GCSE Biology

make exactly the protiens needed andf in very pure form .

• to improve growth rates of planst and animals
• to improve the food value of crops and to reduce the fat levels in meat
• they are used to produce plants which make their own pesticides

• they may be genetically engineered so that they are resistant to herbicide meaning a farmer can srpary his weeds without killing his crops
• GM crops increase the yeild of a crop , making more food
• people living in LEDC'S often lack nutrients in their diet and GM crops could be conatin the nutrients that are missing

• the GM crop seeds may be expensive for farmers
• pollination may mean that if GM crops are nearby weeds the gene for herbicide resistance may be transfered to the weeds
• we dont know wheter eating GM crops over a long period of time will cause health problems

• humans may not have the right to gentically alter nature for their convinience and profits in some peoples opinions
• vegetarians may find it offensive to put animal genes into plants

your genetic material in the form of chromosomes

• 23
• chromosomes

genes . different genes control the devlopment of different characteristics

DNA

fusion of of male and fema tle gametes . Because there are two parenst , the offspring contain a mixture of their parents genes

one parent . there's no fusion of gametes , no mixing of chromosomes and no genetic variation between parent and offspring , the offspring are genetically identical to the parent - they are clones

• X shaped chromosmes have two identical halfs
• so each chromosome splits down the middle
• to form two identical sets of half chromosomes (i.e. two identical sets of DNA strands)
• a membrane forms around each set
• and the DNA replicates itself to form two identical cells with complete sets of X shaped chromosomes