b13- variation and evolution Flashcards
what is variation?
all the differences in the characteristics of individuals in a population
variation may be due to differences in:
-the genes they have inherited (e.g blood group)
-the conditions in which they have developed(environmental)
-a combination of genes and the environment (e.g height)
is there usually a massive amount of genetic variation within a population of a species?
yes
all of this genetic variation is due to?
mutations
what are mutations?
random changes to DNA
effect of mutations
-most have no effect on the phenotype
-some influence the phenotype
-very few determine the phenotype
mutations occur
continiously- very rarely a mutation will led to a new phenotype
if the genotype is suited to an environmental change, what can it lead to?
a relatively rapid change in the species
what does selective breeding involve?
-choosing parents with desired characteristics from a mixed population
-they are bred together
-from the offspring, those with the desired characteristics are bred together
-this continues over many generations until all offsprings show desired characteristics
what is evolution?
a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
what does the theory of evolution by natural selection state?
that all species of living things have evolved from simple life forms that first developed more than three billion years ago
what does evolution occur through?
natural selection of variants that give rise to phenotypes best suited for their environments
give an example of evolution
-environment gets colder, rabbits with alleles for thicker fur are more likely to survive that rabbits with thinner fur
-those with thicker fur–>more likely to survive + reproduce
if two populations of one species become so different in phenotype what can happen?
they can no longer interbreed to produce fertile offspring- they have formed two new species
what is modern medical research exploring?
the possibility of genetic modification to overcome some inherited disorders.
problems with genetic engineering:
-some people have ethical objections to genetic engineering
-benefits and risks associated with genetic engineering in agriculture and medicine
what is selective breeding?
a process by which humans breed plants and animals for particular genetic characteristics
examples of how humans have been doing this for thousands of years
-first bred food crops from wild plants and domesticated animals
what are some characteristics that can be chosen for usefulness or appearance?
-diseases resistance in food crops
-animals which produce more meat or milk
-domestic dogs with a gentle nature
-large or unusual flowers
selective breeding can lead to interbreeding. what does this mean?
-some breeds are particularly prone to disease or inherited defects
What is genetic engineering?
a process which involves modifying the genome of an organism by introducing a gene from another organism to give desired characteristic
how have plant crops been genetically engineered?
to be resistant to disease or produce bigger, better fruits
how have bacterial cells been genetically engineered?
to produce useful substances such as human insulin to treat diabetes
what can happen to the genes from the chromosomes of humans and other organisms in genetic engineering?
they can be ‘cut out’ and transferred to cells of other organisms (e.g bacteria)
what are crops that have had their genes modified called?
genetically modified (GM)crops
GM crops include ones that are ?
resistant to insect attack or herbicides
what do GM crops usually show?
increased yields
what do concerns about GM crops include:
-the effect on populations of flowers and insects
-some people feel the effects of eating GM crops on human health-not fully explored
what is modern medical research exploring?
the possibility of genetic modification to overcome some inherited disorders
what is the first step in genetic engineering?
-identify the gene we want to transfer (human gene, another animal or gene from plant)
the second step in genetic engineering
enzymes are used to isolate the required gene: the gene is inserted into a vector,usually a bacterial plasmid or a virus
the third step in genetic engineering
the vector is used to insert the gene into the required cells
the fourth step in genetic engineering
genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development –> so they develop with desired characteristics
