If physically linked on a single chromosome, the round and yellow alleles would segregate together, and the wrinkled and green alleles would segregate together, no round green seeds or wrinkled yellow seeds would ever appear. Others Others. This is a universal law and always during gamete formation in all sexually reproducing organisms, the two factors of a pair pass into different gametes. cookielawinfo-checkbox-functional 11 months The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". Most alleles produce variations of the essay on genetics trait, but some produce very different phenotypes, essay on genetics. Mendel hypothesized that genes were inherited in pairs, one from the male and one from the female parent.
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Home — Essay Samples — Science — Genetics. We use cookies to personalyze your web-site experience. Essay examples. Topics in this category. Analysis of The Family History essay on genetics Jesus words 4 Pages. In case the genomic time can be said to have an exact birth date, it was within the middle of the appearance of the series, on April 14, That was when the worldwide exertion known as the Human Genome Extend put an effort to What is Eugenics Eugenics is recognised as a science that involves controlled breeding within a population to improve the occurrence of desirable traits and decrease the inheritance of genetic diseases and undesirable traits.
The topic of Eugenics affects several Catholic Views of Social Justice. One Social Justice in particular that directly affects the view of Catholics is Ecological Justice. Ecological Justice is being concerned with the obligations that humans have to the rest of creation, essay on genetics. Eugenics is the Genetic engineering, in definition, essay on genetics, is the artificial manipulation, modification, and recombination of DNA or other nucleic acid molecules in order to modify an organism or a population of organisms. Genetic engineering is beneficial in many ways. In an experiment setting, essay on genetics, the technology was demonstrated to In this essay I have analyzed and critically evaluated the findings of four researches conducted with the goal to find the link between genes and aggression.
I have also tried to determine how likely it is that these genes make an individual more prone to Essay on genetics Introduction In modern society, when people are enjoying the convenience brought by powerful technology and science, they also hope to essay on genetics this status forever. This, without doubt, leads us to the word: immortality. In order to learn this term, it is easy to start With each passing minute, the world population increases by hundreds, and to support the ever-increasing population, food is required, essay on genetics. To cope up with this food demand, various methods are being devised since decades. This method, unlike any Amongst the rapidly growing field of genetics lies a rather peculiar process which once was the pinnacle of Science Fiction now a certain absolute in reality — Cloning.
Regardless of any controversial issues surrounding this process, it is now more widely used than ever and The term gay is regularly utilized as an equivalent word for gay person; female homosexuality is frequently called as lesbianism, essay on genetics. The geneticists had found that genetic factors may influence the homosexuality GMOs are transgenic organisms carrying foreign genes either from virus, bacteria, essay on genetics, plants, humans in order to improve their genetic structure for particular purposes. In this procedure the beneficial or gene of interest is identified which is then isolated and multiplied and then inserted into essay on genetics Researchers from Stanford University School of Medicine and the Palo Alto Veteran Affairs Health Care System have established a section of genetic mutations which govern cholesterol levels in the body and may also guide the development and use of cardiovascular and diabetes drugs.
This data This ORF essay on genetics positioned in the antisense side left of the ORF1 and ORF2 already known and called ORF0. Phytoestrogens are a group of heterogeneous herbal substances; they are called non-steroidal estrogens or estrogen-like molecules, as their structure is comparable to β-estradiol structure, phytoestrogens are diphonelic compounds however they are essay on genetics substance despite their structural resemblance with estradiol, Presently phytoestrogens group contains more than The Human Immunodeficiency Virus HIV has affected millions of people worldwide, more especially in sub-Saharan Africa. The number of infections that occurred in infants in was estimated at Out of this, approximately ninety mine percent of the infections in infants are acquired The cancer stem cell CSC hypothesis is regarded as a reasonable explanation for the rapid multiplication of cells in the disease.
They are self-sufficient cells which seem to have increase tumorigenicity and self-renewal, which allow them to expand more rapidly than normal cells. While the Introduction In the early years of scientific investigations in the field of heredity, the methods used to obtain data were considered genetical but once the physical basis of genetic conditions were recognized several studies were performed essay on genetics methods of both cytology and genetics, essay on genetics, using the Rhodiola rosea L. Studies have provided evidence of R.
rosea efficacy mainly in models of chronic stress; only scarce data exist on its effect in acute stress and the underlying mechanisms. The objective In were million cases of malaria in 91 essay on genetics and people were killed Feeling stressed about your essay? Starting from 3 hours delivery. Topics in this Category DNA Gene Eugenics Genetic Modification Human Genome Project. Got it. Haven't found the right essay? Get an expert to write you the one you need! Get your paper now. Professional writers and researchers. Sources and citation are provided.
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This method, unlike any Amongst the rapidly growing field of genetics lies a rather peculiar process which once was the pinnacle of Science Fiction now a certain absolute in reality — Cloning. Regardless of any controversial issues surrounding this process, it is now more widely used than ever and The term gay is regularly utilized as an equivalent word for gay person; female homosexuality is frequently called as lesbianism. The geneticists had found that genetic factors may influence the homosexuality GMOs are transgenic organisms carrying foreign genes either from virus, bacteria, plants, humans in order to improve their genetic structure for particular purposes.
In this procedure the beneficial or gene of interest is identified which is then isolated and multiplied and then inserted into the Researchers from Stanford University School of Medicine and the Palo Alto Veteran Affairs Health Care System have established a section of genetic mutations which govern cholesterol levels in the body and may also guide the development and use of cardiovascular and diabetes drugs. This data This ORF is positioned in the antisense side left of the ORF1 and ORF2 already known and called ORF0. Phytoestrogens are a group of heterogeneous herbal substances; they are called non-steroidal estrogens or estrogen-like molecules, as their structure is comparable to β-estradiol structure, phytoestrogens are diphonelic compounds however they are non-steroidal substance despite their structural resemblance with estradiol, Presently phytoestrogens group contains more than The Human Immunodeficiency Virus HIV has affected millions of people worldwide, more especially in sub-Saharan Africa.
The number of infections that occurred in infants in was estimated at , Out of this, approximately ninety mine percent of the infections in infants are acquired The cancer stem cell CSC hypothesis is regarded as a reasonable explanation for the rapid multiplication of cells in the disease. They are self-sufficient cells which seem to have increase tumorigenicity and self-renewal, which allow them to expand more rapidly than normal cells. While the Introduction In the early years of scientific investigations in the field of heredity, the methods used to obtain data were considered genetical but once the physical basis of genetic conditions were recognized several studies were performed using methods of both cytology and genetics, using the Rhodiola rosea L.
Studies have provided evidence of R. rosea efficacy mainly in models of chronic stress; only scarce data exist on its effect in acute stress and the underlying mechanisms. The objective In were million cases of malaria in 91 countries and people were killed Feeling stressed about your essay? Starting from 3 hours delivery. Topics in this Category DNA Gene Eugenics Genetic Modification Human Genome Project. Got it. In this case, Mendel crossed the plants with Round and Yellow seeds RRYY with plants with wrinkled and green seeds rryy. From his earlier monohybrid crosses, Mendel knew which traits were dominant- round and yellow.
So, in the F 1 generation, he expected all round, yellow seeds from crossing these pure bred varieties, and that is exactly what he observed. Mendel knew that each of the Fi progeny were dihybrids; in other words, they contained both alleles for each characteristic RrYy. He then crossed individual Fi plants with genotypes RrYy with one another. This is called a dihybrid cross. The outcome shows a phenotypic ratio of 9 of the offspring having yellow round peas, 3 having yellow wrinkled peas, 3 having green round peas and 1 having green wrinkled peas. This is a classic phenotypic ratio which is always the result in a dihybrid cross between two heterozygotes with unlinked traits.
The proportion of each trait was still approximately for both seed shape and seed colour. In other words, the resulting seed shape and seed colour looked as if they had come from two parallel monohybrid crosses; even though two characteristics were involved in one cross, these traits behaved as though they had segregated independently. From these data, Mendel developed the third principle of inheritance- the principle of independent assortment i. alleles at one locus segregate into gametes independently of alleles at other loci. Such gametes are formed in equal frequencies Fig. A trihybrid cross is a breeding experiment between P generation parental generation organisms that differ in three traits Fig. Essay on the Test Cross : A test cross is a way to explore the genotype, the genetic makeup of an organism.
Early use of the test cross was as an experimental mating test used to determine what alleles are present in the genotype. Consequently, a test cross can help to determine whether a dominant phenotype is homozygous or heterozygous for a specific allele. Diploid organisms, like humans, have two alleles at each genetic locus, or position, and one allele is inherited from each parent. Different alleles do not always produce equal outward effects or phenotypes. One allele can be dominant and mask the effect of a second recessive allele in a heterozygous organism that carries two different alleles at a specific locus. Recessive alleles only express their phenotype if an organism carries two identical copies of the recessive allele, meaning it is homozygous for the recessive allele. This means that the genotype of an organism with a dominant phenotype may be either homozygous or heterozygous for the dominant allele.
Therefore, it is impossible to identify the genotype of an organism with a dominant trait by visually examining its phenotype. A test cross is the means by which a scientist can determine whether an individual with a dominant phenotype has a homozygous AA or heterozygous Aa dominant genotype. The test cross involves mating the individual with the dominant phenotype to an individual with a recessive aa phenotype and observing the offspring produced. If the individual being tested is homozygous dominant, then all offspring will have a dominant phenotype, since all the offspring will have at least one A dominant allele. If the tested individual is heterozygous dominant, then half of the offspring will show the dominant phenotype, while the other half shows the recessive phenotype.
Essay on the Backcrossing : It is the crossing of a hybrid with one of its parents or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent or it is the crossing of a heterozygous organism and one of its homozygous parents. It is used in horticulture, animal breeding and in production of gene knockout organisms Fig. Essay on the Limitations of Mendelian System : The simple system of Mendelian genetics is very powerful and serves to explain the inheritance patterns of numerous traits.
However, many traits are controlled by many genes acting in tandem, and thus do not obey strict Mendelian patterns although their constituent genes may. Furthermore, many human traits are strongly influenced by the environment as well, and therefore their phenotypes cannot be said to be Mendelian though the genetic components may be. In sum, Mendelian patterns are important, but cannot be applied universally. Individual traits must be researched to find out if they obey typical Mendelian patterns. Essay on the Polygenic or Quantitative Inheritance : When a trait feature or character is controlled by a single gene it is termed monogenic inheritance.
Many traits or features are controlled by a number of different genes. For example, the skin colour of humans and the kernel colour of wheat results from the combined effect of several genes, none of which are singly dominant. Polygenes affecting a particular trait are found on many chromosomes. Each of these genes has equal contribution and cumulative the total effect. Three to four genes contribute towards formation of the pigment in the skin of humans. So there is a continuous variation in skin colour from very fair to very dark. Such inheritance controlled by many genes is termed quantitative inheritance or polygenic poly meaning due many genes inheritance. In polygenic inheritance, each dominant gene controls equally the intensity of the character.
The effect of the dominant genes in cumulative and the intensity of character or trait depend upon the number of dominant genes Fig. Essay on Multiple Alleles: Alleles are located in corresponding parts of homologous chromosomes, only one member of a pair can be present in a given chromosome and only two are present in a cell of a diploid. Alleles are genes that are members of the same gene pair, each kind of allele affecting a trait differently than the other. A diploid organism has, by its definition, only two alleles at one time, yet exceptions to the rules do appear. Many examples were found where more than two alternative alleles, also called multiple alleles, are present.
In these cases two or more different mutations must have taken place at the same locus but in different individuals or at different times. Multiple alleles are alternative states at the same locus. The different alleles of a series are usually represented by the same symbol. Subscripts and superscripts are used to identify different members of a series of alleles. Most alleles produce variations of the same trait, but some produce very different phenotypes. The most famous example of multiple alleles was discovered in rabbits. It was known that Albino rabbits were produced on occasion in variously coloured rabbit populations.
After conducting a monohybrid cross between a coloured and Albino rabbit, it was discovered that the members of a pair of alternative genes, either c a or C, must be responsible for coloured or albino rabbits. A cross of homozygous coloured CC and albino c a c a rabbits were made and the F1 generation was all coloured, while the F2 generation had three coloured and one albino. This showed that one pair of alleles was involved, the wild C and the mutant allele c a. It was determined that C was dominant over c a Fig. Essay on the Chromosomal Theory of Inheritance : Sutton and Boveri in observed by that maternal from mother and paternal from father character come together in the progeny which is diploid or2n and has chromosomes in pairs and later on segregate during the formation of gametes.
The gametes have a single chromosome from each pair and are haploid or n. Chromosomes from two parents come together in the same zygote as a result of the fusion of two gametes and again separate out during the formation of gametes. Chromosomes are filamentous bodies present in the nucleus and seen only during cell division. The above two observations proved that there is a remarkable similarity between the behavior of character during inheritance and that of chromosomes during meiosis. The somatic body cells of an organism, which are derived by the repeated division of zygote have two identical sets of chromosomes, i.
Out of these, one set of chromosomes is received from the mother maternal chromosomes and one set from the father paternal chromosomes. Two chromosomes of one type carrying same genes constitute a homologous pair. Humans have 23 pairs of chromosomes. The chromosomes of homologous pair separate out during meiosis at the time of gamete formation. The behavior of chromosomes during meiosis indicates that Mendelian factors or genes are located linearly on the chromosomes. With progress in molecular biology it is now known that a chromosome is made up of a molecule of DNA and segments of DNA are the genes.
In animals the sex is determined by the presence or absence of the Y chromosome. The X and Y chromosomes are not homologous but are completely different chromosomes which carry unique information. No human can exist without at least one X chromosome. There is a viable human phenotype that has one X chromosome and no companion X or Y. These individuals are said to have the Turner syndrome. Turner syndrome X 0 individuals are females who are of normal to above intelligence and usually have few deficiencies considering their lack of an entire chromosome. One major deficiency of Turner syndrome is sterility and non-development of secondary sexual characteristics.
Certain traits in humans and other organisms can demonstrate sex-linked inheritance of characteristics. This means that the inherited traits are present on the sex determining chromosomes the X or the Y. Since there appears to be more information on the X chromosome than on the Y chromosome of humans, most known sex-linked characteristics are actually X- linked characteristics. In sex-linked traits, such as colour-blindness, the gene for the trait is found on the X chromosome a sex chromosome. Sex-linked traits affect primarily males, since they have only one copy of the X chromosome male genotype: XY. Females, who have two copies of the X chromosome, are affected only if they are homozygous for the trait. Females can, however, be carriers for sex-linked traits, passing their X chromosomes on to their sons.
Sex-linked inheritance works as follows- if a female carrier and a normal male give birth to a daughter, she has a 1 in 2 chance of being a carrier of the trait like her mother. If the child is a son, he has a 1 in 2 chance of being affected by the trait. If a female carrier and an affected male give birth to a daughter, she will either be affected or be a carrier. If the child is a son, he will either be affected or be entirely free of the gene. Beginning with Queen Victoria of England in whom it was probably a spontaneous mutation , the haemophilia gene spread quickly throughout the European rulers who intermarried as a matter of course. The disease, which prevents blood from clotting properly and renders a minor injury a life-threatening event, claimed several young men of the royal line.
Especially since male heirs were preferred over female as successors to the thrones of Europe, the spread of such a debilitating disease was a major problem. If they had, his dihybrid cross results would have been much more confusing, and he might not have discovered the law of independent assortment. The law of independent assortment holds true as long as two different genes are on separate chromosomes. When the genes are on separate chromosomes, the two alleles of one gene A and a will segregate into gametes independently of the two alleles of the other gene B and b. Equal numbers of four different gametes will result- AB, aB, Ab, ab.
But if the two genes are on the same chromosome, then they will be linked and will segregate together during meiosis, producing only two kinds of gametes. For instance, if the genes for seed shape and seed colour were on the same chromosome and a homozygous double dominant yellow and round, RRYY plant was crossed with a homozygous double recessive green and wrinkled, rryy , the F 1 hybrid offspring, as usual, would be double heterozygous dominant yellow and round, RrYy. However, since in this example the R and Y are linked together on the chromosome inherited from the dominant parent, with r and y linked together on the other chromosome, only two different gametes can be formed- RY and ry.
Therefore, instead of 16 different genotypes in the F 2 offspring, only three are possible: RRYY, RrYy, rryy and instead of four different phenotypes, only the original two will exist. Notice that the inheritance pattern now resembles that seen in a monohybrid cross, with a phenotypic ratio, rather than the ratio expected from the dihybrid cross. If physically linked on a single chromosome, the round and yellow alleles would segregate together, and the wrinkled and green alleles would segregate together, no round green seeds or wrinkled yellow seeds would ever appear.
The above explanation, however, neglects the influence of the crossing over of genetic material that occurs during meiosis. The farther away two genes are from one another, the more likely an exchange point for crossing over will form between them. At these exchange points, the alleles of one gene switch to the opposite homologous chromosome, while the other gene alleles remain with their original chromosomes. When alleles switch places like this, the resulting gametes are called recombinant. In the example above, the original parental gametes would be RY and ry, while the recombinant gametes would be Ry and rY. Thus four different kinds of gametes will be formed, instead of only two formed when the genes were linked Fig.
If two genes are extremely close together, crossing over will almost never occur between them, and the recombinant gametes will almost never form. If they are very far apart on the chromosome, crossing over will almost certainly occur between them, and recombinant gametes will form just as often as if the genes were on different chromosomes 50 percent of recombinant. If the genes are at an intermediate distance from each other, crossing over may sometimes occur between them and sometimes not Fig. Therefore, the percentage of recombinant gametes reflected in the percentage of recombinant offspring correlates with the distance between two genes on a chromosome. By comparing the recombination rates of multiple different pairs of genes on the same chromosome, the relative position of each gene along the chromosome can be determined.
This method of ordering genes on a chromosome is called a linkage map. Essay on Mutations: Mutations are errors in the genotype that create new alleles and can result in a variety of genetic disorders. In order for a mutation to be inherited from one generation to another, it must occur in sex cells, such as eggs and sperm, rather than in somatic cells. The best way to detect a genetic disorder is karyotyping. Such a pattern will usually only occur if the disease is caused by an abnormality in a single gene. The mutations that cause these diseases occur in genes on the autosomal chromosomes, the chromosomes that determine bodily characteristics and exist in all cells, both sex and somatic, as opposed to sex-linked diseases.
Genetic disorders are initially arises as a new mutation that changes a single gene so that it no longer produces a protein that functions normally. A disease resulting from a mutation that an allele which produces a non-functional protein will be inherited in a recessive fashion so that the disease phenotype will only appear when both copies of the gene carry the mutation, resulting in a total absence of the necessary protein. If only one copy of the mutated allele is present, the individual is a heterozygous carrier, showing no signs of the disease but able to transmit the disease gene to the next generation.
Albinism is an example of a recessive illness, resulting from a mutation in a gene that normally encodes a protein needed for pigment production in the skin and eyes. Many recessive illnesses occur with much greater frequency in particular racial or ethnic groups that have a history of intermarrying within their own community. For example, Tay-Sachs disease is especially common among people of Eastern European Jewish descent. Other well-known autosomal recessive disorders include sickle-cell anaemia and cystic fibrosis. Usually, a dominant phenotype results from the presence of at least one normal allele producing a protein that functions normally.
In the case of a dominant genetic illness, there is a mutation that results in the production of a protein with an abnormal and harmful action. Only one copy of such an allele is needed to produce disease, because the presence of the normal allele and protein cannot prevent the harmful action of the mutant protein. A single mutant allele produces an abnormal version of the Huntington protein; this abnormal protein accumulates in particular regions of the brain and gradually kills the brain cells. Mutation of a single gene results in recessive and dominant characteristics. Some genetic disorders result from the gain or loss of an entire chromosome. Normally, paired homologous chromosomes separate from each other during the first division of meiosis. If one pair fails to separate, an event called non-disjunction, then one daughter cell will receive both chromosomes and the other daughter cell will receive none.
When one of these gametes joins with a normal gamete from the other parent, the resulting offspring will have either one or three copies of the affected chromosome, rather than the usual two. A single chromosome contains hundreds to thousands of genes. A zygote with three copies of a chromosome trisomy , instead of the usual two, generally cannot survive embryonic development. Chromosome 21 is a major exception to this rule; individuals with three copies of this small chromosome trisomy 21 develop the genetic disorder called Down syndrome. People with Down syndrome show at least mild mental disabilities and have unusual physical features including a flat face, large tongue, and distinctive creases on their palms.
The absence of one copy of a chromosome monosomy causes even more problems than the presence of an extra copy. Only monosomy of the X chromosome is compatible with life. Polyploidy occurs when a failure occurs during the formation of the gametes during meiosis. The gametes produced in this instance are diploid rather than haploid. If fertilization occurs with these gametes, the offspring receive an entire extra set of chromosomes. In humans, polyploidy is always fatal, though in many plants and fish it is not. Essay , Biology , Branches , Genetics , Essay on Genetics. Top Menu BiologyDiscussion. com Follow Us On: Facebook Twitter Google Plus Publish Now.
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