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AS and A Level: Genetics, Evolution & Biodiversity

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  1. Pre-implantation genetic diagnosis

    to increase the chances of an ongoing pregnancy. The main indications for PGS are an advanced maternal age, a history of recurrent miscarriages or repeated unsuccessful implantation. It has also been proposed for patients with obstructive and non-obstructive azoospermia. The Mechanics of PGD PGD is a multi step process involving egg extraction, IVF, cell biopsy, genetic analysis and embryo transfer. First, as in IVF, eggs are fertilized in a lab. The genetic material for testing can be obtained in two ways. The most common method is to use one or two cells take from an embryo two to four days after fertilization.

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  2. case study- cystic fibrosis

    The DNA can then be propagated in a foreign host cell. This biotechnology has been around since the 1970s, and it has become a common practice in molecular biology labs today. Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal. Dolly was created by reproductive cloning technology. In a process called "somatic cell nuclear transfer" (SCNT), genetic material is transferred from the nucleus of a donor adult cell to an egg whose nucleus, (and so its genetic material), has been removed.

    • Word count: 3721
  3. Investigate patterns of inheritance for a single characteristic such as body colour of Drosophila Melanogaster and examine Mendel's laws of dominance and segregation.

    There were 3 vital conclusions taken from these experiments. 1) Inheritance of specific traits is determined by units of inheritance 2) Each parent donates one such unit to its offspring. 3) The trait either shows in the offspring or not. These three conclusions give the basis for two fundamental laws of inheritance and also some fundamental terminology. The units of inheritance are known as genes. Genes exist in pairs of alleles, alternate forms of the same gene i.e. the gene for flower colour can have the purple colour code or the white flower code.

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  4. Outline and Critique the Claim that GeneticTherapy is justified but Genetic Enhancement is not

    First of all, 'gene' is a word obviously used in biology or bioscience to point out the plasma that is believed functioned in human body as a heredity agent. Human Genome Project Information uses this technical term by stating that genes, which are carried on chromosomes, are the basic physical and functional units of heredity. Genes are specific sequences of bases that encode instructions on how to make proteins. Genes could be altered so that the encoded proteins are unable to carry out their normal functions, genetic disorders can happen (www.ornl.gov).

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  5. gm food

    Furthermore, one common example is that people have used selective breeding to develop a strain of low-cholesterol chickens. In other words, selective breeding can be used to develop desirable trait of any living species. Genetic modification is the expansion of the traditional selective breeding, which allows scientists to insert specific beneficial genes into plants or animals, without any unwanted genes. Genetic modification is a much more precise method, which saves a lot of effort of having to go through the process of trial and error.

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    Most restriction enzymes make a staggered cut in the two strands, forming sticky ends. The cut ends are "sticky" because they have short stretches of single-stranded DNA. These sticky ends will stick (or anneal) to another piece of DNA by complementary base pairing, but only if they have both been cut with the same restriction enzyme. Restriction enzymes are highly specific, and will only cut DNA at specific base sequences, 4-8 base pairs long.Restriction enzymes are produced naturally by bacteria as a defence against viruses (they "restrict" viral growth), but they are enormously useful in genetic engineering for cutting DNA at precise places ("molecular scissors").

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  7. Explain how DNA fingerprinting works.

    When DNA is heated to about 80 degrees Celsius, the DNA unzips. Since, the enzyme is extracted from an organism that is adapted to such high temperatures, the enzymes are not destroyed and continue to work. The unzipped, single strands act as templates. Primers designed to base-pair with the ends of the DNA strand will be added. The mixture is cooled to about 30 degrees Celsius and this promotes base-pairing between DNA strand and primers. The DNA polymerase recognizes the primers as Start tags and they assemble complementary sequences on the strands.

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  8. Chromosomes and DNA

    Females have XX sex chromosomes and males have XY. * Two chromosomes of each pair are separated from each other during meiosis. Meiosis is a type of cell division used to make sperms or eggs. * Gametes have single chromosomes not pairs. All eggs have an X. Sperms have either an X or a Y. * X and Y sperms are released during intercourse. Chance plays a part in fertilisation - here the male sex chromosome joins the X chromosome found in an egg.

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  9. What different methods exist for studying genetic variation at a molecular level? How could an allele polymorphism mutation be shown to contribute to a disease/ trait?

    One of the major achievements of the Human Genome Project has been to generate 300,000 of these SNPs with the ultimate goal of creating an SNP map of the entire human genome2. In comparison, simple tandem repeat polymorphs (STRPs) consist of a short DNA sequence that has been repeated many times in tandem at a particular locus in the genome. A STRP with a repeating unit length of 2-9bp is labelled a microsatellite3 (e.g. the repetition of CAG --> CAGCAGCAG in a length of DNA), whereas a repeated unit length of 10-60bp is deemed as a minisatellite or variable number tandem repeat (VNTR).

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  10. GCSE Biology Revision

    Organs are usually connected together to perform a series of processes in the body and make up systems. FOOD: Food is used to: -Oxidise and produce energy -Be incorporated into new cells to produce growth -Renew or replace parts of tissue or body chemicals. A balanced diet is: -a sufficient number of calories or kilojoules to fill energy requirements. -Correct proportions of Proteins (for growth and repair, made of amino acids.), Carbohydrates (main energy source, contain sugars and starch built of glucose), Fats and oils (produce the essential body oils, used to produce body fat for cushioning and insulation), Building blocks, fatty acids and Glycerol.

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  11. Oncogenes are genes that cause cancer.

    Tumor Viruses A virus is little more than a packet of genetic information encased in a protein coat. The information can be embodied in either DNA or RNA (whereas in the cells of higher organisms the genetic archive invariably consists of DNA). Both DNA and RNA are long strands of four of the chemical units called nucleotides. The sequence of the nucleotides constitutes a coded message, punctuated into the discrete units called genes. The instructions encoded in genes are carried out in various ways.

    • Word count: 6160
  12. Genetic Modification

    Unit is to contribute to the understanding of novel muscle-specific genes. Telethonin The MMB Unit is collaborating with the Genome Research Group at CRIBI, University of Padua where an extensive project of discovery and classification of genes expressed in human skeletal muscle has led to the detection of many new muscle genes including those being characterised by the Unit, namely telethonin, ZASP, FATZ and HSPD2860. Any information obtained on the function of these genes will be useful for an overall understanding of muscle behaviour and may also lead to the association of these genes to neuromuscular pathologies.

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  13. Cell Theory - Discuss the theory that living organisms are composed of cells.

    available for transporting materials into/out of the cell. 1.1.10 State that unicellular organisms carry out all the functions of life. Unicellular organisms carry out all the functions of life 1.1.11 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. 1.1.12 Define tissue, organ and organ system. Tissue: a collection of cells that cooperate to perform an action within an organ, eg, nerve cells Organ: a collection of tissues cooperating to perform a specific function for the organism, eg, heart Organ System: a system of organs that cooperate in order to complete metabolic processes for the benefit of the entire organism, eg, digestive system.

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  14. Genetically modified foods have been proven safe but the hysteria surrounding them has been unfounded and highly questionable.

    Born in 1823, a man by the name of Gregor Mendel traced the genetic characteristics of living things. When scientists discovered the DNA that was wrapped up inside all living cells, they gained access to the "blueprints" of almost every living thing on Earth. In 1962, James Watson and Francis Crick solved the mystery of the DNA structure, making the double-helix concept and nucleotide strands become an international piece of knowledge. Thus, they received the Nobel Prize for Medicine. In 1980, the US Supreme Court made a ruling that genetically altered life forms would require patenting.

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  15. You are given a cloned gene from Homo sapiens and are asked to identify structurally similar genes (potential orthologues) in a. Arabidopsis. b. Bombyx mori (silk moth).  How will you determine the expression pattern of the gene?

    This separation is based on conformation. I would use a CsCl density gradient to separate my plasmids from the rest as although it takes longer to perform the yield is much higher and quality of the sample is better. CsCl density gradients work via spinning your sample in an ultracentrifuge. The Caesium and Chlorine molecules in solution are forced downwards but this is counterbalanced by diffusion. What you are left with is a gradient of CsCl with differing densities at different points, see diagram. The sample, which is now in the gradient, separates according to the individual components buoyancy densities.

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  16. A study into the effectiveness of Hydroxycarbamide (Hydroxyurea) in treating the complications caused by Sickle Cell Anaemia and side effects caused by taking the drug:

    This reduces the threat of Crisies? to an affected person. Red blood cells are the body?s principal means of transporting oxygen around the body. Sickle cell anaemia is a genetic blood disorder where red blood cells develop abnormally. These cells are rich in iron containing haemoglobin which bind to oxygen and are responsible for the blood's red colour. In humans, red blood cells are flexible biconcave disks. Sickle cell anaemia however, contains an abnormal type of haemoglobin called ?haemoglobin S?.

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  17. How Does The Oxygenation Level Of The Water Affect The Number Of Stonefly Larvae?

    So factors like velocity of water and amount of plant life in the water can effect how much dissolved oxygen is inside of it. [2] Oxygenation levels must be over a certain concentration for aquatic life to survive, it must not reach too high, as that can be dangerous for the organisms living in the water. A scientific journal I have found during research states that: ?Safe concentrations of dissolved oxygen for survival and adult emergence of larvae of nine species of aquatic insects, including mayflies, stoneflies and caddis flies ranged from 0.6 mg/litre for the midge Tanytarsus dissimilis to slightly less than saturation for the emergence of Ephemera simulans (18.5 C).

    • Word count: 3571

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