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Mendel's Genetic Laws - Principles

Paper Type: Free Essay Subject: Biology
Wordcount: 3130 words Published: 24th May 2018

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Deoxyribonucleic acid, more known as DNA, is a genetic material that exists in all living organisms. Within DNA there is a short segment that involves genes, and these genes are what have been passed down from parents to their children. A gene is a specific order of nucleotides producing pieces of a chromosome that are conveying information from parents to their offspring, and is held responsible to regulate some of the characteristics that are set on the offspring. There are said to be around 20,000 genes to a human, of which are found in a chromosome and usually made up into pairs. A human-cell contains 23 pairs of chromosomes adding up to a total of 46, but the amount of chromosomes different species alters. Of these 46 chromosomes, sperm and egg cells of the human body only need to take just 23 of those chromosomes. Chromosomes hold the formula for creating a living organism (genes are the ingredients and hold a key protein to the recipe) and are created from lengthy, curled up molecules of DNA. They are found in almost every cell’s nucleus, of which it stores them and they carry certain information.


The Austrian monk Gregor Mendal was a big contribution in the history of genetics and successfully resolved the basic principles of heredity by using a creative experiment in breeding inbred lines of pea plants. Over a period of eight years experimenting using over 10,000 pea plants, Gregor Mendal would record the inheritance patterns in the offspring which set off his success in discovering the discipline of genetics. During his experiments Gregor Mendel found that genes genes only seemed to come in pairs and are then inherited as definite units, and just one would come from each parent and onto their offspring. Mendel’s Laws of Heredity consisted that of three: The Law of Segregation – of which he discovered that every genetic/inherited characteristic is construed by that of a gene pair. Genes provided by parents are divided at random for the sex cells so they are able to hold one of each, of which are then inherited to their offspring with one genetic allele from each parent during fertilization.


The Law of Independent Assortment – this is the discovery that the genes of an individual for contrasting traits are placed solely from each other in order for the traits to not be reliant on one another. The Law of Dominance – this law is when an organism is a repeated form of a gene is able to give out that the form is dominant.

For a child who has a parent of a homozygous non tongue roller (tt) and another parent if a heterozygous roller (Tt), then the outcome of the children would be that 50% would be able to tongue-roll and 50% would not be able to tongue roll. This is due to the compatibility of both a dominant and recessive gene and that only one allele is needed to enable for the offspring to tongue-roll. For this equation it is known as being a monohybrid cross, which means that the merging of various individuals who hold different alleles of one genetic position of interest.    

With both parents being heterozygous they’re both carrier genotypes of phenylthiocarbamide (PTC). Having two carriers (Tt) then the outcome for their offspring is varied – with 25% of their children to be normal and homozygous genotypes (TT), 50% as carriers like the parents (Tt), and the other 25% turn out to be affected (tt). Following Mendel’s Laws, this particular conclusion fits in well with The Law of Independent Assortment as the outcome of a punnett diagram is the same. As above, this equation has worked out to be the same and is therefore a monohybrid cross also.

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Having a woman who is a homozygous tongue-roller and non-PTC taster (TTrr) marry a man who is a heterozygous tongue-roller and a heterozygous PTC taster (TTRR), you come up with the dominant recessive always coming out on top and providing all sixteen children to be tongue-rolling non-PTC tasters (TTrR). This predicament deals with a dihybrid cross – dealing with a cross of first-generation offspring of two individuals who contrast in two characteristics of specific activity.

With an individual being a heterozygous tongue-roller and a heterozygous PTC taster (TTrR), then going and marrying another individual obtaining the exact traits then there is automatically a pattern formed. The outcome is that it is splits into quarters – 25% of the offspring would be heterozygous tongue-rollers but affected homozygous non-PTC tasters (TTrr), 25% would be heterozygous tongue-rollers and heterozygous PTC tasters (TTRr), 25% would be carriers and the same as the parents of heterozygous tongue-rollers and heterozygous PTC tasters (TTrR), and then the final 25% would be homozygous tongue-rollers and homozygous PTC tasters (TTRR). This equation also is classed as a dihybrid cross.


Genetic linkage is the process of when two genes that are found to be close to one another on a chromosome, are frequently rooted together. When they are found to be a lot closer to each other, the chances are higher of them becoming inherited consistently. On the opposite of things, if the genes are found to be further apart from one another but on the same chromosome, then they are more inclined to become detached at the time of genetic recombination (a result of offspring with a mixture of characteristics that contradict with ones found in each of two parents). Overall, the stamina of linkage among the two genes relies on the length and gap between the genes that are on the chromosome. Linkage is done if crossing over it does not happen amid the same time as meiosis, and that recombination in the thick of the genes doesn’t occur on homologous chromosomes. In order to measure out the right amount of linkage that is between that of two genes comes down to approximately calculating the recombination fraction, also seen as ‘r=R/N’.

Controlling the body’s characters are the somatic chromosomes that come from autosomes and what determine the gender of a human (whether it be male or female) all comes down to the allosomes. All autosomes are identical in both sexes but what makes them differ are the allosomes, as they are the ones that create the arrangements of behaviour, form and shape. Amazingly the only difference to a different sex of an individual comes down to just two allosomes, and the rest of the 44 chromosomes per gender are the autosomes. The dissimilar characteristic that changes that between a male and female is a simple, XY (male) and XX (female). Although gender chromosomes are the sources that manage the build-up of sexual characteristics, the autosomes are not precisely associated with the beginning of an organism.

Crossing over, which is formally known as chromosomal crossover, is the swapping of genetic material among the homologous chromosomes that effectively gives a combination of chromosomes. The process of synapsis takes places in one of the last stages of the genetic recombination during prophase I of meiosis and concurrently with prophase I, the homologous chromosomes join to each other and combine as a duo. At the same point that happens, crossing over is occurring by transferring pieces of DNA in the middle of the homologous chromosomes and enabling for self-reliant varieties to take place. A chromosome is created from a shortened chromatin and is an accumulated group of genes that transfer DNA. One half of two identical duplicates of a clone chromosome are known as a chromatid. These two duplicates are linked together during cell division at the centromere (also known as the sister chromatids). These sister chromatids then disconnect in the anaphase stage of mitosis where they then transform and become known as a daughter chromosome.


There are two different variations to show for the features of all species. First off there is continuous variation, where if there is a characteristic of any species that is able to differ regularly over an extent of values. One example of continuous variation is that of human height, when height scopes from the shortest to the tallest but there are different possibilities of height measures that vary in between. A couple of other examples are weight and foot size.

The other variation comes down to discontinuous, where a characteristic of any species has a restricted sum of possible values. One example of discontinuous variation is human blood groups, when there is no other possible answer than that of the four blood groups that exist (A, B, AB, O). With there being no other chance of any other, then this is considered to be discontinuous. A couple of other examples are gender and eye colour.


Mutation is the alteration of a genes format, which may lead entity different to be sent to ensuing creations. This is brought about in a couple of different ways – with a change of single based units in DNA, or because of the cancellation, displacement or insertion of greater portions of genes and chromosomes. The cause of mutation takes place for various reasons. A couple of examples are that DNA is unsuccessfully able to copy correctly, and an external influence is responsible for developing mutations through revealing itself to particular radiation or chemicals that are the main foundation to DNA breaking down.

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De novo mutations are mostly known as being the ‘new mutations’ and found to have two different types: hereditary, and somatic (acquired). This specific mutation is known in some cases to take place inside only the human’s sperm or egg cell and no other. Unfortunately, researchers and scientists say that it is beyond the bounds of possibility to know when a de novo mutation is forming within the human egg or sperm cells. Even though nobody knows when a de novo mutation takes place, it is still known that these mutations may be the explanation to genetic disorders where a child affected with it in every cell of the body, but that child’s parents to not have a trace or any family history to show signs of such disorder. Examples and disorders are hard to come by when it comes to a de novo mutation, as much it may be slightly similar to a mutation, but an example of de novo is autism. This displays the effects of a lower IQ level and more-disabling symptoms to those individuals affected with the condition.

When a human has two or more cell populations with a contrasting composition of genetics, it is known as mosaicism. Mosaicism is a disorder that is brought about because of a mistake in the early stages of growth in an unborn child during cell division. The condition affects various cells in the body, including: blood cells, skin cells, and gamete cells (egg and sperm). With these affects the condition is eligible to cause disorders – mosaic down syndrome, mosaic klinefelter syndrome, and mosaic turner syndrome.

Gene polymorphism is a condition in which the existence of genetic variation takes place inside a population that is conducted by natural selection. There is a slight difference when it comes to the polymorphism condition, and mutation – only a mere 1% cut-off point between them. For an individual to be categorized as obtaining polymorphism, then the least common allele essentially has to have a frequency of 1% or more. Whereas when it comes to an individual retrieving a mutation, the frequency must be lower than 1% in the population. An example of polymorphism is that there could be a small change to just one of the three billion nucleotides found in an individual, and this change could give an individual a bitter taste to cruciferous vegetables e.g. broccoli and cabbage. This bitter taste is known as phenylthiocarbamide and a change in chromosome 7.


Protein synthesis is one of the most fundamental biological processes by which individual cells build their specific proteins. Both DNA and RNA are involved in the process and it is initiated in the cell’s nucleus. In the nucleus is where specific enzymes unwind the needed section of DNA, which makes the DNA accessible in this region and also for a copy of the DNA to be made. ­­

The two main stages of protein synthesis are transcription and translation.

Before the whole process of protein synthesis begins, the equivalent RNA molecule is created by the RNA transcription. A system made by double-stranded molecules of nucleic acid is also known as a double helix. In this case it is a DNA double helix and is used as a guide by the RNA polymerase to combine an mRNA (messenger RNA). The mRNA goes through dissimilar sorts of growth when the destruction of non-coding series takes place, with one growth containing splicing. Splicing is a term for the process of introns being removed from hnRNA so it can create that mRNA that consists of exons. The second stage of protein synthesis comes down to translation, of which is best known for being the real synthesis of protein. The aid of further nucleic acid and protein elements and a larger number of chemical reactions are needed in the translation development. One of the protein elements needed is ribosome, of which supplies its key machinery to help with the course of translation.  


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