b6 Flashcards
what is variation?
- differences in characteristics of individuals within a population
state the three causes of variation
- genetical
- environmental
- both
what are mutations?
- a change in the DNA code, so the proteins are different
how do mutations lead to genetic variation?
- mutations take place all the time.
- most mutations have no effect on the phenotype.
- some mutations can determine the phenotype.
what were the first life forms on Earth?
- the first life forms on Earth were very simple (single cells)
what does evolution by natural selection mean?
- fittest individuals selected to survive.
state an example of natural selection of rabbits
- rabbits with inherited alleles for thicker fur are more likely to survive colder temperatures than rabbits with thin fur.
- so, rabbits with thicker fur can survive the cold.
- they will go on to reproduce.
- the offspring could inherit the alleles for thicker fur.
- they are more likely to survive the cold and reproduce.
what is evolution?
- development of a new species.
what happens when two populations become different in phenotype?
- they can no longer interbreed to produce fertile offspring.
what is selective breeding?
- breeding the best animals and plants together to create better offspring.
give four examples of selective breeding and explain why
- cows - better meat or milk
- crops - that are resistant to diseases
- pets - so we keep them as pets
- flowers - more colourful or larger
how is selective breeding carried out?
- take a look at the existing stock
- select the ones with good characteristics
- then breed them together to create the next generation
- repeat this process over and over again
what are the problems with selective breeding?
- it reduces the gene pool
- it could lead to inbreeding - more prone to diseases.
how are GM crops produced?
- by transferring genes into the crops.
why are plants genetically modified?
- to produce greater yield (produce) than normal crops
- resistant to disease or insect attack
- bigger and better crops
why are people against GM crops?
- we do not know how they may affect our health
- they could change the ecosystem
what is gene therapy?
- giving an individual the healthy version of a gene.
what are the steps for genetic engineering?
- isolate the gene you want using enzymes.
- insert the gene into a vector
- insert the vector into whichever organism you want to have the gene
- the organism will now take up the vector and the useful gene to produce the protein the gene codes for
what are fossils?
- things that have been left behind by long-dead organisms
state three ways in which fossils are formed?
- gradual replacement by minerals = shells/teeth/bones
- casts and impressions = footprints
- preservation = remain completely in tact
what are the problems with fossils?
- changes to rocks have destroyed them.
- there are very few fossils of the early life forms, so scientists cannot be certain how life began.
what is meant by extinction?
- no individual of that species remain.
state four reasons why species become extinct
- environmental changes
- new predator
- new disease
- catastrophic event (asteroids)
describe bacteria
- bacteria can evolve rapidly, as they reproduce at a fast rate.
- antibiotics kill bacteria
- they are used in farming and medicine.
how do bacteria become antibiotic resistant?
- a population of bacteria infect somebody
- the person takes antibiotics to kill the bacteria
- some of the bacteria get a random mutation
- bacteria grow and multiply
- more mutations arise leading to greater resistance
- there is now a strain of bacteria that antibiotics cannot kill
how do you reduce the development of antibiotic resistant bacteria?
- doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections.
- patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.
- the agricultural use of antibiotics should be restricted.
what are the problems with developing new antibiotics?
- takes a long time
- expensive
- hard to keep up with the emergence of new resistant strains
what classification system did Carl Linnaeus come up with?
- The Linnaeus System
how do you name organisms using a binominal system?
- by grouping species with similar characteristics and bone structure.
describe the three domain system
- bacteria = true bacteria which live in the human digestive system.
- eukaryote = include animals, plants, fungi and protists.
- archaea = primitive (ancient) bacteria found in extreme conditions like hot springs.
what is an evolutionary tree?
- it shows us the evolutionary relationships between different species or groups.
what data is used for an evolutionary tree?
- the structure and DNA of different species.
what are the problems with an evolutionary tree?
- the fossil records are not complete with many species.
describe sexual reproduction
- the fusion of male and female gametes
- genetically different
- lots of variation
- 2 parents
state the process of meiosis
- All the chromones are copied (now 46 pairs of chromosomes).
- The cell divides in 2 (23 pairs of chromosomes).
- They then divide again – 4 GAMETES PRODUCED (23
chromosomes).
describe asexual reproduction
- only 1 parent
- no genetic variation
- identical clones
what is fertilisation?
- the fusion of an egg and sperm cell
- what happens after fertilisation?
- the new cell divides by mitosis, producing a clump of identical cells called an embryo.
- the cells differentiate, forming different cell types.
describe the structure of DNA
- it is a polymer - similar units stuck together.
- it has two strands, which form a double helix.
what is a gene?
- a small section of DNA that codes for a protein
what is a genome?
- an entire set of genetic material in an organism
state the benefits for studying the human genome
- it can be used to identify diseases
- inherited diseases see the migration of our ancestors
what is cystic fibrosis?
- a disorder of cell membranes
what is polydactly?
- when an individual is born with an extra finger or toe
what kind of condition is cystic fibrosis?
- recessive
what kind of condition is polydactyly?
- dominant
what is the genotype of someone with cystic fibrosis?
ff
what is the genotype of a carrier of cystic fibrosis?
Ff
what is the genotype of someone with polydactyly?
Pp
what happens in embryo screening?
- a procedure carried out to test whether embryos have any problems with their chromosomes.
what are the problems with embryo screening?
- unethical = as embryos are destroyed
- expensive
- it could suggest people with genetic disorders are undesirable.
what is gene therapy?
- giving an individual the healthy version of the gene.
what combination of chromosomes determines a male?
XY
what combination of chromosomes determines a female?
XX
define gamete
the half of genetic material - a sex cell
define chromosome
separates sections in our DNA
define gene
a small section of DNA that codes for a protein
define allele
different versions of a gene
define dominant
the allele that is always expressed (F)
define recessive
the allele that is not expressed (f)
define homozygous
two copies of the same allele
define heterozygous
have two different alleles
define genotype
tells us the allele is present
define phenotype
tells us the characteristics caused by a person’s alleles
