations ago). Gaucher disease is suggested based on the overall clinical picture. Initial laboratory testing may include enzyme testing. As a result, lower than 15% of mean normal activity is considered to be diagnostic. Decreased enzyme levels will often be confirmed by genetic testing.

Medical genetics

medical geneticistclinical geneticsgenomic medicine
Chromosome analysis using a karyotype involves special stains that generate light and dark bands, allowing identification of each chromosome under a microscope. Fluorescence in situ hybridization (FISH) involves fluorescent labeling of probes that bind to specific DNA sequences, used for identifying aneuploidy, genomic deletions or duplications, characterizing chromosomal translocations and determining the origin of ring chromosomes. Chromosome painting is a technique that uses fluorescent probes specific for each chromosome to differentially label each chromosome. This technique is more often used in cancer cytogenetics, where complex chromosome rearrangements can occur.

Nucleic acid hybridization

In another technique, short DNA sequences are hybridized to cellular mRNAs to identify expressed genes. Pharmaceutical drug companies are exploring the use of antisense RNA to bind to undesired mRNA, preventing the ribosome from translating the mRNA into protein. Fluorescence in situ hybridization (FISH) is a laboratory method used to detect and locate a DNA sequence, often on a particular chromosome. Researchers Joseph Gall and Mary Lou Pardue realized in the 1960s that molecular hybridization could be used to identify the position of DNA sequences in situ (i.e., in their natural positions within a chromosome).

Exome sequencing

whole exome sequencingexomewhole-exome sequencing
Furthermore, because severe disease-causing variants are much more likely (but by no means exclusively) to be in the protein coding sequence, focusing on this 1% costs far less than whole genome sequencing but still detects a high yield of relevant variants. In the past, clinical genetic tests were chosen based on the clinical presentation of the patient (i.e. focused on one gene or a small number known to be associated with a particular syndrome), or surveyed only certain types of variation (e.g. comparative genomic hybridization) but provided definitive genetic diagnoses in fewer than half of all patients.

Outline of genetics

DNA sequencing. dominant. double helix. duplication. electrophoresis. fibroblasts. fluorescence in situ hybridization (FISH). gene. gene amplification. gene expression. gene library. gene mapping. gene pool. gene therapy. gene transfer. genetic code. ATGC. genetic counseling. genetic linkage. genetic map. genetic marker. genetic screening. genome. genotype. germ line. haploid. haploinsufficiency. hematopoietic stem cell. heterozygous. highly conserved sequence. holoprosencephaly. homologous recombination. homozygous. human artificial chromosome (HAC).