Human Genetics

Information about Human Genetics

Enlarge picture
A karyotype of a human male, showing 46 chromosomes including XY sex chromosomes.


Human genetics describes the study of inheritance as it occurs in human beings. This article describes only basic features of human genetics; for the genetics of disorders please see: Medical genetics.

Chromosomes

Humans have 46 chromosomes, arranged in 23 pairs (i.e. they are diploid). 44 (22 pairs) of these chromosomes are autosomes, and 2 (1 pair) are sex chromosomes. Humans have an XY sex determination system, so that females have the sex chromosomes XX and the males XY. The Y chromosome is shorter than the X chromosome, so that males are hemizygous over this region. X-linked recessive genes are thus expressed more often in males. A Humans' gender is determined by the x and the y chromosomes.

Number of genes

Estimates of the number of genes humans have has been possible since DNA sequencing was first introduced. Estimates however have varied wildly, though the present best guess is 20,000-25,000, estimates of up to 40,000 have been in the past.

Mitochondrial DNA

In addition to nuclear DNA, humans (like almost all eukaryotes) have mitochondrial DNA. Mitochondria, the "power houses" of a cell, have their own DNA because they are descended from a proteobacterium that merged with eukaryotic cells over 2 billion years ago. Mitochondria are inherited from one's mother, and its DNA is frequently used to trace maternal lines of descent (see mitochondrial Eve).

Genes and human characteristics

Genes have both minor and major effects on human characteristics. Human genes have become prominent in the nature versus nurture debate.

Genes and behavior

Genes have a strong influence on human behavior. IQ is largely heritable. However, this has been questioned. The stance that humans inherit substantial behavioral characteristics is called psychological nativism, compared to the stance that human behavior and culture are virtually entirely constructed (tabula rasa).

In the early 20th century, eugenics was policy in parts of the United States and Europe. The goal was to reduce or eliminate people whose genes were considered inferior. One form of eugenics was compulsory sterilization of people deemed mentally unfit. Hitler's eugenics programs turned social consciousness against the practice, and psychological nativism became associated with racism and sexism.

Genes and gender

The biggest genetic difference among healthy humans is in gender. Scientists debate the extent to which genes and culture affect gender roles. The case of David Reimer was once a case in point for the tabula rasa camp, though recently that same case has become evidence for a strong genetic component to gender identity.

Genes and race

Most genetic diversity occurs within races rather than between them. Common concepts of racial categories do not accurately match genetic characteristics.

Evolutionary psychology

Evolutionary psychology explains many human behaviors as more or less moderated by genes that evolved in the hunter-gatherer stage of human cultural development. See for example Stockholm syndrome.

Genetic disorders

Main article: Genetic disorder
Humans have several genetic diseases, often caused by recessive genes. See List of genetic disorders. Genetic disorders happen everywhere and are very common in some places.

Human traits with simple inheritance patterns

Dominant Recessive References
Widow's PeakNo Widow's Peak[1][2]
Facial DimplesNo Facial Dimples[3][4]
Able to taste PTCUnable to taste PTC[5]
Unattached earlobeAttached earlobe[3][6][7]
Cleft chinNo Cleft chin[8]
FrecklesNo Freckles[3][9]
Wet-type earwaxDry-type earwax[6][10]

See also

Human mitochondrial DNA (mtDNA) haplogroups
 most recent common mt-ancestor  
L0 L1 
L2L3 L4L5L6L7
 MN 
CZDEGQ AIO R SWXY
CZBFpre-HV pre-JTP UK
HVJTUK
HVJT

Human Y-chromosome DNA (Y-DNA) haplogroups
Y-most recent common ancestor
|
ABR
BCR
CDEF
DEGHIJK
IJLMNOP
NOQR

References

1. ^ Campbell, Neil; Jane Reece (2005). Biology. San Francisco: Benjamin Cummings, pp. 265. 
2. ^ Online Mendelian Inheritance in Man, ID=194000 [1]
3. ^ [2]
4. ^ Online Mendelian Inheritance in Man, ID=126100 [3]
5. ^ [4]
6. ^ Cruz-Gonzalez L., Lisker R. (1982). "Inheritance of ear wax types, ear lobe attachment and tongue rolling ability.". Acta Anthropogenet. 6 (4): 247-54. PMID 7187238. 
7. ^ Online Mendelian Inheritance in Man, ID=128900 [5]
8. ^ Online Mendelian Inheritance in Man, ID=119000 [6]
9. ^ Xue-Jun Zhang et al. "A Gene for Freckles Maps to Chromosome 4q32–q34" Journal of Investigative Dermatology (2004) 122, 286–290 [7]
10. ^ Online Mendelian Inheritance in Man, ID=117800 [8]

External links

 •  • [ e]
Human topics
 •  • [ e]
Human genetics
Human evolutionary genetics Human genetic engineering Human genetic history Human genetic variation Human genome Human evolution
 •  • [ e]
Human chromosomes
{1} {2} {3} {4} {5} {6} {7} {8} {9} {10} {11} {12} {13} {14} {15} {16} {17} {18} {19} {20} {21} {22} {X} {Y}
Medical Genetics is the application of genetics to medicine. Medical genetics is a broad and varied field. It encompasses many different individual fields, including clinical genetics, biochemical genetics, cytogenetics, molecular genetics, the genetics of common diseases (such as
..... Click the link for more information.
Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.
An autosome is a non-sex chromosome. It is an ordinarily pairedIn the case of higher ploidy levels than the usual diploid, there will be the same number of an autosome as the ploidy level itself. For example, in a pentaploid, there will be five copies of each autosome.
..... Click the link for more information.
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that
..... Click the link for more information.
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila) and some plants (Ginkgo). In the XY sex-determination system, females have two of the same kind of sex chromosome (XX), and are called
..... Click the link for more information.
Female (♀) is the sex of an organism, or a part of an organism, which produces ova (egg cells). The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon is produced by the male.
..... Click the link for more information.
Male (♂) refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilisation.
..... Click the link for more information.
Zygosity refers to the genetic condition of a zygote. In genetics, zygosity describes the similarity or dissimilarity of DNA between homologous chromosomes at a specific allelic position or gene.

Every gene in a diploid organism has two alleles at the gene's locus.
..... Click the link for more information.
The term DNA sequencing encompasses biochemical methods for determining the order of the nucleotide bases, adenine, guanine, cytosine, and thymine, in a DNA oligonucleotide.
..... Click the link for more information.
Nuclear DNA , nuclear deoxyribonucleic acid (nDNA), is DNA contained within a nucleus of eukaryotic organisms. In most cases it encodes more of the genome than the mitochondrial DNA and is passed sexually rather than matrilineally.
..... Click the link for more information.
Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.
Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. Most other DNA present in eukaryotic organisms is found in the cell nucleus. Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derived from the
..... Click the link for more information.
Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.
Proteobacteria
Stackebrandt et al., 1986

Orders

Alpha Proteobacteria
   Caulobacterales - e.g. Caulobacter
   Parvularculales
   Rhizobiales - e.g.
..... Click the link for more information.
Mitochondrial Eve (mt-mrca) is the name given by researchers to the woman who is defined as the matrilineal most recent common ancestor (MRCA) for all living humans.
..... Click the link for more information.
The nature versus nurture debates concern the relative importance of an individual's innate qualities ("nature", i.e. nativism, or philosophical empiricism, innatism) versus personal experiences ("nurture") in determining or causing individual differences in physical and behavioral
..... Click the link for more information.
intelligence quotient or IQ is a score derived from one of several different standardized tests attempting to measure intelligence. IQ tests are used as predictors of educational achievement. People with low IQ scores are sometimes placed in special-needs education.
..... Click the link for more information.
The subject of the inheritance of intelligence is the genetics of mental abilities. Research in this field is facing a number of difficulties, because intelligence as a trait is a fuzzy concept.
..... Click the link for more information.
nativism is the view that certain skills or abilities are 'native' or hard wired into the brain at birth. This is in contrast to the 'blank slate' or tabula rasa view which states that the brain has little innate ability and almost everything is learned through interaction with the
..... Click the link for more information.
Tabula rasa (Latin: scraped tablet or clean slate) refers to the epistemological thesis that individual human beings are born with no innate or built-in mental content, in a word, "blank", and that their entire resource of knowledge is built up gradually
..... Click the link for more information.
Eugenics is a social philosophy which advocates the improvement of human hereditary traits through various forms of intervention.[1] Throughout history, eugenics has been regarded by its various advocates as a social responsibility, an altruistic stance of a society,
..... Click the link for more information.
Compulsory sterilization programs are government policies which attempt to force people to undergo surgical sterilization. In the first half of the twentieth century, many such programs were instituted in many countries around the world, usually as part of eugenics programs
..... Click the link for more information.
Adolf Hitler (20 April 1889 – 30 April 1945) was the leader of the National Socialist German Workers Party (The Nazi party). He was appointed Chancellor of Germany in 1933, and became Führer (leader)[2] in 1934, remaining in power until his suicide in 1945.
..... Click the link for more information.
Social consciousness is consciousness shared within a society. It can also be defined as social awareness; to be aware of the problems that different societies and communities face on a day-to-day basis; to be conscious of the difficulties and hardships of society.
..... Click the link for more information.
David Reimer (August 22, 1965 – May 4, 2004) was a Canadian man who was born as a healthy boy, but was sexually reassigned and raised as female after his penis was inadvertently destroyed during circumcision.
..... Click the link for more information.
Races may mean:
  • the plural of Race, a genetic branch of a species (especially man)
  • Racing, speed-based competition
  • the acronym RACES, Radio Amateur Civil Emergency S

..... Click the link for more information.


Evolutionary psychology (abbreviated EP) is a theoretical approach to psychology that attempts to explain mental and psychological traits—such as memory, perception, or language—as adaptations, i.e., as the functional products of natural selection.
..... Click the link for more information.
This article or section may contain original research or unverified claims.
Please help Wikipedia by adding references. See the for details.
This article has been tagged since September 2007.

..... Click the link for more information.
A genetic disorder is a condition caused by abnormalities in genes or chromosomes. While some diseases, such as cancer, are due to genetic abnormalities acquired in a few cells during life, the term "genetic disease" most commonly refers to diseases present in all cells of the body
..... Click the link for more information.
A genetic disorder is a condition caused by abnormalities in genes or chromosomes. While some diseases, such as cancer, are due to genetic abnormalities acquired in a few cells during life, the term "genetic disease" most commonly refers to diseases present in all cells of the body
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.