CCEA GCSE biology - DNA and genetics

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cell division producing y gametes in 2 divisions with half the normal amount of chromosomes. It occurs in sex organs only, produces gametes, is reduction division (haploid), I cell produces y different cells in 2 divisions. Each chromosome in a pair can combine with either chromosome from another pair, there are millions of possible arrangements - independent assortment (major source of variation in humans) Genetics Genetics is the study of how characteristics pass from parent to child. Each gene carries the code for a particular characteristic. As chromosomes form in pairs but carries the same gene, they can have different forms (alleles) in the gene Homozygous-both alleles are the same Heterozygous- both alleles are different Genotype-paired symbols showing the allele arrangement of an individual Phenotype-outward appearance of an individual Dominant- in the heterozygous condition, the dominant allele in a gene overrides the recessive allele Recessive-dominated by the dominant allele- only shows as phenotype when in homozygous recessive condition Backcross-cross with homozygous recessive if dominant shows, genotype is Rr monk who carried out thousands of experiments on monohybrid characteristics In pea plants. He learned :certain traits are determined by factors within the organism (genes) the factors can be present in 2 different forms the 2 forms separate during gamete formation understanding of monohybrid ratios Gregor mendel Sex links Y chromosome has less genes so recessive on X will show in phenotype in men. I'm women, it can be masked by a dominant on the x Second X. (Sex linked diseases) Inherited-passed from parent to child Genetic condition- fault in genes or chromosomes (some are inherited) Genetic screening- testing a foetus or person for the presence of harmful alleles and abnormalities Amniocentesis- taking foetal cells from the amnion, growing them in a lab and testing no of chromosomes (1% miscarriage risk) Blood test at 10-14 weeks detects if risk is higher than normal and identifies those for amniocentesis, prevents having a child with bad quality of life time spent caring for baby takes away time from other siblings Should genetic info be made public: could help medical research could let insurance companies discriminate Genetic engineering unborn child has no say abortion is banned in countries or religions who decides who should be tested is there an acceptable risk cost of treatment over testing Genetic engineering- modification of the genome of an organism to introduce desirable characteristic, usually involves adding human genes to DNA of another organism to make whatever the human dna codes for. Bacteria cells are modified to produce human insulin. Restriction enzymes cut the human gene to leave overlapping sticky ends, same in the DNA (complimentary) making it easy to join by base pairing. Insulin extracted, purified and packaged (downstreaming) Advantages: Limited insulin was available before- only from dead animals at slaughterhouses (expensive) Human insulin is different than animal insulin so more effective Animal insulin could cause allergies Risk of virus spreading between animals and humans Disadvantages: Ethical reasons