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AS and A Level: Genetics, Evolution & Biodiversity

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  1. AP Biology Lab Seven: Genetics of Organisms.Hypothesis In the sex linked cross of Drosophila Melanogaster, a phenotypic ratio of 1:1 will be obtained.

    The larval stage of the Drosophila eats all the time. Larvae tunnel into the culture medium when they eat. The larva will shed its skin as it increases in size. In the last of the three larval stages, the cells of the salivary glands contain giant chromosomes that can be seen under low power in a microscope. The pupal stage. Before a larva becomes a pupa it climbs the side of the container. The last larval covering then becomes harder and darker, forming the pupal case. Through this case the later stages of metamorphosis to an adult fly can be seen.

    • Word count: 2054
  2. Recombinant DNA technology used for insulin production

    The process which is to be followed is named as ?Recombinant DNA Technology?. In order to access the gene that is responsible for the production of insulin in humans, the DNA it is found on, must be extracted from the human cell. This is primarily done by breaking the cell membrane and then the nuclear membrane of the human cell, allowing having direct access to the chromosomes which will actually lead onto identifying the exact location (Gene Mapping) of the human insulin gene on the chromosome.

    • Word count: 773
  3. DNA Fingerprinting process

    containing the insulin gene are being reinserted into the E.coli cells, there is a very low possibility that all the plasmids will be able to make it to the desired location (E.coli cells). How is PCR Done? PCR is a 3 stage cycle; 1. The first stage is the Denaturing of DNA which is carried out at 94-96°C. At this stage, the high temperature breaks up the hydrogen bonds which hold the double stranded DNA together and the strands separate into two single strands.

    • Word count: 969
  4. Sex linkage in fruit flies and huntingdons disease

    It is known that red eye colour (R) is dominant to white eye colour (r). In the P generation red eyed male flies (XRY-) were crossed with white eyed females (XrXr). The outcome of the F1 generation were half male white eyed (XrY-) and half female red eyed (XRXr). These results were obtained because the mothers? genes determine the male offspring?s eye colour; as the mother has both recessive, white eye colour alleles, the male offspring?s are 100% white eyed (XrY-).

    • Word count: 761
  5. Evaluating generations of fruit flies for inherited characteristics.

    (Offspring?s are AA and Aa with long wings) and 25% of them possess recessive alleles (a) for wing size (aa with vestigial wings). The female parent possesses large wings with heterozygous alleles (Aa), the male parent has the same heterozygous alleles (Aa) with large wings that are normal and dominant in fruit flies. The overall inheritance of the offsprings would be 25% homozygous dominant and 50% heterozygous, which would show up as large wings and a 25% will be homozygous recessive, which would show up as vestigial wings, as the F2 generation receives both a dominant allele (A)

    • Word count: 1976
  6. Genetics- Transcription and Translation

    It helps the single RNA nucleotides to match up with the nucleotides on the template DNA strand. This process occurs through complementary base pairing, when Adenine matches Uracil, Thymine with Adenine, Guanine with Cytosine and Cytosine with Guanine. The template strand is complementary to the coding strand and due to this reason the RNA strand is built by using the template strand. This way the exact copy of the coding strand is formed on the mRNA strand, the only difference is Uracil takes the place of Thymine.

    • Word count: 893
  7. Mitosis in Onion Tip cells and Meiosis in Locust Testis Squash Cells

    The spindle fibres hold on to the centromere of the chromosome to accomplish the task of aligning them. In Anaphase the centromeres separate and the spindle fibres shorten in order to pull the sister chromatids to the opposite poles of the cell. Now, there are 46 haploid chromosomes on each pole of the cell. The chromosomes are still in the shape of fat fingers. During Telophase, the spindle fibres break down and disappear, allowing the nuclear membrane to re-appear around the two sets of 46 haploid chromosomes on opposite poles of the cell. The nucleolus also reforms. The chromosomes become uncoiled (spaghetti-like).

    • Word count: 887
  8. Media reports and the public perceptions about science - MMR scares.

    After watching this people may want to become doctors or do something that is ?life changing? and involves helping other people. A documentary: Japan?s Tsunami: How it happened is a documentary that shows how the tragic tsunami that claimed so many lives, happened. With the use of science it breaks down every point of the massive earthquake measuring 9.0. Public perceptions on science may change as they may want to become Seismologists a person who studies seismic waves like the person shown in the documentary Professor Roger Bilham.

    • Word count: 1890

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