Inheritance, Variation and Evolution Flashcards
what is meiosis
the formation of four non identical cells from one cell
what is mitosis
the formation of two identical cells from one cell
what is sexual reproduction
the joining of male and female gametes, each containing genetic information from the mother or father
what are the gametes in animals
sperm and egg cells
what are the gametes in flowering plants
pollen and egg cells
how are gametes formed
meiosis
how do we know gametes are formed by meiosis
they are non identical
how many chromosomes does a normal cell have
46 chromosomes
how many chromosomes do gametes ahve
23 chromosomes
when do the gametes chromosomes fuse
fertilisation
what happens when gametes fuse
genetic information from each parent is mixed producing variation in the offspring
what is asexual reproduction
one parent with no gametes joining
how does asexual reproduction happen
mitosis
what does asexual reproduction lead to
clones that are genetically identical to eachother and the parent
examples of organisms produced by asexual reproduction
bacteria
some plants
some animals
process of meiosis
cell makes copies of its chromosomes so it has double the genetic information
the cell divides into two cells each with half the amount of chromosomes
the cell divides again predicting four cells each with a quarter of the amount of chromosomes
these cells are called gametes and are genetically different from eachother
why are gametes genetically different from eachother
the chromosomes are shuffled during the process resulting in random chromosomes ending up in each of the four cells
what happens during fertilisation of gametes
fuse and produce a cell with 46 chromosomes
this cell divides by mitosis to produce many copies
more and more cells are produced and an embryo forms
the cells are differentiated and take on different roles after this stage
advantages of sexual reproduction
produces variation in offspring
allows us to use selective breeding
advantages of asexual reproduction
only one parent is needed
uses less energy and is faster as organisms do not need to find a mate
in favorable conditions lots of identical offspring can be produced
why is producing variation in offspring an advantage
if the environment changes an organism of the species will have a characteristic that gives them a survival advantage
decreases the chance of the whole species becoming extinct
why is selective breeding an advantage of sexual reproduction
organisms with desirable characteristics can be bred
speeds up natural selection
which organisms use asexual and sexual reproduction to reproduce
malarial parasites
some fungi
some plants
how do malarial parasites use s and a reproduction
reproduce sexually in the mosquito
reproduce asexuallly in the human host in the liver and blood cells
how do some fungi reproduce both ways
spores produced asexually are genetically identical
spores are produced sexually when the conditions change in order to increase variation and avoid extinction
how do some plants reproduce both ways
many reproduce sexually using pollen which reaches egg cells int he female parts of another flower (pollination)]
strawberry plants reproduce asexually as they produce runners which new identical plants grow off
daffodils reproduce asexually and grow from bulbs that grow off the main one
why is asexual reproduction advantageous in plants
they can reproduce even if the flowers have been destroyed by frost or other animals
what is the genetic material in the nucleus composed of
a chemical called DNA
what is DNA
a polymer made of two strands which wrap around eachother in a double helix structure
where is the DNA in the nucleus contained in
chromosomes
what are between the 2 strands of DNA
four nitrogenous bases lined up in single rows that come together to form a series of complementary pairs
what is a gene
a small section of DNA on a chromosome
what does a gene compose of
a triplet of bases that codes for a specific protein
what does each gene code for
a particular sequence of amino acids that can chain together to make a protein
what is a genome
all the genes coding for all of the proteins within an organism
what has the human genome being studied helped with
improved understanding of genes linked to disease
treatment of inherited disorders
tracing human migration patterns from the past
what does DNA stand for
deoxyribonucleic acid
what are chromosomes
structures made up of long molecules of DNA found in the nucleus of a celll
what is DNA made up of
small parts called nucleotides
what is each nucleotide made up of
one sugar molecule
one phosphate molecule
one of the four types of organic bases
what are the four types of organic bases
A
C
G
T
what is each dna molecule made up fo
two dna strands twisted together
how are the bases connected in dna strands
each base is connected to another base in the other strand
what bases connect
A and T
G and C
what is bases connecting called
complementary base pairing
what do the order of different bases form
a code
what does each group of three bases code for
an amino acid
what determines the type of protein
the types and order of amino acids in the chain
how many types of amino acids are there
20
what do the non coding parts of dna do
do not code for proteins
some switch genes on or off
what is protein synthesis
the process of producing a protein from DNA
what does it mean if a gene is coded to make a protein
it has been expressed
process of protein synthesis
dna cannot move out of the nucleus as it is too big
the two strands pull apart from eachother and mRNA molecules match to their complementary base on the strand
the mRNA nucleotides are joined together creating an mRNA strand which is a template of the original dna
the mrna then moves out of the nucleus to the cytoplasm and onto ribosomes
at the ribosomes the bases on the mrna are read in threes to code for an amino acid
the corresponding amino acids are brought to the ribosomes by carrier molecules
these amino acids connect to form a protein
when the chain is complete the protein folds to form a unique 3D structure
what does the proteins specific shape help
helps it to carry out its role
what can proteins be
enzymes
hormones
structural protein
what are structural; protein
strong proteins in order to form structures such as collagen
what do mutations do
change the sequences of bases in DNA
which three ways can mutations occur
a base is inserted into the code
a base is deleted from the code
a base is substituted
how does a base being inserted into the code cause a mutation
as they are read in threes, it changes the way it is read
it may change all the amino acids coded for after this insertion
how does a base being deleted from the code cause a mutation
they change the way it is read
it may change all the amino acids coded for after this deletion
how does a base being substituted cause a mutation
changes one amino acid in the sequence
or it may not change the amino acid because the new sequence can sometimes still code for the same amino acid
what does a change in the sequence of amino acids affect
the way it folds and therefore the structure
how do most mutations affect the protein
do not alter it or only do so slightly
what can some mutations do to the protein
have a serious effect and change the shape
what is the effect of a mutation changign the shape of a protein
the substrate will not fit into the active side so it cannot act as a protein
a structural protein may lose its shape
where can mutations also occur
in the non coding parts of dna that control whether the genes are expressed
why does variation between two organisms arise
the coding DNA that determines the proteins and their activity
the non coding dna that determines which genes are expressed
what is an allele
the different forms of a gene
what is a dominant allele
only one out of the two alleles is needed for it to be expressed and for the corresponding phenotype to be observed
what is a recessive allele
two copies are needed for it to be expressed and for the corresponding phenotype to be observed
what does homozygous mean
when both inherited allele are the same
what does heterozygous mean
one of the inherited alleles is dominant and the other is recessive
what is a genotype
the combination of alleles an individual has e.g Bb
what is a phenotype
the physical characteristics that are observed in the individual
what do family trees show
the inheritance of different phenotypes over generations in the same family
what are genetic disorders caused by
inheriting certain alleles
what is polydactyly
having extra fingers or toes
what is polydactyly caused by
a dominant allele
what is cystic fibrosis
a disorder of the cell membranes resulting in thick mucus in the airways and pancreas
what is cystic fibrosis caused by
a recessive allele
both parents need to either be carriers or one must have CF themselves and the other is a carrier
what does embryonic screening do
allow scientists to observe whether the child will have a genetic condition or not
what happens if the embryo is developed in the lab
cells can be taken from it and analysed
what are advantages of embryonic screening
reduces number of people suffering
treating disorders is very expensive
many regulations are in place to stop it getting out of hand
disadvantages of embryonic screening
could encourage people to pick characteristics for babies
expensive to carry out screening
promote prejudice as it suggests those with genetic disorders are unwanted
decisions about terminating a pregnancy have to be made
procedure can lead to a miscarriage
what do 22 of the pairs of chromosomes do
control characteristics and the chromosomes in each pair look very similar
what does the 23rd pair of chromosomes do
carries sex determining genes and the two chromosomes can look different to eachother
what are the two possible chromosomes in the 23rd pair
X and Y chromosomes
what happens when cells undergo meiosis to form a gamete
one sex chromosome goes into each gamete
how many x chromosomes do females have
two
which chromosomes do females pass on in their eggs
only x chromosomes
which chromosomes do males have
one x and one y chromosome
which chromosomes do males pass on
x or y chromosomes in sperm
what is the percentage of having a male pr female
50%
what does the phenotype of an organism depend on
genotype
environment
how does genotype change phenotype
genes are passed on from the parent in sex cells
the combining of genes from the mother and father creates genetic variation
only identical twins have the same genotype
there is lots of genetic variation in a population
how does environment affect phenotype
the conditions the organism grows and develops in also affects its appearance
examples of environmental changes to phenotype
scars in animals
smaller or yellow leaves in plants
which phenotypes are a result of genetics and the environment
weight
how is weight affected by genetics and environment
depends on the food you eat
but also how quickly your body breaks it down and how much fat it stores depends on genes
what is genetic variation introduced by
introduced by mutations in the sequence of DNA
how does genetic variation affect phenotype
most have no effect on phenotype
some influence phenotype but unlikely to bring a new phenotype
if brings a new phenotype and it is advantages natural selection will make it the most common phenotype quickly
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 is the theory of evolution
all species have evolved from simple life forms that first developed more than three billion years ago
why does evolution occur
natural selection
process of natural selection
mutations occur which provide variation between organisms
if a mutation provides a survival advantage the organism is more likely to survive to breeding age
the mutation will then be passed onto offspring
over many generations the frequency of the mutation will increase within the population
what can natural selection cause
speciation
what is speciation
one population of a species becomes so different that they can no longer interbreed to produce fertile offspring so they have become a new species
what is selective breeding
when humans choose which organisms to breed in order to produce offspring with certain desirable characteristics
examples of desirable characteristics from selective breeding
animals with more meat
plants with disease resistance
big flowers
when did selective breeding start
since animals were domesticated and plants were grown for food
process of selective breeding
parents with desired characteristics are chosen
they are bred together
from the offspring those with desired characteristics are bred together
the process is repeated many times until all the offspring have the desired characteristic
what can selective breeding lead to
inbreeding
what does breeding those with similar desirable characteristics man
it is likely you are breeding closely related individuals
what does inbreeding lead to
reduction of the gene pool as no of different alleles reduces
so if the environment changes or there is a new disease the species could become extinct as they ahve the same genetic makeup - less ahve survival advantages
greater chance of genetic defects in the offspring as recessive characteristics more present
what is genetic engineering
modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
how have plant cells been engineered
for disease resistance or to have larger fruits
how have bacterial cells been engineered
to produce substances useful to humans such as human insulin to treat diabetes
process of genetic engineering
1.genes from chromosomes are cut out using restriction enzymes leaving sticky ends (short sections of exposed, unpaired bases)
2. a virus or bacterial plasmid is cut using the same restriction enzyme to create sticky ends, this also contains an antibiotic marker gene
3. the loop and gene sticky ends are then joined together by DNA ligase enzymes
4. the combined loop is placed in a vector such as a bacterial cell ad allowed to multiple as it contains the modified gene
as the bacteria grows we can see which ones are resistant to antibiotics
the colonies are the bacteria that are also producing the modified gene as they were inserted together
where is the vector put in genetic engineering in plants
vector is put into meristematic cells which can then produce identical copies of the modified plant
what are genetically modified crops produced for
to be resistant to insects and herbicides
results in increased yields as less crops will die
what is genetic modification in medicine used for
cure inherited disorders using gene therapy to transfer normal genes into patients so the correct proteins are produced
benefits of genetic engineering
useful in medicine to mass produce certain hormones in microorganisms
used to crease yields in agriculture
crops with extra vitamins can be produced in areas where they are difficult to obtain
greater yields can solve world hunger which is increasing
how does genetic engineering improve yields in agriculture
improves growth rates
introduces modifications that allow the crops to grow in different conditions
introduces modifications that allow plants to make their own pesticide or herbicide
risks of genetic engineering
GM crops might have an effect on wild flowers therefore insects
we don’t understand the effects of GM crops on human health
GE in agriculture could lead to GE in humans - designer babies
selection pressure leading to increased resistance in other species
how can genetically modified crops have an effect on wildflowers and insects
they are infertile and these genes could spread to wild plants leading to infertility in other species
growing with herbicides and pesticides can kill insects and other plants, reducing biodiversity
what is cloning
creating genetically identical copies of an organism
methods of plant cloning
tissue culture
cuttings
methods of animal cloning
embryo transplants
adult cell cloning
what is tissue culture important for
preserving rare plant species or commercially in plant nurseries
process of tissue culture
plant cells are taken
they are placed in a growth medium with nutrients and hormones
they grow into new plants and are clones as they are genetically identical to the parent
process of cuttings
cuttings such as a section of the stem are taken from a plant with a desirable feature
they are planted and produce clones as they are genetically identical to the parent
embryo transplants process
sperm cells and egg cells from parents with desirable features are obtained
in the lab they are fertilised to form an embryo
the embryo divides many times and is then inserted into a host mother
the offspring which is eventually born is genetically identical as they have genetic information from the same mother and father
adult cell cloning process
nucleus removed from an unfertilised egg cell
the nucleus is removed from an adult body cell and placed in the denucleated egg cell
electric shock stimulated the egg cell to divide to form an embryo
the embryo is implanted into the womb of a female
the offspring is born as a clone of the adult body cell
benefits of cloning
produces lots of offspring with a specific desirable feature
study of clones could help research into embryo development
can help extremely endangered species or even bring back species that have become extinct
risks of cloning
the gene pool is reduced so it is less likely that the population will survive if a disease arises with low diversity in the population
clones have a low survival rate and have some genetic problems
may lead to human cloning
who was charles darwin
a scientist and naturalist
what did charles darwin do
put forward the theory of evolution
what was charles darwin’s theory of evolution supported through
the experimentation and his knowledge of geology and fossils that he discovered on a round the world expedition
what did charles darwin publish
‘on the origin of species’ in 1859
what is the theory of evolution
variation exists within species as a result of mutations in dna
survival of the fittest
beneficial characteristics are passed onto the next generation
over many generations the frequency of alleles for the advantageous characteristic increase in the population
what is survival of the fittest
organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully
why was there controversy around the idea of evolution
contradicted idea that god was created of all species on earth
not enough evidence at the time as few studies had been done on how organisms change over time
mechanism of inheritance and variation not known at the time
what did jean baptiste lamarck think about evolution
changes that occurred during the lifetime of an organism were passed onto offspring
if an indiviso continually repeated an action the characteristic that allowed it to do this would develop further eg a giraffe stretching neck
tu his characteristic would be passed onto its offspring
when was lamarcks theory proven wrong
when it was understood that changes caused by the environment were not passed on in the sex cells
why was darwin’s theory suppprted
suppported by genetics as it provided a mechanism for beneficial characteristics caused by mutations to be passed on
fossil evidence showed how developments in organisms arose slowly
what is speciation
the process of a new species developing through the selection of different alleles which increases the genetic variation until the new population cannot breed with those in the old population to produce fertile offspring
who developed the theory of speciation
alfred russel wallace
how did alfred russel wallace develop theory of speciation
on his travels he had the idea that individuals who did not have characteristics to help them survive a change in the environment would die out
he published joint studies with darwin
he collected evidence eg warning colouration in animals
what is the process of speciation
variation exists within a population as a result of genetic mutations
alleles which provide a survival advantage are selected for through natural selection
populations of a species can become isolated for example through physical barriers such as a rock fall preventing them from breeding together
different alleles may be advantageous to the new environments leading them being selected for
over time the selection of different alleles will increase the genetic variation between the two populations
when they are no longer able to breed together to produce fertile offspring, a new species has formed
what did gregor mendel do
trained in mathematics and natural history in vienna
observed characteristics passed on to the next generation in plants
carried out breeding experiments on pea plants
used different types of peas and observed offspring to see which characteristics they inherited
which conclusion did mendel come to
offspring have some characteristics that their parents have because they inherit hereditary units from each
one unit is received from each parent
units can be dominant or recessive and cannot be mixed together
why was mendel not recognised until after his death
genes and chromosomes were not yet discovered so people could not understand
when were chromosomes being part of cell division observed
late 19th century
when was it understood that chromosomes and units had similar behaviours
late 20th century
when was the structure of the dna determined
1953
where is evidence for evolution seen
fossils
antibiotic resistance
what are fossi;s
remains of organisms from millions of years ago which are found in rocks
what are fossils formed from
parts of organisms that have not decayed because oxygen or moisture were not present - microbes that cause decay cannot survive
parts of organisms such as teeth shell and bones are replaces by minerals as they decay forming a rock structure of the original plant
preserved traces such as footprints burrows and rootlet traces remain due to the ground hardening around them and forming a cast
what are fossils used to show
how the anatomy of organisms has changed over time
compare how closely related two organisms are
what can fossils not be used for
tell us how life started on earth
why can’t fossils be used to tell us how life started on earth
most early life forms are soft bodied and therefore decay completely so there are few fossils of them
any traces left have been destroyed by geological activity
what is extinction
when an entire species has died out
which factors contribute to extinction
changes in environment that species cannot adapt to
new predators evolved or migrated to area
new disease arises and no resistant alleles
have to compete with a species with advantageous mutations for the same food source
catastrophic event can wipe out a species
destruction of a habitat
when are bacteria labelled resistant
when they are not killed by antibiotics which previously were used as cures against them
how is antibiotic resistance caused
mutation during reproduction can result in a gene for antibiotic resistance
what does exposure to antibiotics create
a selection pressure as those with antibiotic resistant genes survive and those without die
so those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
the population of antibiotic resistant bacteria increases
why do bacterial diseases spread rapidly
people are not immune to new resistant bacteria and there is no treatment for it
what is MRSA
superbug that is resistant to many types of antibiotics
where is mrsa common
hospitals as it spread when doctors and nurses move to different patients
how to slow development of resistance in bacteria
antibiotics shouldn’t be given for viral or non serious infections
specific antibiotics should be given for specific bacteria
patients should complete their course of antibiotics so no bacteria survives and mutates
antibiotics should be used less in agriculture - antibiotic resistant bacteria transferred from livestock to humans in meat
how to slow transmission of antibiotic resistant bacteria
maintain high standards of hygiene in hospitals
medical staff and visitors should wash hands regularly
medical staff should wear disposable clothing or clothing that is regularly sterilised
why is it difficult to keep up with the development of resistant strains
the development of antibiotics is expensive and slow
what is classification
putting organisms into groups depending on their structure and characteristic so
who put forward the linnaean system
carl linnaeus in 1700s
what does the linnaean system do
divides living things into
kindgoms
phylum
class
order
family
genus
species
what does the binomial system do
gives each organism a name which is used worldwide
first part is their genus and second part is species
why was the three domain system developed
developments in science such as improvement of the microscope and increased knowledge of biochemistry found some species were more distantly related than first thought
who created the three domain system
carl woese
what are the three groups called domains above kingdoms
archaea
bacteria
eukaryote
what is archaea
primitive bacteria which live in extreme environments such as hot springs
what are bacteria
true bacteria
what are eukaryota
organisms who have a nucleus enclosed in membranes
includes the kingdoms protists , fungi, plants and animals
what are evolutionary trees used for
to show how closely related organisms are
how are evolutionary trees completed
they use classification data and fossils for extinct species
