Genetics+The+Code+Broken

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9.7 Option — Genetics: The Code Broken?
Contextual Outline Science has come a long way since Mendel’s important work on identifying the transmission of inherited factors across generations. The code for transmitting this genetic information has been identified and models have been developed to explain gene functioning. Transcription of the information into functional proteins is now well understood and models are being developed to test how genes direct the structure, function and development of an organism. Modern genetics is moving towards an increased understanding of the biochemical role of individual genes. This is being enhanced by the Human Genome Project that has sequenced the entire human genome to identify all the encoded genes. This module increases students’ understanding of the nature, practice, applications and uses of biology, the implications of biology for society and the environment, and current issues, research and developments in biology.

1. The structure of a gene provides the code for a polypeptide //Presumed knowledge: BOL//
 * Outcome 1:**
 * //protein synthesis and DNA replication//
 * //understanding of models used in Biology//


 * Outcome 4 some more notes**:

Recombinant DNA technology can be used to identify the position of a gene on a chromosome. The protein product of a gene is analysed to determine the amino acid sequence, and consequently to determine the DNA sequence. A complementary DNA sequence is prepared using radioactive materials, which forms the radioactive probe. This single-stranded radioactive probe is then released, and will bind to the gene on the chromosome. Where it binds can be tracked due to its radioactivity, and thus identify the position of the gene on the chromosome.
 * 4.2.4 explain how the use of recombinant DNA technology can identify the position of a gene on a chromosome **

The Human Genome project could not utilised linkage maps, as linkage maps are determined by studying the percentage chances of linked genes staying together during crossing over. Thus it does not give an accurate position of the genes on a chromosome. Various segments of DNA vary largely, with overlaps and repeats, thus the process of identifying the position of genes is too complex to be achieved by studying linkage maps. Linkage maps also do not provide detailed base sequences.
 * 4.3.1 process information from secondary sources to assess the reasons why the Human Genome Project could not be achieved by studying linkage maps **

//Presumed knowledge- how are the harmful genes identified?// 1. Describe current use of gene therapy for an identified disease. 2. Process and analyse information from secondary sources to identify a current use of gene therapy to mange a genetic disease,a named form of cancer or AIDS
 * Outcome 5:** Gene therapy is possible once the genes responsible for harmful conditions are identified.

//Presumed knowledge//-//BOL mutations in DNA may lead to the generation of new alleles.// 5. Process and analyse information from secondary sources to describe the effect of one named and described genetic mutation on human health.
 * Outcome 6**: Mechanisms of genetic change.

**Cystic fibrosis**
Your report should have the following headings:

Background : This should include:
 * SBH 1.2 Outline how the function of genes assist in the maintenance of health
 * SBH 6.4 Present information about the occurrence, symptoms, cause, treatment and management of a named non infectious disease.
 * BOL 4.2 and 4.3 How DNA controls the production of polypeptides and the relationship between polypeptides and proteins
 * BOL 4.4 Explain how mutations in DNA may lead to the generation of new alleles.
 * BOL 4.10 Changes in DNA sequences can lead to changes in cell, activity.

Mechanisms of genetic change: This should include: CB: 6.5 Describe the effect of one named and described genetic mutation on human health using cystic fibrosis as your example,

Gene Therapy :

Gene expression

media type="youtube" key="OEWOZS_JTgk?fs=1" height="385" width="480" Polygenic inheritance media type="youtube" key="gouqTq5p168?fs=1" height="385" width="640"

Dihybrid crosses

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Something to think about

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How to sequence a genome: http://www.genome.gov/25019885 1. Describe what is meant by gene cloning. 2. Briefly review for BOL the processes involved in whole organism cloning and gene cloning. 3. Discuss the protein insulin as an example of gene cloning. 4. Distinguish between gene and whole organism cloning in terms of processes and the products.
 * Outcome 7 Cloning and selective breeding:**
 * Questions due Monday**
 * || **Processes** || **Products** ||
 * **gene cloning** ||  ||   ||
 * **whole organism** ||  ||   ||

5. Read p47 and 48 and do Questions 1-4 on page 48. You have other sources from this page and biotechnology online (CB websites) to help you. 6. Discuss a use of cloning in animals that has possible benefits to humans. Scientists hope that one day therapeutic cloning can be used to generate tissues and organs for transplants. To do this, DNA would be extracted from the person in need of a transplant and inserted into an enucleated egg. After the egg containing the patient's DNA starts to divide, embryonic stem cells that can be transformed into any type of tissue would be harvested. The stem cells would be used to generate an organ or tissue that is a genetic match to the recipient. In theory, the cloned organ could then be transplanted into the patient without the risk of tissue rejection. If organs could be generated from cloned human embryos, the need for organ donation could be significantly reduced. GCB selective breeding

http://www.actionbioscience.org/biotech/mcgee.html Gene cloning

HGP page 13-16 Cloning p24....

media type="custom" key="6821591" =Dolly the sheep dies young= Dolly the sheep, the first mammal to be cloned from an adult cell, was put down on Friday afternoon, after developing a progressive lung disease. Dolly's birth six-and-a-half years' ago caused a sensation around the world. But as many sheep live to twice this age, her death will refuel the intense debate over the health and life expectancy of cloned animals. The type of lung disease Dolly developed is most common in older sheep. And in January 2002, it was revealed that Dolly had developed arthritis prematurely. She was cloned using a cell taken from a healthy six-year-old sheep, and was born on 5 July 1996 at the Roslin Institute, Edinburgh, Scotland. The Institute's Harry Griffin says: "Sheep can live to 11 or 12 years of age. A full post mortem is being conducted and we will report any significant findings". Following the post mortem, Dolly will be donated to the National Museum of Scotland in Edinburgh, where she will be stuffed and put on display.
 * 17:56 14 February 2003 by [|**Will Knight New Scientist**]

Short telomeres
Some cloned mammals, including Dolly, have shorter telomeres than other animals of the same age. Telomeres are pieces of DNA that protect the ends of chromosomes. They shorten as cells divide and are therefore considered a measure of ageing in cells. The only study of cloned mammals that have lived long enough to determine any effect on lifespan revealed that the mice involved died prematurely. The research was conducted at the National Institute of Infectious Diseases in Tokyo, Japan, and published in February 2002. Other cloned animals appear normal and healthy, for example the 24 calf clones created by US cloning company Advanced Cell Technology, but these have yet to live long enough to draw any conclusions. On 2 February 2003, Australia's first cloned sheep died unexpectedly at the age of two years and 10 months. The cause of death is unknown and the carcass was quickly cremated, as it was decomposing.


 * Outcome 8:**

Question 1: What role do genes play in embryonic development? Biology in Context-Spectrum of Life p564 3rd edition One of the reasons that scientists are so interested in the expression of genes is that determining what controls gene expression helps us understand what it is to be human. The difference in gene arrangements between primates and mammals is very small.The difference between the sequence in a chimpanzee and human is only about 1-2%. But clearly it is not just the sequence of genes that determines its features. The sequences that control the way genes are switched on and off and the way genes influence each other must play an important role. The differences in DNA sequence may be tiny, but as each organism develops from an embryo, thousands of tiny differences in the way DNA is activated accumulate to produce a very different organism.
 * Identify the role of genes in embryonic development p51**
 * On fertilisation, two haploid sets of chromosomes join to produce a zygote containing all the genes necessary to grow into a new individual.Every aspect of the the development of the organism is directed by its genes.
 * As mitosis occurs, the resulting embryo grows into a mass of undifferentiated cells. As the embryo develops, cells differentiate and become specialised in their size, shape and function according to which genes are used to regulate these developments. Some cells form the circulatory system while others develop into a network of nerves. Within specialised cells, different genes are switched on. This results in the production of different proteins and enzymes which, in turn, alter the cells metabolism and structure.
 * The activities of genes are regulated by other genes to control all cell activities, production of proteins and enzymes, at different times of development. A variety of proteins, activators and repressors, link up with different parts of DNA to cause interaction between various other proteins and genes. The result is that some genes are affected and expressed and others are repressed or inhibited. Genes are turned on or off according to their position in the embryo, function and age of the developing embryo/foetus/individual. Chemicals which may diffuse into cells from neighbouring cells alter the expression of genes.
 * During embryonic development, the genes for cellular respiration are active in all cells. Hence these genes are switched, expressed, in all cells.
 * Review Outcome 1 gene expression. The process by which genes are turned on an off is not fully understood and this is an active filed of research.
 * Summarise the role of gene cascades determining limb formation in birds and mammals p51-52**
 * http://bcs.whfreeman.com/thelifewire/content/chp19/1902003.html (Gene cascades in drosophila)**
 * The development of parts of your body, such as arms and legs**,** is not controlled by a single gene. Many genes must be switched on and off in the appropriate sequence to form muscles,blood vessels, nerves and various tissues in the correct arrangement in your limb.
 * During limb development in birds and mammals, an appropriate sequence of genes is turned on to form such things as bones, muscles, ligaments, tendons, nerves and blood vessels. As each gene is turned on, certain substances are produced that turn on the next gene in the sequence. This process is repeated and continues as the limb develops. //This process of a sequence of genes being turned on which then causes other genes to be turned on is called a gene cascade.//
 * The CSIRO is currently studying the development of limbs in chickens. During embryonic development, cells that form limbs are specifically programmed to form either a leg or a wing. At this stage, scientists know about gene sequences after the cells are programmed to form a part of the body such as a leg, but they do not know very much about the gene cascade in the preprogrammed stage of development. They do not know the particular chemicals that will determine which cells will form a limb in the first place.
 * Question 2: What is meant by cascading genes? Illustrate your answer with an example..
 * Identify data sources, gather, process and analyse information from secondary sources and use available evidence to assess the evidence that analysis of genes provides for evolutionary relationships**
 * **Identify** data sources such as the Internet, biology text books and science journals.
 * **Gather information** from the identified sources.
 * **Process the information** by assessing the reliability of information from various sources. If two have different information cross check them from one or two other sources.
 * **Analyse information** you have gathered and processed to make generalisations about evolutionary relationships identified by gene analysis. p54
 * **Use the available evidence** to assess the evolutionary relationships that gene analysis has provided.

Evidence from biochemistry and molecular biology shows that all cells contain similar amino acids, nucleotides, sugars and fatty acids. Chemical processes such as protein synthesis within cells are also similar. Palaeontology and comparative embryology have revealed similar processes involving homologue genes in the development of the bones of the head, dentition, brain and limbs. Genes for repairing DNA are similar in all eukaryotic organisms. Photosynthesis, like all chemical reactions is controlled by a protein found in chloroplasts. This protein is similar in all plant species as well as some cyanobacteria.
 * Describe the evidence which indicates the presence of ancestral vertebrate homologues in lower animal classes p52**
 * In BOL you learnt about homologous structures providing evidence for evolution.One of these structures was the forelimb of vertebrates- the pentadactyl limbs in vertebrates provide evidence for evolution from common ancestors. Recent studies in molecular biology have uncovered DNA sequences that are similar in many organisms. These DNA sequences are called homologue genes eg homeotic genes, homeobox or Hox genes. These genes regulate the development of an organism by producing proteins that switch other genes on and off. Homeotic genes were discovered in Drosophila and all contained a similar region of 180 base pairs - called Homeobox. They soon found homeobox genes in Mice and other mammals, where they are referred to as Hox genes.
 * What makes these homologue genes so remarkable is that the similarities exist among many eukaryotes, which are vastly separated on the evolutionary scale.
 * An example of a homologue is the gene cascade for skeletal and neurological development in limbs. It is similar in organisms such as humans, chickens, rodents, insects, nematodes and molluscs. Experiments have confirmed that the homologue gene from an amphibian can regulate the corresponding gene in mammals. A mammal homologue gene can regulate the corresponding gene in insects such as fruit flies.
 * These homologue genes exist in many eukaryotic organisms, both vertebrates and invertebrates as well as some fungi and plants. This suggests common ancestry between all eukaryotic organisms.see diagram p53
 * Some of the best understood homologue genes are hedgehog genes-so called because a mutation in the hedgehog gene causes the protein it produces to have a spiky appearance. The sonic hedgehog gene is active in the limb development of flies, mice, chicken and other animals and is one of the essential genes in the gene cascade of limb development.
 * Question 3: What are gene homologues? How doe they provide evidence for evolution among eucaryotes?
 * Additional information**
 * Discuss the evidence available from current research about the evolution of genes and their actions p54**
 * .In BOL you looked at amino acid sequences as evidence of evolution (cytochrome C and haemoglobin are examples). DNA sequencing is now replacing amino acid sequencing as the technology becomes cheaper and easier. It is also more direct evidence of evolution as it studies the material of inheritance.
 * The study of DNA sequences provides evidence for the evolution of genes. Sequences of bases in genes that do not change or change very slowly over time are used to measure relationships between groups of organisms. For example, in mice, the gene for the development of eyes is similar to the gene in insects.
 * Previously, amino acid sequences in proteins such as haemoglobin, have been used to determine evolutionary relationships. The protein myoglobin in insects provides oxygen to cells and is very similar to a protein with a similar function in primitive fish. Studies of all of these proteins responsible for carrying oxygen suggest an evolutionary pattern for their development. The analysis of the DNA that makes up the genes that code for proteins has provided more evidence of evolutionary changes in certain groups of organisms.
 * Homologues, homeotic or Hox genes are found in most or all groups of multicellular animals and show similar DNA sequences suggesting that these genes evolved in a common ancestor. These genes, being similar in both structure and function, are expressed in similar sequences on chromosomes.
 * The study of mutations of homeotic genes shows that a small mutation can suddenly affect an organism as a gene cascade is altered. A mutation in a homeotic gene can cause one part of the body to develop into another. For example, in //Drosophila// fruit flies, one mutation in a homologue gene can result in legs growing on the head rather than antennae. In humans, a mutation in a homeotic gene for the development of the bones of the skull results in rigidity in the joints between these bones. This can result in abnormal brain growth and possible mental retardation. The base sequence for this gene is very similar in many animals.
 * These gene changes can then result in often dramatic alterations in organisms which may then lead to the rapid evolution of new body structures. This is evidence for the expansion of diversity of living things and the theory of punctuated evolution.
 * Question 4: Use an example to show how DNA sequencing provides evidence of evolution
 * Question 5: .Is amino acid sequencing of Haemoglobin the same as DNA sequencing for haemoglobin. Explain?