What is the difference between organisms that are heterozygous dominant and homozygous dominant?
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In one sense, the term “genotype”—like the term “genome”—refers to the entire set of genes in the cells of an organism. In a narrower sense, however, it can refer to different alleles, or variant forms of a gene, for particular traits, or characteristics. An organism’s genotype is in contrast with its phenotype, which is the individual’s observable characteristics, resulting from interactions between the genotype and the environment. Show
There is a complex connection between the genotype and the phenotype. Since the phenotype is the result of an interaction between genes and the environment, different environments can lead to different traits in individuals with a particular genotype. In addition, different genotypes can lead to the same phenotype. This happens because genes have different alleles. For some genes and traits, certain alleles are dominant while others are recessive. A dominant trait is one that shows up in an individual, even if the individual has only one allele">allele that produces the trait. Some aspects of eye color work this way. Brown eyes, for instance, are dominant over blue eyes. This is because a pigment called melanin produces the brown color, while having no pigment leads to blue eyes. Having just one allele for the dark pigment is enough to make your eyes brown. There actually are several different pigments that affect eye color, each pigment resulting from a particular gene. This is the reason why people can have green eyes, hazel eyes, or any of a range of eye colors apart from blue or brown. When discussing genotype, biologists use uppercase letters to stand for dominant alleles and lowercase letters to stand for recessive alleles. With eye color, for instance, “B” stands for a brown allele and “b” stands for a blue allele. An organism with two dominant alleles for a trait is said to have a homozygous dominant genotype. Using the eye color example, this genotype is written BB. An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb. Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb. Of these three genotypes, only bb, the homozygous recessive genotype, will produce a phenotype of blue eyes. The heterozygous genotype and the homozygous dominant genotype both will produce brown eyes, though only the heterozygous genotype can pass on the gene for blue eyes. The homozygous dominant, homozygous recessive, and heterozygous genotypes only account for some genes and some traits. Most traits actually are more complex, because many genes have more than two alleles, and many alleles interact in complex ways.
Human beings possess two sets of Chromosomes - Heterozygous and Homozygous. The terms Homozygous and Heterozygous are used to describe Allele pairs. A Homozygous individual carries a set of two identical (RR or rr) Alleles while a Heterozygous individual bears different Alleles (Rr). For example, let us consider the gene of the hair colour possessing two Alleles, one Allele code is responsible for black (r) while the other Allele code is responsible for black (R). Homozygous individuals will have the same colour Allele on a homologous pair of Chromosomes, either RR or rr, and Heterozygous individuals will hold different Alleles on a homologous pair of Chromosomes like Rr. Let us discuss what these pairs are and the difference between them. What are Homozygous and Heterozygous Pair of Chromosomes?HomozygousHuman beings possess the same gene. However, the number of Genes are varied, and this controls our physical health and traits. Each variation is called an Allele, and every individual inherits two alleles for each gene - one from their biological father and another from their birth mother. The term ‘Homozygous’ is an amalgamation of two words - Homo which refers to ’same‘, and zygous, which refers to ‘having zygotes of a specified kind‘. If the Alleles of a gene are identical, then the individual is Homozygous for that specific gene. For example, you could possess two identical or similar Alleles for a particular gene that causes hazel brown eyes. (Image will be Uploaded Soon) Some Alleles are dominant that is expressed more strongly while some Alleles are recessive which get masked by the dominant Alleles. However, in a Homozygous Genotype, the interaction between a dominant and a recessive Allele does not occur as the individual holds either two dominant Alleles known as Homozygous dominant(RR) ot two recessive Alleles known as Homozygous recessive(rr). HeterozygousWe know that each gene inherits two Alleles and the only difference is the versions of the Alleles. The term ‘Heterozygous’ is an amalgamation of two words - Hetero which refer to ‘different’ and zygous which refers to ‘having zygotes of a particular specified kind‘. This results in two different Alleles present on the homologous Chromosomes. An individual who possesses a Heterozygous Genotype will have two versions of Alleles (Rr). For example, in terms of hair colour, a Heterozygous individual can possess one Allele for brown hair and one Allele for red hair. The relationship between the two Alleles affects the traits expressed in an individual which also determines the characteristics which a carrier possesses. (Image will be uploaded soon) (Image will be uploaded soon) Homozygous vs Heterozygous
Autozygous and Allozygous Alleles (Alleles Based on origin)Zygosity in an individual may also refer to the origin of the Alleles in a given Genotype. In the case in which the two alleles at a locus originate from a common ancestor (for example through nonrandom mating (inbreeding)), the Genotype is known as Autozygous Alleles. Such conditions are referred to in genetic studies as being "identical by descent"(abbreviated as IBD). When the two Alleles come from different ancestors (at least to the extent that the ancestry can be traced), the Genotype is referred to as Allozygous Alleles. This phenomenon of identity is referred to as being "identical by state", (abbreviated as IBS). Because the Alleles/ Genes for an Autozygous Genotype are received from the same ancestor (source), they are always Homozygous in nature. However, in the case of Allozygous Alleles, Genotypes may be Homozygous or Heterozygous in expression. Heterozygous Genotypes are commonly, but not necessarily, Allozygous because different Alleles may have originated during the course of evolution by means of accumulating mutations sometimes after a common origin. The hemizygous and nullizygous Genotypes lack enough Alleles and hence they do not facilitate comparison studies on the basis of ancestry/ sources. This classification thus proves irrelevant for them. Monozygotic and Dizygotic TwinsAs discussed in the article here, "zygosity" is generally used in the context of a specific genetic locus. However, the word zygosity may also be useful in our understanding of the genetic similarity or dissimilarity between twins. Identical twins are monozygotic. This means that during their course of development, they are formed from the same zygote which has split into two and then developed into two embryos during implantation. Fraternal twins or non-identical twins are dizygotic as they develop from two separate oocytes (egg cells) that are fertilized by two different sperms during the fertilization process. Sesquizygotic twins are halfway between monozygotic and dizygotic and are believed to arise after two sperm fertilize a single oocyte which subsequently splits into two morulae. Want to read offline? download full PDF here Download full PDF Is this page helpful?  Recently Updated Pages Recently Updated Pages What is the difference between homozygous organism & heterozygous organisms?An organism that has the same two copies of a gene is considered homozygous for that trait, while an organism that has different copies of a gene for a particular trait is considered heterozygous for that trait. In plant and animal breeding, such organisms can be called homozygotes and heterozygotes.
What is the difference between heterozygous dominant and heterozygous recessive?If it's dominant, it means only one mutated copy is needed to result in disease. This is called a “dominant disease” or “dominant disorder.” If you're heterozygous for a dominant disorder, you have a higher risk of developing it. On the other hand, if you're heterozygous for a recessive mutation, you won't get it.
How do you know if its homozygous dominant or heterozygous?To identify whether an organism exhibiting a dominant trait is homozygous or heterozygous for a specific allele, a scientist can perform a test cross. The organism in question is crossed with an organism that is homozygous for the recessive trait, and the offspring of the test cross are examined.
What is the difference between homozygous and heterozygous recessive?The main difference between homozygous and heterozygous is that homozygous individuals carry two identical alleles whereas heterozygous individuals carry both dominant and recessive allele. The self-breeding between homozygous individuals produces offspring with the same trait over generations.
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