Inheritance, Variation and Evolution Pt2 Flashcards
Work of Mendel, Variation, Selective breeding, Genetic engineering
What did Gregor Mendel do?
he experimented with pea plants to work out how traits are passed down from one generation to the next (despite chromosomes or genes being discovered).
What three conclusions did Gregor Mendel reach?
- characteristics in plants are determined by hereditary units
- hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
- hereditary units can be dominant or recessive ( if individual has both the dominant will be expressed )
What are the two types of variation?
genetic variation and environmental variation
How do mutations introduce variation?
- mutations are changes to the sequence of bases in DNA. they lead to changes in the protein that a gene codes for
- its very rare but mutations can result in a new phenotype being seen in a species
What is selective breeding?
when humans artificially select the plants or animals that are going to breed so the next generation have the desired characteristics wanted
What are the steps for selective breeding?
- From the existing stock, select the ones with the desired characteristics wanted
- Breed them together
- Select the best of the offspring and breed them together
- Continue this process over several generations and the desirable trait gets stronger and stronger
What are the disadvantages for selective breeding?
- it reduces the gene pool ( the number of different alleles in a population)
- inbreeding causes health problems (because there’s more chance of the organism inheriting harmful genetic defects when the gene pool is limited)
- if a new disease appears and one organism dies from it, the others are likely to also die from it because there’s not much variation and all the stock are closely related
What is genetic engineering?
Transferring a gene responsible for a desirable characteristic from one organisms genome into another organism, so it has the desired characteristic
What are the steps for genetic engineering?
- a useful gene is isolated from one organisms genome using enzymes and is inserted inside a vector
- the vector is usually a virus or a bacteria plasmid depending on the type of organism the gene is being transferring
- when the vector is introduced to the target organism, the useful gene is inserted into its cells
What are examples of genetic engineering?
- Bacteria have been genetically modified to produce human insulin that can be used to treat diabetes
- genetically modified crops have had their genes modified to improve the size and quality of their fruit or to make them resistant to disease, insects, herbicides
- sheep have been genetically modified to produces drugs in their milk that can be used to trat human diseases
What are the pros and cons of genetic engineering?
pros
- treating diseases
- more efficient food production
cons
- changing an organisms genes might accidentally create unplanned problems, which could get passed on top future generations
What are the pros and cons of genetically modified crops?
Pros
- chosen characteristics can increase the yield making more food
Cons
- it can affect the number of wild flowers and insects that live in and around the crops, reducing farmland diversity
- transplanted genes may get out into the natural environment
- not everyone is convinced that GM crops are safe and people are concerned that we don’t fully understand the effects on human health
What is the theory of evolution?
all of todays species have evolved from simple life forms that first started to develop over three billion years ago
What is survival of the fittest? And how does this cause evolution?
- organisms have to compete for resources
- the organisms with the most suitable characteristic for the environment are more successful competitors and more likely to survive ( survival of the fittest )
- the surviving organisms are more likely to reproduce and pass on the successful characteristics to offspring
- over time beneficial characteristics become more common in the population and the species evolves
What is extinction?
when no individuals of a species remain
Give some reasons can species become extinct
- a new predator
- a new disease kills them all
- they can’t compete with a new species for food
- a catastrophic event kills them all e.g. volcanic eruption or a collision with an asteroid
- environment changed too quickly
Why was Darwin’s theory controversial?
- it went against common religious beliefs at the time about how life on earth developed
- darwin couldn’t explain why new characteristics appeared or how they were passed on from individual organisms to their offspring ( he didn’t know anything about genes or mutations)
What was Lamarks theory?
he thought that if a characteristic was used a lot by an organism then it would become more developed during its lifetime and the organisms offspring would inherit the acquired characteristic
What evidence supported Darwin’s theory?
- the discovery of genetics because it provided an explanation of how organisms with beneficial characteristics pass them on
- fossils of different ages allows you to see how changes in organisms developed slowly over time
- bacteria are able to evolve to become resistant to antibiotics supports evolution by natural selection
What are the two ways plants can be cloned?
tissue culture & cuttings
What is tissue culture?
- a tissue sample is scraped from the parent plant
- a few of the plant cells are put in a growth medium with hormones
- they grow into new plants that are clones of the parent plant
These plants can be made very quickly, in little space and be grown all year. Its used by scientists to preserve rare plants that are hard to reproduce naturally and by plant nurseries.
What is cuttings?
- gardeners can take cuttings from parent plant each with a new bud on
- then plant them to produce genetically identical clones of the parent plant
These plants can be produced quickly and cheaply
What is the method for using embryo transplants? (use the example of a bull and cow)
- sperm cells are taken from a prize bull and egg cells are taken from a prize cow
- the sperm is then used to artificially fertilise an egg cell
- the embryo that develops is then split many times to form clones before any cell becomes specialised
- these cloned embryos can then be implanted into host mothers where they grow into genetically identical calves
What is the method for adult cell cloning?
- the nucleus is removed from an unfertilised egg cell
- the nucleus from an adult body cell is inserted into the egg cell
- an electric shock stimulates the egg cell to divide to form an embryo
- when the embryo is developed into a ball of cells its inserted into the womb of an adult female to continue developing
- It grows into a genetically identical clone of the adult body cell since it has the same genetic information
