Friday, 12 June 2015

Gross and microscopic structure of skeletal muscle. The ultrastructure of a myofibril. The roles of actin, myosin, calcium ions and ATP in myofibril contraction. The roles of calcium ions and tropomyosin in the cycle of actinomyosin bridge formation.

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The roles of actin, myosin, calcium ions and ATP in myofibril contraction. The roles of calcium ions and tropomyosin in the cycle of actinom...

An organism’s genome contains many repetitive, non-coding base sequences. The probability of two individuals having the same repetitive sequences is very low. The technique of genetic fingerprinting in analysing DNA fragments, that have been cloned by PCR, and its use in determining genetic relationships and in determining the genetic variability within a population. Candidates should be able to - explain the biological principles that underpin genetic fingerprinting techniques - interpret data showing the results of gel electrophoresis to seperate DNA fragments - explain why scientists might use genetic fingerprints in the field of forensic science, medical diagnosis, animal and plant breeding.

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Introns (parts of DNA that don't code for anything) are made up of repeating units called core sequences. Because every individual (apa...
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Wednesday, 10 June 2015

The use of labelled DNA probes and DNA hybridisation to locate specific genes. Once located, the base sequence of a gene can be determined by • restriction mapping • DNA sequencing. Many human diseases result from mutated genes or from genes that are useful in one context but not in another, e.g. sickle cell anaemia. DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes. The use of this information in genetic counselling, e.g. for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment for cancers. Candidates should understand the principles of these methods. They should be aware that methods are continuously updated and automated.

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DNA hybridisation We need to find genes that are causing problems so that we can alter them. This is done by DNA hybridisation: DNA probe i...
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Tuesday, 9 June 2015

The use of gene therapy to supplement defective genes. Candidates should be able to evaluate the effectiveness of gene therapy.

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Gene therapy is when a gene that is missing or not functioning is replaced by one that is. There are two points at which gene therapy can...
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Fragments of DNA can be produced by • conversion of mRNA to cDNA, using reverse transcriptase • cutting DNA at specific, palindromic recognition sequences using restriction endonucleases • the polymerse chain reaction (PCR). Fragments of DNA produced by any of the above methods can be used to clone genes by in vivo and in vitro techniques. In vivo cloning. The use of restriction endonucleases and ligases to insert a gene into vectors, which are then transferred into host cells. The identification and growth of transformed host cells to clone the desired DNA fragments. The importance of “sticky ends”. In vitro cloning. The use of the polymerase chain reaction (PCR) to clone directly. The relative advantages of in vivo and in vitro cloning. The use of recombinant DNA technology to produce transformed organisms that benefit humans. Candidates should be able to • interpret information relating to the use of recombinant DNA technology • evaluate the ethical, moral and social issues associated with the use of recombinant technology in agriculture, in industry and in medicine • balance the humanitarian aspects of recombinant DNA technology with the opposition from environmentalists and anti-globalisation activists.

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Genes are often cloned in order to produce proteins, these can be used to treat diseases. This is better than taking already made proteins b...
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Transcription of target genes is stimulated only when specific transcriptional factors move from the cytoplasm into the nucleus. The effect of oestrogen on gene transcription. Small interfering RNA (siRNA) aws a short, double-strand of RNA that interferes with the expression of a specific gene. Candidates should be able to - interpret data provided from investigations into gene expression - interpret information relating to the use of oncogense and tumor surpressor genes in the prevention, treatment and cure of cancer - evaluate the effect on diagnosis and treatement of disorders caused by hereditary mutations and those caused by acquired mutations.

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Transcription factors are proteins that bind to a section of DNA to start the process of transcription there. There are specific transcripti...
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Totipotent cells are cells that can mature into any body cell. During development, totipotent cells translate only part of their DNA, resulting in cell specialistation. In mature plants, many cells are totipotent. They have the ability to develop in vitro into whole plants or into plant organs when given the correct conditions. Totipotent cells occur only for a limited time in mammalian embryos. Multipotent cells are found in mature mammals. They can devide to form only a limited number of different cell types. Totipotend and multipotent stem cells can be used in treating some genetic disorders. Candidates should be able to - interpret data relating to tissue culture of plants from samples of totipotent cells - evaluate the use of stem cells in treating human disorders.

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All cells in an organism have the same DNA. However, different cells use different parts of the DNA, for example beta cells in the pancreas ...