Each person normally has one pair of sex chromosomes in each cell. As a general rule, the Y chromosome is present in males, who have one X and one Y chromosome, while females have two X chromosomes. However there are exceptions where this is not the case, for details see Intersex. Many of the genes on the Y chromosome are involved in male sexual determination and development; the most important of them is the SRY gene, which seems to determine the sex in primates. ...

See also:

Y chromosome, Y chromosome - Function, Y chromosome - Origins, Y chromosome - Chromosomal conditions related to chromosome Y, Y chromosome - Repair of the Y chromosome, Y chromosome - Y chromosome in Genetic Genealogy

Read more here: » Y chromosome: Encyclopedia II - Y chromosome - Function

Twin - Fraternal twins. Fraternal twins (commonly known as "non-identical twins") usually occur when two fertilized eggs are implanted in the uterine wall at the same time. The two eggs form two zygotes, and these twins are therefore also known as dizygotic. Dizygotic twins, like any siblings, have a very small chance of having the exact same chromosome profile, but most likely have a number of different chromosomes that distinguish them. Dizygotic twins may be a different sex or the sam ...

See also:

Twin, Twin - Types of twins, Twin - Fraternal twins, Twin - Identical twins, Twin - Complications of twin pregnancy, Twin - Vanishing twins, Twin - Conjoined twins, Twin - Parasitic twins, Twin - Miscarried twin, Twin - Human twins, Twin - Multiple births, Twin - Predisposing factors, Twin - Twin studies, Twin - Unusual Twinnings, Twin - Twinning in animals

Read more here: » Twin: Encyclopedia II - Twin - Types of twins

The incidence of Down syndrome is estimated at 1 per 800 births, making it the most common human aneuploidy. Maternal age influences the chance of conceiving a baby with the syndrome. At age 20 to 24, it is 1/1490, while at age 40 it is 1/106, and at age 49 is 1/11. (Hook EB., 1981). Although the chance increases with maternal age, most children with Down syndrome (80%) are born to women under the age of 35. This reflects the overall fecundity of that age group. Many standard screens of pregnancies indicate Down syndrome, although they are n ...

See also:

Down syndrome, Down syndrome - Overview, Down syndrome - History, Down syndrome - Genetics, Down syndrome - Prenatal Screening, Down syndrome - Education, Down syndrome - Health, Down syndrome - Medical research, Down syndrome - Challenges, Down syndrome - Pregnant women with a diagnosis of Down syndrome, Down syndrome - Parents of children with Down syndrome, Down syndrome - Individuals with Down syndrome, Down syndrome - Down syndrome's sociology, Down syndrome - Notable individuals, Down syndrome - Down syndrome in fiction, Down syndrome - Sources

Read more here: » Down syndrome: Encyclopedia II - Down syndrome - Overview

The mesothelium consists of a single layer of flattened to cuboidal cells forming the epithelial lining of the serous cavities of the body including the peritoneal, pericardial and pleural cavities. Deposition of asbestos fibres in the parenchyma of the lung may result in the penetration of the visceral pleura from where the fibre can then be carried to the pleural surface, thus leading to the development of malignant mesothelial plaques. The processes leading to the development of peritoneal mesothelioma remain unresolved, although it has b ...

See also:

Mesothelioma, Mesothelioma - Signs and symptoms, Mesothelioma - Diagnosis, Mesothelioma - Screening, Mesothelioma - Staging, Mesothelioma - Pathophysiology, Mesothelioma - Epidemiology, Mesothelioma - Incidence, Mesothelioma - Risk factors, Mesothelioma - Exposure, Mesothelioma - Treatment, Mesothelioma - Surgery, Mesothelioma - Radiation, Mesothelioma - Chemotherapy, Mesothelioma - Immunotherapy, Mesothelioma - Heated Intraoperative Intraperitoneal Chemotherapy, Mesothelioma - Research, Mesothelioma - Legal issues, Mesothelioma - History, Mesothelioma - Sources

Read more here: » Mesothelioma: Encyclopedia II - Mesothelioma - Pathophysiology

A male donkey can be crossed with a female horse to produce a mule. A male horse can be crossed with a female donkey (jennet or jenny) to produce a hinny. These hybrids are almost always sterile because horses have 64 chromosomes whereas donkeys have 62, producing offspring with 63 chromosomes. Due to different mating behavior, jacks are often more willing to cover mares than stallions are to breed jennets. Mules are much more common than hinnies. This is believed to be caused by two factors, the first being proven in cat hybrids, that when ...

See also:

Donkey, Donkey - Etymology of the name, Donkey - Relationship to horses, Donkey - Economic use, Donkey - Wild asses, Donkey - Burro, Donkey - External burro links, Donkey - Cultural aspects, Donkey - abusive meaning, Donkey - US Democratic Party symbol, Donkey - Other uses

Read more here: » Donkey: Encyclopedia II - Donkey - Relationship to horses

In humans, sex is conventionally perceived as a dichotomous state or identity for most biological and social purposes, such that a person can only be female or male. However, when the criteria which are generally used to define femaleness or maleness are examined more closely, it becomes apparent that the assignment or determination of 'sex' occurs at multiple levels. Environmental, biological, social, psychological and other factors are all believed to have some role in this process, and the complex intera ...

See also:

Sex, Sex - Sex in non-animal species, Sex - Sex among humans, Sex - Discordance, Sex - Biological varieties of discordance, Sex - Psychological behavioral and cultural varieties of discordance, Sex - Social and legal considerations

Read more here: » Sex: Encyclopedia II - Sex - Sex among humans

The term C-value refers to the amount of DNA contained within a haploid nucleus (e.g., in a gamete or one half the amount in a diploid somatic cell) of a eukaryotic organism. In some cases (notably among diploid organisms), the terms C-value and genome size are used interchangeably, however in polyploids the C-value may represent two genomes contained within the same nucleus. Greilhuber et al. (2005) have suggested some new layers of terminology and associated abbreviations to clari ...

Including:

• C-value - Definition
• C-value - Origin of the term
• C-value - Variation among species

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Cancer - Origins of cancer. Cell division (proliferation) is a physiological process that occurs in almost all tissues and under many circumstances. Normally the balance between proliferation and cell death is tightly regulated to ensure the integrity of organs and tissues. Mutations in DNA that lead to cancer disrupt these orderly processes. The uncontrolled and often rapid proliferation of cells can lead to either a benign tumor or a malignant tumor (cancer). Benign tumors do not spread to other p ...

See also:

Cancer, Cancer - Terminology, Cancer - History, Cancer - Classification and nomenclature, Cancer - Adult cancers, Cancer - Childhood cancers, Cancer - Causes and pathophysiology, Cancer - Origins of cancer, Cancer - Molecular biology, Cancer - Morphology, Cancer - Heredity, Cancer - Environment and diet, Cancer - Epidemiology, Cancer - Prevention, Cancer - Diet and cancer, Cancer - Other chemoprevention agents, Cancer - Genetic testing, Cancer - Diagnosing cancer, Cancer - Signs and symptoms, Cancer - Biopsy, Cancer - Screening, Cancer - Treatment of cancer, Cancer - Surgery, Cancer - Chemotherapy, Cancer - Immunotherapy, Cancer - Radiation therapy, Cancer - Hormonal suppression, Cancer - Symptom control, Cancer - Treatment trials, Cancer - Complementary and alternative medicine, Cancer - Cancer vaccines, Cancer - Coping with cancer, Cancer - Social impact, Cancer - Cancer research

Read more here: » Cancer: Encyclopedia II - Cancer - Causes and pathophysiology

Studies of Bulgarian, Baltic and Vlax Roma genetics suggest that about 50% of observed Y chromosomes and mitochondrial DNA belong to male haplogroup H and female haplogroup M, respectively. Both of these are widespread across South and Central Asia. In summary, males consist in the main of haplogroups H (50%), I (22%) and J2 (14%), Rlb (7%) approx; females H (35%), M (26%), U3 (10%), X (7%), other (20%). Whereas male haplogroup H and female M are rare in non-Roma European populations, the rest are found throughout Europe. However female hapl ...

See also:

Roma people, Roma people - Name, Roma people - Language, Roma people - History, Roma people - People, Roma people - Genetics, Roma people - Rejection, Roma people - Former communist countries, Roma people - Roma society, Roma people - Religion, Roma people - Music, Roma people - Fictional representations of Roma, Roma people - Groups with similar lifestyles

Read more here: » Roma people: Encyclopedia II - Roma people - Genetics

Cystic fibrosis is exclusively heritable as both parents must carry the recessive genes for a child to acquire the disease. At the genetic level, cystic fibrosis is most often the result of an in-frame deletion of three base pairs in the DNA. Cystic fibrosis results from the production of an abnormal form of a protein called cystic fibrosis transmembrane conductance regulator (CFTR). CFTR functions in transporting chloride ions across epithelial cells found in the lung and intestinal tract. In CF patients, CFTR does not function properly, ca ...

See also:

Cystic fibrosis, Cystic fibrosis - Symptoms, Cystic fibrosis - History and statistics, Cystic fibrosis - Biological causes, Cystic fibrosis - Complications, Cystic fibrosis - Cross-infection, Cystic fibrosis - Digestion, Cystic fibrosis - Diabetes, Cystic fibrosis - Fertility, Cystic fibrosis - Other complications, Cystic fibrosis - Treatment, Cystic fibrosis - Notable people with cystic fibrosis

Read more here: » Cystic fibrosis: Encyclopedia II - Cystic fibrosis - Biological causes

In populations with high rates of carriage (Ashkenazi Jews and Norrbottnian Swedes), some family members of the index patient may already have been diagnosed with Gaucher's. Truly sporadic cases may suffer diagnostic delay due to the protean symptoms. Biochemical abnormalities: high alkaline phosphatase, angiotensin-converting enzyme (ACE) and immunoglobulin levels. The diagnosis is made with genetic testing of the β-glucosidase gene. As there are numerous different mutations, sequencing of the gene is sometimes necessary to confirm the diagnosis. Prenatal diagnosis is available, and is us ...

See also:

Gaucher's disease, Gaucher's disease - Subtypes, Gaucher's disease - Signs and symptoms, Gaucher's disease - Diagnosis, Gaucher's disease - Pathophysiology, Gaucher's disease - Classification and genetics, Gaucher's disease - Epidemiology, Gaucher's disease - Treatment, Gaucher's disease - History

Read more here: » Gaucher's disease: Encyclopedia II - Gaucher's disease - Diagnosis

Wisent, also called European bison, faced extinction in the early 20th century. The 3600 animals living in 2000 are all descended from 12 individuals and only two distinct Y chromosomes are left in the species. The population of American Bison fell due to overhunting, nearly leading to extinction around the year 1890 and has since begun to recover. A classic example of a population bottleneck is that of the Northern Elephant Seals, whose population fell to about 30 in the 1890's although it now numbers in the tens of thousands. Anothe ...

See also:

Population bottleneck, Population bottleneck - Humans, Population bottleneck - Examples in the animal world, Population bottleneck - Notes

Read more here: » Population bottleneck: Encyclopedia II - Population bottleneck - Examples in the animal world

PAI-1 is mainly produced by the endothelium (cells lining blood vessels), but is also secreted by other tissue types, such as adipose tissue. PAI-1 inhibits the serine proteases tPA and uPA/urokinase, and hence is an inhibitor of fibrinolysis, the physiological process that degrades blood clots. ...

See also:

Plasminogen activator inhibitor-1, Plasminogen activator inhibitor-1 - Genetics, Plasminogen activator inhibitor-1 - Function, Plasminogen activator inhibitor-1 - Role in disease, Plasminogen activator inhibitor-1 - Pharmacology, Plasminogen activator inhibitor-1 - Reference, Plasminogen activator inhibitor-1 - External link

Read more here: » Plasminogen activator inhibitor-1: Encyclopedia II - Plasminogen activator inhibitor-1 - Function

Main article: Mechanical properties of DNA. DNA - Strands association and dissociation. The hydrogen bonds between the strands of the double helix are weak enough that they can be easily separated by enzymes. Enzymes known as helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The strands can also be separa ...

See also:

DNA, DNA - Overview, DNA - DNA in practice, DNA - DNA in crime, DNA - DNA in computation, DNA - Overview of molecular structure, DNA - The role of the sequence, DNA - DNA replication, DNA - Mechanical properties relevant to biology, DNA - Strands association and dissociation, DNA - Circular DNA, DNA - Great length versus tiny breadth, DNA - Entropic stretching behavior, DNA - Different helix geometries, DNA - Non-helical forms, DNA - Direction of DNA strands, DNA - Chemical nomenclature 5' and 3', DNA - Sense and antisense, DNA - Distinction between sense and antisense strands, DNA - As viewed by topologists, DNA - Single-stranded DNA ssDNA and repair of mutations, DNA - The history of DNA research, DNA - First isolation of DNA, DNA - Establishing a link between heritable traits and chromosomes, DNA - Discovery of the structure of DNA, DNA - Bibliography

Read more here: » DNA: Encyclopedia II - DNA - Mechanical properties relevant to biology

During pregnancy, the woman undergoes many physiological changes, which are entirely normal, including cardiovascular, renal, hematologic, metabolic or respiratory changes that become very important in the event of complications. Obstetrics - Metabolism. During pregnancy, both protein metabolism and carbohydrate metabolism are affected. One kilogram of extra protein is deposited, with half going to the fetus and placenta, and another half going to uterine contractile proteins, breast ...

See also:

Obstetrics, Obstetrics - Antenatal care, Obstetrics - Symptoms, Obstetrics - Trimesters, Obstetrics - Overall, Obstetrics - Maternal physiology, Obstetrics - Metabolism, Obstetrics - Nutrition, Obstetrics - Cardiovascular, Obstetrics - Pulmonary, Obstetrics - Hematology, Obstetrics - Gastrointestinal, Obstetrics - Renal, Obstetrics - Endocrine, Obstetrics - Musculoskeleton and dermatology, Obstetrics - Others, Obstetrics - Prenatal Care, Obstetrics - First trimester, Obstetrics - Second trimester, Obstetrics - Third trimester, Obstetrics - Complications, Obstetrics - Fetal assessments, Obstetrics - Induction, Obstetrics - Labour, Obstetrics - Emergencies in obstetrics, Obstetrics - Imaging monitoring and care, Obstetrics - Antenatal record, Obstetrics - Imaging, Obstetrics - Terms and definitions

Read more here: » Obstetrics: Encyclopedia II - Obstetrics - Maternal physiology

Cancer is the uncontrolled growth of cells due to damage to DNA (mutations) and, occasionally, due to an inherited propensity to develop certain tumours. Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body - in other words, the body attacks its own cells. In a contrast, transplant rejection happens because a normal healthy human immune system can distinguish foreign tissues and attempts to destroy them. Also the reverse situation, called ...

See also:

Chemotherapy, Chemotherapy - History, Chemotherapy - Principles, Chemotherapy - Types, Chemotherapy - Alkylating agents L01A, Chemotherapy - Anti-metabolites L01B, Chemotherapy - Plant alkaloids and terpenoids L01C, Chemotherapy - Topoisomerase inhibitors L01CB and L01XX, Chemotherapy - Antitumour antibiotics L01D, Chemotherapy - Hormonal therapy, Chemotherapy - Dosage, Chemotherapy - Delivery, Chemotherapy - Treatment schemes, Chemotherapy - Side-effects, Chemotherapy - Immunosuppression and myelosuppression, Chemotherapy - Nausea and vomiting, Chemotherapy - Other side effects

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The members of R1b are the descendants of the first modern humans, the Cro-Magnon, who entered Europe about 35,000 years ago. The Cro-Magnons were the first documented human artists, making sophisticated cave paintings. Famous sites include Lascaux in France, Cueva de las Monedas in Spain and Valley of Foz Côa in Portugal (the biggest open air site in Europe). The Cro-Magnons were contemporaries of European Neandertals, who died out not long after the first modern humans spread out. While there are theories of a genocide occurring, there is no archaeological evidence supporting this. The Neandertals' last refu ...

See also:

Haplogroup R1b YDNA, Haplogroup R1b YDNA - Origins

Read more here: » Haplogroup R1b YDNA: Encyclopedia II - Haplogroup R1b YDNA - Origins

Eye color - Brown eyes. The vast majority of the world's people have dark eyes, ranging from brown to nearly black. Light brown eyes are also present in many people, but to a lesser extent. Most of the original inhabitants of Africa, Asia, and the Americas have brown eyes. Brown eyes are also found in Europe, Oceania and North America, though within European populations they are not predominate to the same extent. In this population, brown eyes are genetically linked to brown or black hair. See also:

Eye color, Eye color - Colors, Eye color - Brown eyes, Eye color - Black eyes, Eye color - Hazel eyes, Eye color - Blue eyes, Eye color - Grey eyes, Eye color - Green eyes, Eye color - Blue-Green eyes, Eye color - Red eyes, Eye color - Heterochromia, Eye color - Genetics

Read more here: » Eye color: Encyclopedia II - Eye color - Colors

Some well-known patients include: Geraldine Ferraro Mel Stottlemyre Don Baylor Mel Goldstein Roy Scheider Deceased: Ann Landers Mark Lenard ...

See also:

Multiple myeloma, Multiple myeloma - Signs and symptoms, Multiple myeloma - Diagnosis, Multiple myeloma - Investigations, Multiple myeloma - Workup, Multiple myeloma - Criteria, Multiple myeloma - Staging, Multiple myeloma - Pathophysiology, Multiple myeloma - Epidemiology, Multiple myeloma - Treatment, Multiple myeloma - Initial therapy, Multiple myeloma - Relapse, Multiple myeloma - Prognosis, Multiple myeloma - Patients

Read more here: » Multiple myeloma: Encyclopedia II - Multiple myeloma - Patients

Bladder cancer: Some gene mutations are acquired during a person's lifetime and are present only in certain cells. These changes are called somatic mutations and are not inherited. Somatic mutations in the TP53 gene have been found in some cases of bladder cancer. Most of these mutations replace one amino acid (a building block of proteins) with another amino acid in tumor protein p53. The altered protein cannot bind to DNA correctly, which prevents the protein from effectively regulating cell growth and division. As a result, DNA damage acc ...

See also:

TP53, TP53 - Related conditions

Read more here: » TP53: Encyclopedia II - TP53 - Related conditions

The male platypus reproductive structure is much like that of other mammals. One exception is that their testicles are inside their body, near their kidneys. The female reproductive system, on the other hand, differs from other placental mammals. Their paired ovaries resemble those of birds and reptiles. Although the platypus has two separate ovaries, only the left one is functional. The other is primitive and u ...

See also:

Platypus, Platypus - Taxonomy, Platypus - Physical description, Platypus - Venom, Platypus - Electrolocation in the platypus, Platypus - Reproduction, Platypus - Ecology and behaviour, Platypus - The platypus in mammalian evolution, Platypus - Conservation status, Platypus - Mascots, Platypus - References and links

Read more here: » Platypus: Encyclopedia II - Platypus - Reproduction