Biology - B1.6 - Variation, Reproduction and New Technology

B1.6.1 - Inheritance

Cell nuclei contain chromosones, which carry genes
In the nucei of sex cells (gametes) there's only a single set of chromosones, so the nuclei of both a male and female sex cell would contain one set of genes
Genetic information is passed from parents to offspring, so the offspring have two sets of genes inherited from both parents
Different genes = control different characteristics
Chromosones are in pairs - one from each parent

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Asexual reproduction - gametes don't fuse, genetic information all from one parent, offspring identical to parent - little variation, identical copies that are formed called clones
Sexual reproduction - gametes fuse, mixing of genetic information - variation, sex cells (in animals) - sperm and egg, offspring similar to both parents but not identical - have two sets of genes
Random mixing of genes = variation - important for survival as some characteristics give offspring better chance of surviving in difficult conditions

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Different characteristics due to - genes, conditions and combination of both
Genes are the most important factor in controlling appereance
Plants affected by - light, nutrients and space - weaker plants with the same genes as a stronger plant but wouldn't grow as well
Human development affected during pregnancy - mother smoking or drinking can cause the baby to have a small birth weight
Too little/much food alter characteristics - eg. genes determine potentential to be an athlete but training and diet will also alter the body

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Clones - identical to parent
Cloning animals is harder than clonign plants
Used to produce new and useful, in farming and agriculture, individuals
Plant cloning -> cheap and effective - take cutting and grow it, or, more expensive - take small group of cells and grow them under special conditions (tissue culture) - used to reproduce large numbers of rare or top quality plants
Animal cloning -> embryo transplants - embryo with unspecialised cells spilt into smaller groups of cells, each group is transplanted and allowed to develop in a host animal
Can be genetically modified, before cloning, to produce useful substances

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Adult cell cloning - nucleus of adult cell (eg. skin cell) replaces nucleus of an egg cell - nucleus taken out of unfertilised egg -> nucleus from skin cell removed and placed inside 'empty egg' - > electric shock to start division -> ball of cells called embryo -> ball of cells put into womb of host mother
Embryo is genetically identical to to adult skin cell
Dolly the sheep - produced by adult cell cloning in 1997
Adv - cloned animals can be genetically engineered to have medical uses, can save animals from extinction
Disadv - ethical concerns, limits gene pool - cause problems for natural selection if environment changes, concerns about using it on humans in the future

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Genetic engineering - changing genetic make-up of organism
Genes can be transferred to animal, plant and microorganism cells at an early development stage
A gene is cut out of chromosone using enzyme -> gene placed in chromosone of another organism
Genes can be put in organism of same species for desired characteristics or a different species, eg. a bacterium - gene to produce human insulin can be put in bacteria, which can produce large amounts of insulin to treat diabetes
Genes can be transferred to crop plants - crops with changed genes = genetically modified (GM) crop plants - Gm crops can be insect/herbicide-resistant and usually have increased yields

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Adv and disadv in using clong and genetic engineering
Adv - clonging cattle = herds of cattle with useful characteristcs, adult cell cloning - copies of the best animals (eg. race horses), faulty gene = genetic disorder - correct gene transferred = cure, medical drugs been produced by genetic engineering (eg. insulin and antibodies), GM crops - insect/herbicide-resistant
Disadv - GM crops are infertile - farmer has to buy new seeds each year, concerns about introducing genes to wild flowers, non-pest insects affected by GM crops, effect o eating GM crops on human health, ethical? - long term effects, creating new organisms, ethically correct

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