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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. Image File history File links Information_icon. ...
Image File history File links Derived from public domain images featured at: http://commons. ...
DNA, the molecular basis for inheritance. ...
It has been suggested that Biparental zygote be merged into this article or section. ...
The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ...
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
For the hard rock band, see Allele (band). ...
Every gene in a diploid organism has two alleles at the gene's locus. These alleles are defined as dominant or recessive, depending on the phenotype resulting from the two alleles. If a gene's two alleles are both dominant or both recessive, that specific gene is homozygous. If one allele is dominant and the other is recessive, the gene is heterozygous. The word dominant has several possible meanings: In music theory, the dominant or dominant note (second most important) of a key is that which is a perfect fifth above the tonic; in just intonation the note whose pitch is 1. ...
In genetics, the term recessive gene refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele). ...
The terms homozygous, heterozygous and hemizygous are used to simplify the description of the genotype of a diploid organism at a single genetic locus. At a given gene or position along a chromosome (a locus), the DNA sequence can vary among individuals in the population. The variable DNA segments are referred to as alleles, and diploid organisms generally have two alleles at each locus, one allele for each of the two homologous chromosomes. Simply stated, homozygous describes two identical alleles or DNA sequences at one locus, heterozygous describes two different alleles at one locus, and hemizygous describes the presence of only a single copy of the gene in an otherwise diploid organism. This article does not cite its references or sources. ...
Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ...
Short and long arms Chromosome. ...
Homologous chromosomes are chromosomes in a biological cell that pair (synapse) during meiosis, or alternatively, non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information, called alleles, at those genes. ...
Zygosity is also used to describe the genetic condition of the zygote(s) from which twins emerge, where it refers to the similarity or dissimilarity of the twins' DNA. Identical twins are monozygotic - they develop from one zygote (one fertilized egg that develops into two embryos). Fraternal twins are dizygotic - they developed separately from two zygotes (two fertilized eggs). For a description of these terms, see twins. Fraternal twins at two weeks old. ...
Fraternal twin boys in the tub The term twin most notably refers to two individuals (or one of two individuals) who have shared the same uterus (womb) and usually, but not necessarily, born on the same day. ...
Fraternal twins at two weeks old. ...
Homozygous
An organism is referred to as being homozygous (Basically meaning of the same alleles) at a specific locus when it carries two identical copies of the gene affecting a given trait on the two corresponding homologous chromosomes (e.g., the genotype is PP or pp when P and p refer to different possible alleles of the same gene). Such a cell or such an organism is called a homozygote. Homologous chromosomes are chromosomes in a biological cell that pair (synapse) during meiosis, or alternatively, non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information, called alleles, at those genes. ...
This article does not cite its references or sources. ...
A homozygous dominant genotype occurs when a particular locus has two copies of the dominant allele (e.g. PP). A homozygous recessive genotype occurs when a particular locus has two copies of the recessive allele (e.g. pp). In genetics, the term dominant gene refers to the allele that causes a phenotype that is seen in a heterozygous genotype. ...
It has been suggested that this article or section be merged into Dominance relationship. ...
Pure-bred or true breeding organisms are homozygous. For example a homozygous individual could have the allele combinations PP or pp. All homozygous alleles are either allozygous or autozygous. A true breeding organism, sometimes also called a pure-bred, is an organism having certain biological traits which are passed on to all subsequent generations when bred with another true breeding organism for the same traits. ...
Allozygous Allozygosity is when two alleles are alike, but unrelated. The two alleles had different ancestral alleles that through convergent evolution became similar. In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ...
Autozygous Autozygosity is when two alleles are alike by relation, that is to say since they had a common ancestor, and they are similar.
Heterozygous An organism is a heterozygote or is heterozygous at a locus or gene when it has different alleles occupying the gene's position in each of the homologous chromosomes. In other words, it describes an individual that has 2 different alleles for a trait. In diploid organisms, the two different alleles were inherited from the organism's two parents. For example a heterozygous individual would have the allele combination Pp. Homologous chromosomes are chromosomes in a biological cell that pair (synapse) during meiosis, or alternatively, non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information, called alleles, at those genes. ...
A parent is a father or mother; one who begets or one who gives birth to or nurtures and raises a child; a relative who plays the role of guardian // Mother This article or section does not cite its references or sources. ...
Hemizygous Hemizygous describes a diploid individual who has only one allele of a gene or chromosome segment rather than the usual two. A hemizygote refers to a cell or organism whose genome includes only one allele at a given locus. For organisms where the male is heterogametic, such as humans, it refers in particular to X-linked genes, since males normally possess only one X-chromosome. They are hemizygous for (nearly) all genes that are located on the X-chromosome. Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ...
For the hard rock band, see Allele (band). ...
For a non-technical introduction to the topic, see Introduction to Genetics. ...
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ...
It has been suggested that sex chromosome be merged into this article or section. ...
Sex-linked genes are those carried on the mammalian X chromosome but not the Y chromosome. ...
In a more extreme example, male honeybees (Drones) are hemizygous organisms since they develop from unfertilized eggs and their entire genome is haploid. Blue-Russian drone honeybees drinking. ...
Inheritance of traits -
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The relationship between different alleles and the phenotypes that they affect is described in Dominance relationship. Some alleles are neither dominant nor recessive to another allele. In such cases, both alleles affect the phenotype of the heterozygote. Sometimes the result is an intermediate phenotype, such as when a snapdragon plant producing red flowers is crossed to one producing white flowers: the result is a heterozygous plant producing pink flowers. This is called incomplete dominance. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics. ...
It has been suggested that dominant allele be merged into this article or section. ...
It has been suggested that dominant allele be merged into this article or section. ...
To symbolize how a gene is inherited, the dominant allele is indicated with an upper case character and the recessive with a lower case character. The colour of flowers in Mendel's inheritance experiments are often indicated as PP for the dominant homozygote, which produces a red flower, and pp for the recessive homozygote, which produces a white flower. When these two are crossed, the F1 or first filial generation receives one chromosome with the P allele from the red-flowered parent and a corresponding chromosome with the p allele from the white-flowered parent. All of the F1 generation are heterozygous, and this genotype is indicated with Pp. All of the F1 plants produce red flowers, as this is the dominant allele. Gregor Johann Mendel (July 20, 1822[1] – January 6, 1884) was a Moravian[2] Augustinian priest and scientist often called the father of modern genetics for his study of the inheritance of traits in pea plants. ...
It has been suggested that dominant allele be merged into this article or section. ...
It has been suggested that dominant allele be merged into this article or section. ...
Heterozygosity Heterozygosity refers to the state of being a heterozygote. Heterozygosity can also refer to the fraction of loci within an individual that are heterozygous. In population genetics, it is commonly extended to refer to the population as a whole, i.e. the fraction of individuals in a population that are heterozygous for a particular locus. Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ...
Typically, the observed(Ho) and expected(He) heterozygosities are compared, defined as follows for diploid individuals in a population:
- Observed
where n is the number of individuals in the population, and ai1,ai2 are the alleles of individual i at the target locus. - Expected
where m is the number of alleles at the target locus, and fi is the frequency of the ith allele at the target locus.
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