Plant Genetics

Genetic coding is ubiquitous to all life forms on Earth

Although there has been a revolution in the biological sciences in the past twenty years, there is still a great deal that remains to be discovered. The completion of the sequencing of the human genome, as well as the genomes of some agriculturally and scientifically important plants for example rice has increased the possibilities of genetic research immeasurably.

Plants differ from animals in a few ways that make the study of plant genetics interesting. Like mitochondria, chloroplasts have their own DNA. Like animals, plants have somatic mutations, but these mutations can contribute to the germ line with ease, since flowers develop at the ends of branches composed of somatic cells. People have known of this for centuries and mutant branches are called sports. If the fruit on the sport is economically desirable, a new cultivar may be obtained.

Some plant species are capable of self-fertilisation and some are nearly exclusively self-fertilisers. This means that a plant can be both parents to its offspring; a rare occurrence in the animals. Scientists attempting to make crosses between different plants must take special measures to prevent the plants from self-fertilising.

Plants are generally more capable of surviving and flourishing, as polyploids. Polyploidy, the presence of extra sets of chromosomes is not usually compatible with life in animals. In plants, polyploid individuals are created frequently by a variety of processes, and once created usually cannot cross back to the parental type. Polyploid individuals, if capable of self-fertilising can give rise to a new genetically distinct lineage, which can be the start of a new species. This is often called instant speciation. Polyploids generally have larger fruit, an economically desirable trait and many human food crops, including wheat, maize, strawberries and tobacco are either accidentally or deliberately created polyploids.

Hybrids between plant species are easy to create by hand-pollination and may be more successful on average than hybrids between animal species. Often tens of thousands of offspring from a single cross are raised and tested to obtain a single individual with desired characteristics. People create hybrids for economic and aesthetic reasons especially with orchids.


Deoxyribonucleic acid or DNA is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, or a code since it contains the instructions needed to construct other components of cells such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes but other DNA sequences have structural purposes or are involved in regulating the use of this genetic information. Plant geneticists use this sequencing of DNA to their advantage as they splice and delete certain genes and regions of the DNA molecule to produce a different or desired genotype and thus, also producing a different phenotype.

Gregor Mendel was an Augustinian priest and scientist, and is often called the father of genetics for his study of the inheritance of certain traits in the Pisum plants. Mendel showed that the inheritance of these traits follows particular laws, which were later named after him. The significance of Mendel's work was not recognized until the turn of the 20th century. Its rediscovery prompted the foundation of the discipline of genetics allows geneticists today to accurately predict the outcome of such crosses and in determining the phenotypical affects of the crosses. He was born on 20 July 1822 and died on 6 January 1884 from chronic nephritis.

Genetically modifying crops

Next, the two separate cut-up DNA sequences are introduced into the same container, where the sticky ends allow them to fuse, thus forming a ring of DNA with additional content. New enzymes are added to help cement the new linkages and the culture is then separated by molecular weight. Those molecules that weigh the most have successfully incorporated the new DNA and they are to be preserved.

The second method of genetic engineering is called the vector method. It is similar to the plasmid method, but its products are inserted directly into the genome via a viral vector. The preliminary steps are almost exactly the same: cut the viral DNA and the DNA to be inserted with the same enzyme to combine the two DNA sequences and separate those that fuse successfully. The only major difference is that portions of the viral DNA, such as those that cause its virulence, must first be removed or the organism to be re-engineered would become ill. This does yield an advantage - removal of large portions of the viral genome allows additional space in which to insert new genes.

The biolistic method is also known as the gene-gun method. It is a technique that is most commonly used in engineering plants - for example, when trying to add pesticide resistance to a crop. In this technique, pellets of metal (usually tungsten) coated with the desirable DNA are fired at plant cells. Those cells that take up the DNA again, this is confirmed with a marker gene are then allowed to grow into new plants, and may also be cloned to produce more genetically identical crop. Though this technique has less finesse than the others, it has proven quite effective in plant engineering.


The use of genetically engineered crops has helped many farmers deal with pest problems that reduce their crop production. The impact of pest-resistant crops has led to a much higher yield for agriculturists in today's world. They can use less pesticides which reduces the chemicals that they put into the ground. Certain engineered crops such as “Roundup Ready Corn”, a patented transgenic maize variety has led to farmers all over the world and in the US to increase crop yield exponentially in recent years. Agriculturists can use an herbicide to kill weeds, yet the genetically engineered corn is resistant to the herbicide and is left unaffected. Thus, fields are produced that are virtually weed free. Genetically engineered crops can also benefit farmers when dealing with potentially harmful viruses and bacteria. Scientists found a virus resistant strain of maize in the highlands of Mexico and extracted the part of the maize's genome that coded for resistance against the virus and incorporated it into their existing strain of commercial corn. This allowed the commercial strain to produce progeny that were resistant to the virus. Thus, the crops were saved from decimation.


According to Vaughan A. Hilder and Donald Boulter at the Department of Biological Sciences, University of Durham, there have been serious failures in resistance to targeted pests in Bt cotton; most plant-derived resistance factors produce chronic rather than acute effects; and many serious pests are simply not susceptible to known resistance factors. According to John E. Berringer the outcome of releasing genetically modified organisms into the environment is still not known.

Genetically Modified Foods and the Implement of Genetic Engineering

Throughout the advancing technology of today, the human culture is becoming futuristic with science and all of its components. Genetically modifying foods presents positive opportunities in agriculture and human health. Furthermore, more scientifically advanced modifications that select genetically superior plants, have enhanced the yield of crops, improved storability, and increased disease resistance. To simply remove genes from one organism and transfer them to another is generally harmless if we take appropriate precautions. This often debated issue holds many objections. Moreover, one may claim that modifying genes at all is unnatural and evaluates a sufficient risk to many different organisms and species. However, the current technology we possess provides us with the capabilities to go beyond our limits. Why draw the line here?

Genetically modifying foods presents positive and beneficial opportunities. In most cases, we are not eating those genes. By the time a genetically engineered corn plant has been processed into corn oil, virtually none of the genes or the proteins they produce are left in the food (Nutrition Action Health letter, 2001). Transferring genes from one plant or animal to another provides an advantageous outcome to this production. A better resistance to weeds, pests, and diseases is produced as well as better yield and a more efficient use of land. Additionally, altering genetics in foods contributes to a better texture, flavour, and nutritional value of a product. Therefore, there is a longer shelf life and less herbicide or other chemicals are used in the production of genetically modified foods, which provides a healthier option and an increased selection for the consumer.

Biotechnology is going to help solve problems that we face going into the next century such as reduction of allergies, development of more nutritious foods, and an increased nutritional production to feed a growing population (McLaughlin, 1999). Subsequently, changing one or two genes does not make a foodstuff unacceptable. Religious and vegetarian groups would object to genes from some species, while adequate protection can be given with labelling the product. Ethically, one may argue that it is radically useless to modify foods genetically or that agriculture is already too technological and it will only progress more negatively. However, it is likely that increasing numbers of genetically modified foods will emerge in the near future with more variety of modifications and associated benefits.

Generally, genetically modified foods will affect the lives of most people in the areas of food, medicine and environmental protection as it meets the modern technology of today. This advancing technology requires careful regulations to ensure that there is no threat to human health in introducing this production system. Adequate labelling, accurate product information, and the provision of species are some of the measures that one can review as a means of ensuring public confidence in the safety of genetically modified foods. Additionally, this is also effective as a means of providing those with objections to the technology with a means of avoiding these foods. Fundamentally, by altering the genes of a specie for the benefit of human race and its development is simply not “changing” the rules in life, but more rather it allows us to progress into a new revolution of advancements for the future.

Eleven years ago, genetically engineered bacteria, which unexpectedly killed beneficial soil fungi, escaped into sewers through human error and have become toxic to plants and survived when expected not to. These are the sorts of consequences that come with playing God. DNA (deoxyribonucleic acid) - the chemical compound that makes up the genes and determines the type of proteins a cell can make - is the core of genetic engineering. There are so many questions that each person must ask each other before making any sort of decision that would affect the future of genetic engineering towards humans. The risks of DNA combinations can be enormous and unexpected such as the formation of bacteria resistant to antibiotics, linkage of DNA molecules with tumour-causing viruses and the introduction of toxin-formation or antibiotic resistant genes. Thus all risks must be taken into consideration. Genetic engineering has already been demonstrated in cattle and studies have shown linkage of DNA molecules with ulcers, cancer and heart disease. Unfortunately, regulation of biochemical research ethics has been erratic and half-hearted for years. The United States allowed its only national bioethics commission to expire in 1989. 2 As for in-vitro research, the Reagan Administration cancelled federal funding a decade ago. 2 So work in this area has been privately funded and unregulated disallowing any prevention of experiments and research of highly debated subjects, such as cloning.

Reports on genetic engineering show that scientists and reporters rarely reveal the powerful dangers at present. It just shows that some regulation is desperately needed. Even if it only limits the media and other publications. People need to know the truth and the whole truth and nothing but the truth, which includes both sides, good and bad, and in this case, especially the bad.

Too many people, it is also a moral or ethical consideration. Many people feel strongly that it is not for us to decide what each person is going to look and act like. To them, the idea of playing god is an outrageous sin. If we look at this picture and understand the concept behind The Angel weaving our genes to create us,2 we see the importance of listening to other people and their beliefs. When there are stands against genetic engineering from these people we must listen to them also and not cast them away as just religious fanatics. Not only does gene shopping create a greater similarity among people, but it leaves the door open for total annihilation of the species. When there are a great load of people with similar make-ups, the threat of disease increases. If one person gets a disease, all those similar to him/her will be vulnerable to the disease as well. Immune systems are not able to combat the viruses and bacteria because there is no variety.

DNA strands are just too delicate and complex. The idea of that we can fully understand and map every part of the strand can not be realistic. There will always be holes, therefore making holes in our practices. In the words of Dr. Elena Gates, an expert in reproductive issues at the University of California at San Francisco, "I would not like to announce that Mrs. Jones just gave birth to twins - and she's got two more in the freezer." Many say that genetic engineering can benefit us all, but are they willing to reveal the possibility of almost complete destruction of the human race.

Summary of Morphology

  • Morphology – during juvenile growth they change into a different shape and size. This is very common throughout ivy. The original plant was a shrub with long rounded leaves, now ivies grow up a wall or a fence quickly by aerial roots and oval shaped leaves. This can be prevented by applying gibberellin to juvenile growth.

  • Ivy – juvenile growth is a stereotypical appearance however the mature growth is long, large oval shaped with the flowers. Cuttings taken from horizontally branches have a prostate habitation.

  • Topophysis – prostate habit growth of cuttings.

  • Root capacity – juvenile plants have adventitious roots while adult phase rooting ability is usually diminished considerably and sometimes lost.

  • In some coniferous and deciduous trees are known to be difficult to root.

  • Young juvenile roots – are very easily formed by roots.

  • In one species of eucalyptus there is a relationship between the decrease in rooting ability and the increase with age with a natural root inhibitor.

  • Stooling – repeated cutting back of the parent plant.

  • Etiolation – this method is effective in increasing the production of adventurous roots in stem tissue. This is micro-propagation in the complete darkness. Experiments showed that since 1864 this was a highly effective method.

A help guide to genetics and the possibilities of genetic engineering

  • Gregory Mendel studied inheritance in common garden peas. He established the fundamentals of genetics in the 1850s. He only discovered the changes from parent to offspring. He worked in Austria in a monetary.

  • DNA – deoxyribonucleic acid

  • RNA – ribonucleic acid

  • Both RNA and DNA are genetic codes which hold information about the plants. RNA reads DNA base genes.

  • DNA is made up of 4 chemical building blocks called bases. Each base has two parts, a glucose component which is the same in all four bases linked to a nucleotide. There are four nucleotides in DNA monocles giving the four different bases. The initial letters are (A) adenine, (C) cytosine, (G) guanine and (T) thymine are commonly used to identify the bases. The glucose components link each base together. The bases form into strings of tremendous length, reflecting the large quality of information they store. DNA is in a double helix shape and if unravelled it would reach 1.7 metres long containing about 10,000 genes.

  • A simple three letter code is called a codon which represent amino acids. A protein consists of a string of amino acids anything from about 100 to several hundred. There are 20 naturally occurring amino acids which are presented by a least one distinct codons. There are several amino acid methionine which identifies the start of a gene and there several codons that can mark the end of a gene.

  • Tell plant cells – contained in the RNA like a second wave of genes which help to read. It can also switch on and off cells.

  • Regulatory or control sequences – control overall DNA and help to sort the genetic information and regulates how much a plant cell reads the genes.

  • Protein coding sequences – create bases like writing down information.

  • DNA is read by a cluster of enzymes that physically move along the DNA strand, and under the direction of the regulatory sequences make copies of RNA. This copying process is called transcription. As RNA and DNA function in the same way making multiple identical copies if the genes.

  • These new copies distribute to another type of enzyme cluster, which reads the RNA. Recognises each group of 3 nucleotides and matches to the appropriate amino acid to each codon. These enzymes are translating the genetic codes into proteins. Not all DNA creates proteins; some even create some of the key chemical components in the transcription/translation apparatus.

  • Transcription factors in regulation

  • They copy RNA and DNA prior to protein synthesis

  • They produce flowers in K C A and G. (Look in Flower Formulae).

  • Copies of genomes are called haploids.

  • Polyidisation resulting in multiple copies of genomes in plants. Some chemicals can induce polypoids which increase cell division.

  • Triploids – three copies of genomes.

  • Hexapliods – six copies of genomes.

  • Colchicines – a naturally occurring toxic compound found it autumn crocus is used to induce polypoids. Some breeders have used polyploidisation to try to produce new varieties. Polypoids are usually associated with large flowers and later flowering. Many cultivated plants contain polypoids such as potatoes, daffodils and cyclamen.

  • Most plant cells contain two copies of genomes. In developing flowers, buds, eggs and pollen. Forming gametes or germ cells. These cells go through meiosis this ensures that only one (genome) copy is passed on to the daughter cells.

  • A fertilised egg with pollen is called zygote, which contains two copies of the genomes. The fertilised egg undergoes mitosis the moist common cell division.

  • Meiosis has a second function that ensure that both parent genomes mix their information before gamete formation is called recombination. In new plant cells the parent chromosomes split and join with the opposite kind and mix to become a new DNA strand.

  • The active and inactive forms of genes are called allelic. Trait controlled by the two alleles is called allelic variation.

  • Gardeners know mutation as sports. It occurs when errors happen in the copying process in DNA. They maybe induce by natural or artificial radiation. Viruses and or transposable elements.

  • In the 1960s and 1970s the groundbreaking work of Barbara McLintock on unstable genetic traits in maize lead to the understanding of transposons. They are naturally occurring fragments of DNA that are able to move around the genome by cutting themselves out of DNA and in again elsewhere. Encoding a few genes they are special sequence of the base at each end. They have influences on flower colours, which make variegation such as strips and stops.

  • Hetero and homozygosity – plant cells contain two copies of gemones, cross species are not included. These genes will be the same, controlling the same characteristics and in the same location long the DNA. Most are inbred.

  • Genetic locus – where the alleles are present at each location in DNA.

  • Plants in which two gemones carry identical alleles at all gene louci are described as homozygoisous (homo meaning the same).

  • F1 plants are all the same.

  • F2 inherit most genes from their grandparents.

  • Dominate alleles – they mask the recessive alleles, these control the main genes.

  • Recessive alleles – these types of genes come back every other generation, for example grandparent’s genes to grand children’s. Allele relationships are not that straight forward and can be complex.

  • Genotype – a main controller in appearances from plant genes, phenotype main contributors to flowers.

  • Heterozygous species tend to be perennials.

  • Inbreeding may lead to loss of vigour, size and fertility.

  • Homozygous species are in breeders, they are adapted to self pollination which are highly adaptive.

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