Topic 6 - inheritance ,variation and evolution Flashcards
1
Q
what is DNA?
A
deoxyribonucleic acid
the chemical that all of the genetic material in a cell is made up from
It contains coded infornmation which determine what inherited characteristics you have
2
Q
where is DNA found in animals and plants
A
in the nucleus in realy long structures called chromosomes.
3
Q
what is the structure of DNA
A
DNA is a polymer
it is made up of two strands coiled together in the shape of a double helix .
4
Q
what is a gene and what do they do
A
a small section of DNA found on a chromosome
each gene codes for a particular sequence of amino acids which are put together to make a specific protein
only 20 amino acids are used but they make up thousands of different proteins
genes tell cells in what order to put the amino acids together.
5
Q
what s a genome
A
the entire set of genetic material in an organism
6
Q
why is understanding the human genome a really important tool for science and medicine
A
it allows scientists to identify genes in the genome that are linked to different types of diseases
knowing which genes are linked to inherited diseases could help us understand them better to develop effective treatments for them .
scientists can look at genomes to trace migration of certain populations of people around the world.
7
Q
where are all modern humans descended from
A
a common ancestor in africa
8
Q
What is DNA made up of
A
repeating units called nucleotides
each nucleotide consists of a sugar, a phosphate group and a base
the sugar and phosphate group in the nucleotides form a backbone to the DNA strands .
the sugar and phosphate groups alternate
one of four different bases joins to each sugar
each base links to a base on the opposite strand in the helix
9
Q
what are the four bases an what are their complementary base pairing
A
A - T
C - G
10
Q
what in a gene decides the order of amino acids in a protein
A
the order of the bases
11
Q
how many bases is an amino acid coded for
A
3 bases
12
Q
what do the parts of DNA that dont code for proteins do ?
A
some of the non coding parts switch genes on and off so they cotrol whether or not a gene is expressed
13
Q
where are proteins made
A
in ribosomes
14
Q
how do ribosomes make proteins
A
to make proteins , ribosomes use the code in the DNA
DNa is in the cells nucleus and cant move out of it because it is really big. - so the cell needs to get the code from the DNA to the ribosome .
THis is done using mRNA - ehich is made by copying the code from the DNA .
the mRNA acts as a messenger between the DNA and ribosome - it carries code between the 2 .
the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
15
Q
what happes when a chain of amino acids has been assembled
A
it folds into a unique shape which allows the protein to perform the task its meant to do
16
Q
describe what each of the following proteins do
enzymes
hormones
structural proteins
A
enzymes - act as biological catalysts to speed up chemical reactions in the body
hormones- used to carry messages around the body .
structural proteins - physically strong e.g. collagen - strengthens connective tissues
17
Q
are mutations random or not
A
a random change in an organisms dna
can sometimes be inherited
18
Q
what may increase the chance of a mutation
A
exposure to certain substances or some types of radiation
19
Q
what affect do mutations have on DNA
A
change the sequence of the DNA bases in a gene. which produces a genetic variant .
As the sequence of DNA bases codes for the sequence of amino acids that make up a protein , mutations can sometimes lead to changes in the protein that it codes for
20
Q
what effect do most mutation have on proteins
A
very little or no effect
some change it to a small extent that its function or appearance is unaffected
21
Q
what serious effect can some mutations have on proteins
A
sometimes the mutation will code for an altered rpotein with a change in its shape . this could affect its ability to perform its function
e.g.
if th eshape of an enzymes active site is changed - its substrate may no longer be able to bind to it .
structural proteins like collagen could lose their strength if their shape is changed , making them useless at providing structure and support
22
Q
what can happen if there is a mutation in the non coding DNA
A
it can alter how genes are expressed
23
Q
what are the three different types of mutation
A
insertions
this is where a new base is inserted into the DNA base sequence where it shouldnt be .
an insertion changes the way the groups of three bases are read which can change the amino acids they code for .
insertions can change more than one amino acid as they have a knock on effect on the bases further on in the sequence .
deletions
deletions are when a random base is deleted from the DNA base sequence
like insertions , they change the way that the base sequence is read and have knowck on effects further down the sequence .
substitutions
substitution mutations are when a random base in the DNA base sequence is changed to a different base.
24
Q
what is sexual reproduction
A
where genetic infornmation from two organisms is combined to produce offspring which are genetically different to either parent.
sexual reproduction involves the fusion of male and female gametes
25
how many chromosomes does each gamete in humans contain
23 chromosomes
26
why do human offspring inherit features from both parents
it recieves a mixture of chromosomes from its mum and its dad
this mixture of genetic infornmation produces variation
27
what is asexual reproduction
there is only one parent so the offspring are genetically identical to the parent
happens by mitosis
the offspring are clones of the parents
28
describe the process of meiosis
genetic info is duplicated , the chromosomes then arrange theirselves into pairs .
in the first division , the chromosome pairs line up in the centre, the pairs are then pulled apart so each new cell only has one copy of each chromosome, some of the fathers and some of the mothers go into each new cell .
in the second division , the chromosomes line up in the centre of the cells
the arms of the chromosomes are ulled apart .
you get four gametes each with a single set of chromosomes in it.
each gamete is genetically different from the others because the chromosomes all get shuffled up during meiosis and each gamete only gets half od them at random .
29
what are the differences between mitosis and meiosis
mitosis produces clones
meiosis produces variation
mitosis produces 2 identical diploid daughter cells
meiosis produces 4 different haploid cells
mitosis is for asexual reproduction
meiosis is for sexual reproduction - to produce gametes
30
why is variation among offspring good
it increases the chance of a species surviving a change in the environment .
while a change in the environment could kill some individuals , it is likely that variation will have led to some of the offspring being able to survive in the new environment - they have survivial advantage .
31
what is natural selection
is a process where organisms that are better adapted to an environment will survive and reproduce. This means that the advantageous alleles. of this variant organism are passed on to offspring.
32
what is selective breeding and how can we use it
we can use it to speed up natural selection
it allows us to produce animals with desireable characteristics .
it is where individuals with desired characteristics are bred to produce offspring that hae the desireable characteristic too .
this means we can increase food production .
33
what are the advantages of asexual reproduction over sexual reproduction
there only needs to be one parent
uses less energy as organisms dont need to find a mate
faster
many identical offspring can be produced in favourable conditions
34
what is malaria caused by
a parasite that is spread by mosquitoes
35
how does the parasite malaria reproduce in mosquitoes and on the human host
reproduces sexually when in the mosquitoe
asexually when in the human host
36
how do fungus reproduce
release spores which become new fungi when they land in a suitable place.
spores can be produced sexually and asexually.
asexually produced spores dorm fungi that are genetically identical to the parent fungus .
sexually produced spoes introduce variation and are often produced in response to an unfavourable change in the environment , increasing the chanve that the population will survive a change.
37
how do plants reproduce(asexually or sexually )
give examples
both
asexual reproduction takes place in different ways - strawberry plants produce runners / these are stems that grow horizontally on the surface of the soil away fro a plant. at various points a new strawberry forms that is identical to the original plant.
plants that grow bulbs - new bulbs can form from the main bulb and divide off . each new bulb can grow into a new identical plant
38
what pair of chromosome decides your sex
23rd pair
labelled XY or XX
39
what chromosomes do males have and what chromosomes do females have
males havve X and Y
the Y chromosome causes male characteristics
Females have two X chromosomes
the XX combination allows female characteristics to develop
40
what is the percent chance of a sperm carrying an x or y chromosome
50 %
41
what is an allele
different versions of the same gene
42
how many alleles of every gene do you have
2 - one on each chromosome in a pair
43
what is homozygous and what is heterozygous
two alleles for a particular gene that are the same - homozygous
two alleles for a particular gene that are different - heterozygous
44
what are the two tyoes of alleles and how are they represented
dominant - the characteristic that is shown - represented with a capital letter
recessive - - represented with a lowecase letter
45
what is a genotype and what is a phenotype
the combination of alleles you have - genotype
characteristics shown - phenotype
46
how many recessive allele do you need to display the recessive characteristic
both alleles must be recessive
47
what are males and females represented by on a family tree
male - square
female - circle
48
what is cystic fibrosis
a genetic disorder of the cell membranes that results in the body producing a lot of thick sticky mucus in the air passages and the pancreas
49
what allele causes cystic fibrosis
recessive
1 in 25 carry it
people with only one coppy of the allele wont have the disorder - they are carriers
for a child to have the disorder, both parents must be either carriers or have the disorder themselves
50
what is polydactyly
a genetic disorder where a baby is born with extra fingers or toes .
51
what allele is polydactyly caused by
dominant allele
it can be inherited if just one parent carries the defective allele
52
what is embryo screening
during IVf embryos are fertilisedin the lab
before being implanted it is possible to remove a cell from each embryo and analyse its genes
many genetic disorders can be detected this way
it is also possible to get DNA from an embryo in the womb and test that for disorders
53
what are the arguments for and against embryo screening
against :
it implies that people with genetic problems are undesireable - this could increase prejudice
there may come a point where everyone wants to screen their embryos so they can pick the most desireable one
screening is expensive
for :
it will help to stop people suffering
treating disorders costs the government a lot of money
there are laws to stop it going too far .
at the moment parents cannot even select the sex of their baby
54
who was gregor mendal
an austrian monk who trained in mathematics and natural hisotory at the university of vienna
55
what had mendal discovered
he had shown that the height characteristic in pea plants was determnied by seperately inherited hereditary units passed on from each parent .
the ratio of tall and dwarf plants in the offspring showed that the unit for tall plants was dominant over the unit for dwarf plants.
he reached three important conclusions about heredity in plants :
characteristics in plants are determined by hereditory 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 an individual has both the dominant and the recessive unit for a characteristic , te dominant characteristic will be expressed
56
why was the importance of mendals work not realised straight away
they didnt have the background knowledge to properly understand his findings - they didnt know about genes , DNA and chromosomes .
57
using medals work , how have the obsercations of many different scientists contributed to the understanding of genes that we have today
in the late 1800s , scientists became familiar with chromosomes
they were able to observe how they behaved during cell division
in the early 20th centrury , scientists realised that there were striking similarities in the way what chromosomes and medels units acted. based on this it was prposed that the units were found on the chromosomes. know we know these units as genes .
in 1953 the structure of dna was determines
this allowed scientists to go on and find out exactly how genes work
58
what are the two types of variation
genetic variation
environmental variation
59
what is environmental variation
differences between individuals that are not inherited but caused by the environment that the organism lives in,
e.g. a plant in lots of sun will be strong and green whereas with no sun it will have yellow leaves
environmental variation cover a wide range of differences
60
what do most characteristics depend on
a mix of genetic and environmental factors
e.g. maximum height an animal or plant could grow is determined by its genes . but whether it actually grows that tall depends on its environment
61
what is the theory of evolution
all of todays organisms have evolved from simple lifeforms that first started to develop over three billion years ago .
succesful organisms are more likely to reproduce and pass on genes for characteristics that made them succesful to their offspring .
the organisms less well adapted would be less likely to survive and reproduce so they are less likely to pas on their genes to the next generation
over time beneficial characteristics become more common in the population and the species changes
62
what is survival of the fittest
organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive
63
why was darwins theory not perfect
the relevant scientific knowledge wasnt available at the time
he couldnt give a good explanation for why new characteristics appeared or how individual organisms passed on beneficial adaptations to their offspring
64
what is speciation
over a long time , the phenotype of organisms can change so much because of natural selection that a completely new species is formed .
it happens when populations of the same species change enough to become reproductively isolated - this means that they cant interbreed to produce fertile offspring
65
what are reasons for why species go extinct
the environment changes too quickly -e.g. destruction of habitat
a new predator kills them all - e.g. humans hunting them all
a new disease kills them all
they cant compete with another species for food
a catastrophic event happens that kills them all - a volcanic eruption or a collision with an asteroid
66
why was charles darwin's idea of evolution very controversial
it went against common religious beliefs about how life on earth developed -it was the first plausible explanation for the existence of life on earth without the need for a creator .
darwin couldnt explain why these new useful characteristics appeared or how they were passed on from individual organisms to their offspring . but then he didnt know anything about genes or mutations - they werent discovered untill 50 years after his theory was published .
there wasnt enough evidence to convince many scientists because not many other studies had been done into how organisms change over time .
67
what was jean babtiste lamarks idea about evolution
argued that changes that an organism aquires during its lifetime will be passed on to its offspring - e.g. he thoguh that is a characteristic was used a lot by an organisms then it would become more developed during its lifetime and the organisms offspring would inherit the aquired characteristics .
68
was lamarks hypothesis accepted or rejected
rejected as his experiments didnt support his hypothesis
69
why might scientists develop different hypothesis
have different beliefs
influenced by different people
think differently
70
is darwins theory of evolution accepted or rejected and why
accepted
discovery of genetics supported his idea because it provided an explanation of how organisms born with beneficial characteristics can pass them on .
other evidenceas found by looking at fossils of different ages. - this allows you to see how changes in organisms developed slowly over time . the relatively recent discovery of how bacteria are able to evolve to become resistant to antibiotics also further supports evolution by natural selection
71
what is selective breeding
when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population ,
organisms are selectively bred to develop features that are useful or attractive
72
what tyoe of things do we use selective breeding for
animals that produce more meat or milk
crops with disease resistance
dogs with a good ,gentle temperament
decorative plants with big or unusual flowers
73
what can selective breeding be used for in agriculture
to improve yields
74
what is the basic process of selective breeding
from your existic stock , select the ones which have the characteristics your after
breed them with each other
select the best of the offspring , and breed them together
continue this process over several generations and the desireable trait gets stronger and stronger . eventually all the offspring will have the characteristic .
75
what is the disadvantage of selective breeding
reduces the gene pool - the number of different alleles in a population
this is because the farmer keeps breeding from the best animals or plants which are closely related - this is inbreeding
76
what is the issue with inbreeding
can cause health problems because there is more chance of the organism inheriting harmful genetic defects when the gene pool is limited .
some dog breeds are particularly susceptible to certain defects because of inbreeding
there can also be serious problems if a new disease appears because there isnt much variation
77
what is genetic engineering and how does it work
transfer a gene responsible for a desired characteristic from one organisms genome into another organism so that it also has the desired characteristic ,
a useful gene is isolated from one orangisms genome using enzymes and is inserted into a vector .
the vector is usually a virus or a bacterial plasmid . depending on the type of organisms that the gene is being transfered to .
when the vector is introduced to the target organism , the useful gene is inserted into its cell .
78
what do scientists use genetic engineering for
bacteria have been genetically modified to produce human insulin that can be used to treat diabetes
genetically modified crops have had their genes modified e.g. to improve yield or resistance to disease, insects and herbicides
sheep have been genetically engineered to produce substances like drugs in their milk that can be used to treat human diseases
scientists are researching genetic modification treatments for inherited diseases caused by faulty genes e.g. by inserting working genes into people with the disease- this is gene therapy
79
what stage of life do wetransfer genes for genetic engineering
n the early stage of development so that the organism develops with the characteristic coded for by the gene
80
what are the pros and cons of GM crops
cons
some people say that growing GM crops will affect the number of wild flowers that live in and around the crops - reducing farmland biodiversity .
not every one is convinced that GM crops are safe and some people are concerned that we might not fully understand the effects of eating them on human health . e.g. peoplea re worried they may develop food allergies to the food .
transplanted genes may get out into the natural environment . e.g. the hebicide resistant gene may be picked up by some weeds creating a new superweed variety.
pros
can increase yield
can be engineered to contain nutrients that epople are missing e.g. golden rice with betacarotene - lack of this causes blindness
GM crops are being grown in places without any problems
81
how can plants be cloned by tissue culture
plant cells are pt into a growth medium with hormones and they grow into new plants - clone of the parent plant
these lants can be made very quickly in very little space and be grown all year
tissue culture is used by scientists to preserve rare plants that are hard to reproduce naturally and bu plant nurseries to produce lots of stock quickly .
82
how can plants be cloned from cuttings
gardeners can take cuttings from good parent plants and then plant them to produce genetically identical copies of the parent plant .
these plants can be produced quickly and cheaply . this is an older , simpler mthod that tissue culture
83
how can you make animal clones using embryo transplants
farmers can prpduce cloned offspring from their best bull or cow
sperm cells are taken from a prize bull and egg cells are taken from aprize cow .
the sperm are then used to artificially fertilize and egg cell .
the embryo that develops is then split many times before any cells become specialised
these cloned embryos can then be implanted into lots of other cows where they grow into baby calves ( which are genetially identical to each other )
hundreds of ideal offspring can be produced every year from the best bull and cow .
84
how does adult cell cloning work
involves taking an unfertilised egg cell and removing its nucleus
the nucleus is then removed from an adult body cell and is inserted into the empty egg cell.
the egg cell is then timulated by an electrical shock - this makes it divide just like a normal embryo
when the embryo is a ball of cells , it is implanted into the womb of an adult female
it grown into a genetically identical copy of the original adult body cell as it has the same genetic infornmation
this was used to create dolly - the first famous cloned sheep .
85
what are the issues surrounding cloning
results in a reduced gene pool - fewer different alleles in a population - if a population are closely relateed and a new disease appears , they could be wiped out - there may be no allele in the population giving resistance to it.
cloned animals may not be as healthy as normal ones - dolly the sheep had arthiritis which tends to occur in older sheep
some people worry that humans may be cloned in the future
86
what are the advantages of animal cloning
could lead to greater understanding of the development of the embryo and of ageing and age related disorders .
could be used to preserve endangered species .
87
what are fossils and what can they tell us
the remains of organisms from may thousands of years ago which are found in rocks
they provide the evidence that organisms lived ages ago .
fossils can tell us a lot about how much or how little organisms have chaged over time .
88
what are three ways that fossils form in rocks
from gradual replacement by minerals
things like teeth shells bones which dont decay easily can last a long time when buried
they are eventually replaced by minerals as they decay , forming a rock like substance shaped like the original hard part.
the surrounding sediments also turn to rock but the fossil stays distinct inside the rock and eventually someone digs it up .
from casts and impressions
sometimes, fossils are formed when an organisms is buried in a soft material like clay .
the clay later hardens around it and the organisms decays , leaving a cast of itself .
an animals burow or a plants roots can be preserved as casts
from preservation in places where no decay happens
in amber ( clear telllow stone made from fossilised resin ) and tar pits there is no oxygen or moisture so decay microbes cant survive .
in glaciers it is too cold for the decay microbes to work
peat bogs are too acidic for decay microbes
89
what are the different hypotheses suggesting how life first came into being
why cnat these be supported or disproved
maybe the first life forms came into existance in a primordial swampy ( or under the sea ) here on earth .
maybe simple organic molecules were brought to earth on comets - these could have then become more complex organic molecules and eventually very simple life forms
lack of good valid evidence
many early life forms were soft bodied and soft tissues tend to decay away completely - so the fossil record is incomplete
fossils that did form millions of years ago may have been destroyed by geological activity
90
what is a species
a group of similar organisms that can reproduce to give fertile offspring .
91
what is speciation
the development of a new species
speciation occurs when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
92
what is isolation
where a population of a species are seperated
this can happen due to a physical barrier
conditions on either side of the barrier will be slightly different
because the environment is different on each side , different characteristics will become more common in each population due to natural selection operating differently on the populations
93
who is alfred wallace and what is he known for
a scientist working with charles darwin
one of the early scientists working on the idea of speciation
he independantly came up with the idea of natural selection and published it with charles darwin
observatinos he made as he travelled the world provided evidence to support the theory of evolution by natural selection
e.g. he realised warning colurs aer used by some species to deter predators from eating them .
94
how can bacteria become anti biotic resistant
bacteria sometimes develop random mutations
this can lead to changes in the bacterias characteristics
tjhis can lead to antibiotic resistant strains forming as the gene for antibiotic resistance becomes more common in the population .
because they are so rapid at reproducing , they evolve quickly .
95
why is the ability for bacteria to resist antibiotics a huge advantage for them
allows them to survive longer and reproduce more
this increses the population size of the antibiotic resistant strain
96
what is the issue with antibiotic resistant strains of bacteria
people infected with the bacteria arent immune to the new strain and there is no effective treatment.
this means the infection spreads easily between people
sometimes drug companies come up witha new antibiotic that is effective but superbugs that are resistant to most known antibiotics are becoming more common .
MRSA is a common superbuf that is really hard to get rid of and can be fatal if it enters the bloodstream
97
what are examples of innapropriate uses of antibiotics
doctors prescribing them for non serious conditions or infections caused by viruses
98
why is it important that people take the full course of antibiotics they are prescribed
makes sure that all of the bacteria are destroyed which means that there are none left to mutate and develop into antibiotic resistant strains .
99
what can antibiotics be used for in farming and why might this be an issue
can be used to prevent animals becoming ill and to make them grow faster.
this can lead to antibiotic resistant bacteria in the animals which spread to humans .
increasing the concern about overuse of antibiotics has led to some countries restricting their use
100
the increase in antibiotic resistance has encouraged drug companies to work on developing ne antibiotics - why is this process dificult
expensive
rate of development is slow
we are unlikely to keep up with demand for new drugs
101
who came up with teh linnaean system , when , and what is it
carl linnaeus - 1700s
living things are divided into kingdoms
the kingdoms are sub divided into smaller and smaller groups - phylum , class, order, family ,genus, species
102
who came up with the three domain system , when , what is it
carl woese
199-
divided organisms into three large groups called domains
archaea - organisms in this domain where once thoufht to be primitive bateria , but they are actually a different type of prokaryotic cell . they were first found in extreme places suchas hot springs and salt lakes .
bacteria - this domain contains true bacteria likek e coli and staphylococcus . although they often look similar to archaea , there are lots of biochemical differences between them
eukaryota - this domain includes a broad range of organisms including fungi, plants,animals and protists
these are then divided into smaller groups ,, kingdom ,phylum ,class,order,family,genus,species
103
what is the binomial system
every organisms is given a two part latin name
the first part refers to the genus that organism belongs to .
this gives you info aobout the organisms ancestry. the second part refers to the species
the binomial system is used worldwide and means that scientists in different countries or who speak different languages all reer to a particular species by the same name
104
what are evolutionary trees
show how scientists think different species are related to each other
they show common ancestors and relationships between species the more recent the common ancestore the more closely related the two species are
scientists analyse lots of different types of data to ork out evolutionary relationships .
for living organisms they use the current classification data
for extinct species they use info from the fossil record
