Topic 4 - Natural Selection & Genetic Modification Flashcards
Process of Tissue Culture
1) Select plant you want to clone based on its characteristics
2) Remove small pieces of tissue from the parent plant . Best results if you take tissue from fast growing root / shoot tips
3) Grow tissue in a growth medium containing nutrients + growth hormones under aseptic (sterile) conditions to prevent growth of microbes which harm plants.
4) Tissue produces shoots and roots and then this is moved to a potting compost to carry on growing
Process of tissue culture of animal cells
1) Select a tissue sample e.g. tissue from pancreas is extracted from animal
2) Cells in sample are separated using enzymes
3) Separated cells are grown in culture vessels + bathed in a growth medium, containing nutrients
Tissue Culture Advantages
IN MEDICAL RESEARCH
• investigate effect of glucose on cells in pancreas —> by growing pancreatic cells
• You can look at the effects of a particular substance or environmental change on cells of a single tissue
Define Genetic Engineering
modifying an organism’s genome (DNA) to introduce desirable characteristics
Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics
PROCESS WITH USING ENZYMES
• use restriction enzymes to remove the gene & cut the plasmid
• use ligase enzymes to join DNA molecules together at their sticky ends —> (short section of unpaired bases)
• recombinant DNA is formed —> 2 different bits of DNA stuck together
Describe the main stages of genetic engineering including the use of :
a) restriction enzymes
b) ligase
c) sticky ends
d) vectors
1) A restriction enzyme cuts up the desired gene. Vector (carrier) DNA cuts open using same restriction enzyme.
2) Mix the DNA’s together by using ligase enzymes at the gene’s sticky ends.
3) Recombinant DNA (vector containing new DNA) is inserted into bacteria cells
—> bacteria cells use inserted gene to make the protein you desire
Advantages & Disadvantages of Genetic Engineering
ADVANTAGES
in agriculture
• crops become resistant to herbicide (weed killers)
—> increases crop yield, kills weeds without the crop being damaged
• crops become insect resistant —> less insecticides are needed
in medicine :
• GM bacteria produced human insulin & this is essential for people with Type 1 diabetes —> cheap & easy to obtain
DISADVANTAGES
• hard to predict what effect GM its genome will have on the organism
—> many embryos don’t survive
—> some GM animals suffer with health problems later in life
in GM crops :
• resistance in GM plants could pass on to wild plants
• GM crops could adversely affect food chains / harmful to human health
Define Selective Breeding
When humans artificially select plants / animals that are going to breed & genes for certain characteristics remain in the population
Why? To develop features that are more useful / attractive
e.g . Animals that produce more meat or milk
• crops with disease resistance
• dogs with a good, gentle temperament
• plants that produce bigger fruit
Selective Breeding
• Select desired trait from organism
• breed them together
• select best offspring & breed them together
• repeat process over several generations —> desirable trait gets stronger
Advantages & Disadvantages of Selective Breeding
ADVANTAGES – important in agriculture (farming)
•Genetic Variation —> some cattle have better characteristics for producing meat than others
• improves meat yield —> select cows & bulls with these characteristics + breed them together
—> select best offspring for several generations
—> outcome : cows with a higher meat yield
• used in medical research to investigate reasons behind alcoholism
• rats are bred with strong / weak preference for alcohol. Allowed researches to compare differences in behaviour + how the brain works
DISADVANTAGES
• reduces gene pool - number of different alleles in a popularion —> less variation within population “inbreeding”
• inbreeding causes health problems
—> organisms can inherit harmful genetic defects due to limited gene pool .
• less variation in a population —> this means a disease can wile out a population since there’s a less chance of resistant alleles being present
Explain Darwin’s theory of evolution by natural selection
• he noticed there was genetic variation within same species due to mutations in DNA
—> organisms with characteristics most adapted to the environment are most likely to survive + breed successfully (natural selection)
• inheritance - characteristics could be passed on to offspring
Natural Selection
a process where organisms with characteristics are better adapted to their environment
—> causes better chance of survival
—> more likely to breed successfully
Genetic variation
Differences in alelles.
—> new alleles arise through mutations
—> causes change in DNA
—> protein is different
Describe how the anatomy of the pentadactyl limb provides scientists with evidence for evolution
The similarity in bone structure provides evidence that species with a pentadactyl limb have all evolved from a common ancestor
Describe the evidence for human evolution bases on stone tools
Development of Stone Tools
homo habilis - used basic pebble tools by hitting rocks together —> creates sharp flakes —> uses to scrape meat from bones / crack bones open
Homo erectus sculpted rocks into shapes —> complex tools (hand-axes) use: hunt, dig, chop and scrape meat from bones
