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Ganetics, Inheritance and Cells.

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Inheritance Cells New cells are needed for- 1. Growth- as an organism grows it needs more cells 2. Repair- cells become damaged due to wear and tear 3. Replacement- cells wear out and die so each cell has to be able to make copies of itself. The instructions for doing this are contained in the chromosomes within the nucleus of each cell Each characteristic has it's own set of instructions called a gene These are found in the chromosomes In humans each cell has 46 chromosomes (23 pairs one of each pair coming from each parent) Mitosis Mitosis In this process exact copies of each cell are made This process happens all the time and is used for growth, repair and asexual reproduction in which the offspring are identical to the parent Stages of mitosis 1. The cell makes copies of all the chromosomes 2. The cell then divides into 2 each having one set of chromosomes. Skin is an example of a tissue that needs to be constantly doing this Each cell then can only make copies of itself ie skin cells only make skin cells and muscle cells only make muscle cells ...read more.


contain all the eggs for the rest of their lives In boys it doesn't start until after puberty Each gamete will contain a slightly different combination of chromosomes and they also exchange some material during meiosis, which means each sperm, and egg will be different. Fertilisation During fertilisation the 2 sex cells containing half the numer of chromosomes ie 1 instead of 1 pair join and produce a new cell with a complete set of chromosomes and this cell is different to each of the parents This new cell will then start to divide by mitosis to produce a new unique individual Variation Asexual reproduction uses mitosis and produces genetically identical copies of the parent In sexual reproduction the gametes are produced by meiosis this introduces variation as each gamete is different. The combination of genes when the gametes fuse introduces more variety. Cells made in this way contain pairs of chromosomes but 1 of each of the pairs comes from different parents and so they have 1 gene for each characteristic from each parent (alleles) ...read more.


or recessive (ie you need to copies of the gene to have the characteristic) If you carry 1 of each type of the genes for a recessive disease then you are a carrier Genetics Using punnet squares to determine genotypes Some characteristics are coded for by 1 set of genes ie dimples or attached ear lobes Genetic diseases These are not contagious but are caused by faulty genes being passed on from parents to offspring Examples are Huntingtons disease ( a disease of the nervous system) which is caused by a dominant allele and appears between 30-50 years old. There are no cures or treatments. Cystic fibrosis which affects the lungs, pancreas and reproductive system and is caused by a recessive allele. Sufferers produce to much thick sticky mucus which clogs up the lungs and leads to infections. There is no cure but treatment includes physiotherapy to reduce the mucus and enzyme treatment to reduce and thin the mucus. Huntingtons disease Cystic Fibrosis C= Normal c= Cystic fibrosis Curing genetic diseases Scientists hope to be able to replace faulty genes in the future to cure these diseases At the moment genetic screening can be done to identify the risks of a baby acquiring a faulty gene ...read more.

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Response to the question

The candidate has written a detailed report on genetic inheritance and cell mitosis, and included examples of genetic inheritance of certain characteristics, and how they may be caused depending on whether their parents were homozygous of heterozygous for that particular ...

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Response to the question

The candidate has written a detailed report on genetic inheritance and cell mitosis, and included examples of genetic inheritance of certain characteristics, and how they may be caused depending on whether their parents were homozygous of heterozygous for that particular trait, particularly focussing on generically inherited diseases. They have included good descriptions of cell division and replication, including the mitosis and meiosis processes. They have mentioned genetic inheritance in plants, as well as comparing the undifferentiated plant cells to animal cells, which are differentiated from birth. However, they have rarely referred directly back to the question - for example adding 'this increases genetic variation in species' after some sentences, which would help to pull the report together.

Level of analysis

They have discussed genetic inheritance in detail, and explained about dominant and recessive genes, and the probabilities of a child having a particular characteristic given their parents' genes are also described in detail. However, they have not mentioned key topic within genetic variation - for example Darwin's theory of evolution (although Mendal's theories are described briefly) and the effects of mutations (these are not always pathogenic, and cause new genes to be introduces to a population). They have also failed to take opportunities to develop their analysis further by discussing the impacts of some technology (for example the ability for parents to test their genes to discover if their child is likely to suffer from a genetic disorder) on society, and the moral conflicts surrounding them - they have only briefly mentioned the use of forensic analysis in crime investigations.
They have described all the science well, for example meiosis, which shows a thorough understanding of the topic. However, they have included many diagrams within the coursework, which are clearly copied from books or the internet, but not referenced them. This is an example of plagiarism. Although in this case, it appears to be accidental, this can lead to disqualification. Diagrams can be copied from books and the internet, as long as their original source is quoted and clearly stated, but it is a good idea to do this only if you also include some of your own writing to summarise the image and thus show you understand it.
Despite this, they have shown a thorough understanding of the topic and analysed data and ideas well.

Quality of writing

The report is well written, with a few minor grammatical and spelling errors. They have kept a good, formal tone throughout, as is suitable for the target audience. The report is split into sections on key topics, indicated by sub-headings. This makes it very easy to read and thus mark. They have used many relevant scientific terms, only once conflating 'molecules' with 'bases' - it is a good idea to learn definitions of difficult terms in order to avoid getting things confused.
Their quality of written communication is generally very good, and the report therefore is easy to read and shows off their scientific understanding and vocabulary.

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Reviewed by dragonkeeper13 28/06/2012

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