T6 variation and evolution Flashcards
what is variation
differences in the characteristics of individuals in a population
what are the causes of variation within a species
genetics
environment
what is genetic variation
variations in the genotypes of organisms of the same species due to the presence of different alleles
creates differences in phenotypes
what creates genetic variation in a species
spontaneous mutations
sexual reproduction
3 types of gene mutation
insertion
deletion
substitution
how may a gene mutation affect an organisms phenotype
neutral mutation doesn’t change the sequence of amino acids, protein structure and function same, no effect
mutation may cause minor change in phenotype
may completely change the sequence of amino acids, resulting in a non-functional protein, severe changes to phenotype
consequence of a new phenotype caused by a mutation being suited to an environmental change
rapid change in the species
what is evolution
gradual change in the inherited trains within a population over time
occurs due to natural selection which may result in the formation of a new species
outline the theory of natural selection
all species of living things have evolved from simple life forms that first developed more than 3 billion years ago
- genetic variation exists due to spontaneous mutations
- selection pressures exist
- random mutation gives an organism a selective advantage
- organism is better adapted to the environment and survives
- organism reproduces, passing on its beneficial alleles
- frequency of advantageous alleles increases
how do two populations become different species
when their phenotypes become different to the extent that they no longer interbreed to produce fertile offspring
outline main steps in selective breeding
- identify desired characteristic
- select parent organisms that show the desired traits and breed them together
- select offspring with desired traits and breed them together
- process repeated until all offspring have the desired traits
examples of characteristics selected for in selective breeding
disease resistance in crops
higher milk or meat production in animals
large flowers
advantages of selective breeding
creates organisms with desirable features
where is selective breeding useful
medical research
sport eg horse racing
agriculture
outline the disadvantages of selective breeding
reduction in the gene pool (becomes harmful is sudden environmental change occurs)
inbreeding results in genetic disorders
development of physical problems
potential to unknowingly select harmful recessive alleles
what is genetic engineering
modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be cut out and transferred to cells other organisms
enables the formation of an organism with beneficial characteristics
what is a use for genetically modified bacteria cells
produce human insulin to treat diabetes mellitus
describe the effects of genetic engineering
increased crop yields for growing population
useful in medicine possibly to overcome some inherited disorders
GM crops produce scarce resources (golden rice produces beta-carotene (source of VA in body))
risks of genetic engineering
long-term effects of consumption of GM crops unknown
negative environmental impacts
late-onset health problems in GM animals
GM seeds are expensive, LEDC may be unable to afford or may become dependent on businesses that sell them
what is bacillus thuringiensis (Bt)
insect larvae are harmful to crops
bacterium which secretes a toxin that kills insect larvae
how is genetic engineering used to protect crops against insects
gene for toxin production in Bt can be isolated and inserted into the DNA of crops
Bt crops now secrete toxin which kills any insect larvae that feed on it
benefits of Bt crops
increased crop yields
lessens need for artificial insecticides
Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it
risks of Bt crops
long term effects of consumption unknown
insect larvae may become resistant to toxin
killing reduces biodiversity
describe the process of genetic engineering
- DNA is cut at specific base sequences by restriction enzymes to create sticky ends
- vector DNA cut using the same restriction enzymes to create complementary sticky ends
- ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA
- recombinant DNA mixed with and taken up by target cells
what is a vector
structure that delivers the desired gene into the recipient cell
how can plants be cloned
taking plant cuttings
tissue culture
what is tissue culture
using small groups of cells from part of a plant to grow identical new plants
describe how plants are grown using tissue culture
- select a plant showing desired characteristics
- cut multiple small sample pieces from meristem tissue
- grow in a petri dish containing growth medium
- transfer to compost for further growth
what must be ensured when preparing tissue culutres
aseptic conditions to prevent contamination by microorganisms
what does the growth medium contain
nutrients and growth hormones
advantages of growing plants by tissue culture
fast and simple process
requires little space
enables growth of many plant clones with same desired characteristics
useful in preservation of endangered plant species
disadvantages of growing plants by tissue culture
reduction in gene pool
plant clones often have a low survival rate
could unknowingly increase the presence of harmful recessive alleles
brief overview of plant cuttings method of plant cloning
older but simpler method than tissue culture
gardeners use this method to produce many identical new plants from a parent plant
detail the process of plant cuttings method of plant cloning
- branch is cut off from the parent plant
- lower leaves of the branch are removed and the stem is planted
- plant hormones are used to encourage new root development
- plastic bag covers the new plant to keep it warm and moist
- new roots and a new plant is formed after a few weeks
what does embryo transplanting involve
pre-specialised cells from a developing animal embryo are spilt apart
resulting separate but identical embryos are transplanted into host mothers
describe how adult cell cloning is performed
- nucleus removed from unfertilised egg cell
- nucleus from adult body cell is inserted
into the egg cell - electric shock stimulates the nucleated egg to divide and it forms an embryo
- embryo cells contain the same genetic information as the adult body cell
- when the embryo is a ball of cells, inserted into the uterus to continue developing
