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GCSE Biology > Inheritance, Variation and Evolution COPY > Flashcards

Inheritance, Variation and Evolution COPY Flashcards

1
Q

what is DNA?

A

a chemical that all of the genetic material in a cell is made up from, containing coded information, basically all the information needed to put an organism together and make it work

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2
Q

what does DNA stand for?

A

Deoxyribonucleic acid

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3
Q

where is DNA found?

A

the nucleus of animal and plant cells in really long structures called chromosomes, which normally come in pairs

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4
Q

describe the structure of DNA

A

a polymer - made up of two strands coiled together in the shape of a double helix

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5
Q

what is a gene?

A

a small section of DNA found on a chromosome

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6
Q

what does each gene code for?

A

a particular sequence of amino acids which are put together to make a specific protein

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7
Q

how many amino acids are used to code for how many proteins?

A

20 amino acids used to code for thousands of proteins

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8
Q

what does DNA determine about a cell?

A

what kind of protein it makes (eg haemoglobin, keratin ) and that in turn determines what type of cell it is ( eg red blood cell, skin cell)

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9
Q

what is a genome?

A

a term meaning the entire set of genetic material in an organism

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10
Q

how does the understanding of the human genome help us understand and combat disease?

A
  • it allows scientists to identify genes in the human genome that are linked to different types of disease
  • knowing which genes are linked to inherited diseases could help us to understand them better and could help us develop effective treatments for them
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11
Q

“scientists can look at the genomes to trace the migration of certain populations of people around the world”

elaborate on this point :D

A

All modern humans are descended from a common ancestor who lived in Africa, but humans can now be found all over the planet.
The human genome is mostly identical in all individuals, but as different populations migrated away from Africa, they gradually developed tiny differences in their genomes.
By investigating these differences, scientists can work out when new populations split off in a different direction, and what route they took

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12
Q

DNA is a POLYMER what is the name for the repeating units in this polymer?

A

nucleotides

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13
Q

describe DNAs nucleotides structure …

A 
each nucleotide consists of:
- one sugar molecule
- one phosphate molecule
- one 'base'
The sugar and phosphate molecules in the nucleotides form a 'backbone' to the DNA strands. The sugar and phosphate molecules alternate. One of four different bases joins together each sugar. Each base links to a base on the opposite side in the helix.
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14
Q

what are the 4 bases that hold the nucleotides together?

A

A, T, C, and G

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15
Q

what are the complimentary base pairs?

A

A & T , C & G

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16
Q

what do the order of bases in a gene determine?

A

the order of amino acids in a protein

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17
Q

each amino acid is coded for by a sequence how many bases per gene?

A

3 bases

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18
Q

what do non-coding parts of DNA do?

A

switch genes on and off, and so control if the gene is expressed

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19
Q

what does it mean if a gene is expressed?

A

if a gene if used to make a protein or not

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20
Q

where area proteins made?

A

cytoplasm anf ribosomes

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21
Q

how do ribosomes make proteins?

A

they use the code in the DNA. The DNA is found in the cell nucleus and cannot move out of it because its too big, so the DNA is transported from the nucleus to the ribosomes using a transport molecule called mRNA.

mRNA copies the code from the DNA, the mRNA acts as a messenger betweed the DNA and the ribosome - carrying the code between the two

the correct amino acids are brought to the ribosomes in correct order by carrier molecules

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22
Q

what does a proteins unique shape mean?

A

it determines which task the protein is made to perform

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23
Q

give some examples of proteins…

A

enzymes - biological catalysts to speed up chemical reactions
hormones - used to carry messages around the body
structural proteins - physically strong ( eg collagen strengthens connective tissues)

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24
Q

what is a mutation?

A

a random change in an organisms DNA

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25
Q

give an example of a spontaneous mutation?

A

when a chromosome is not replicated properly

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26
Q

how can the chances of a mutation occurring increase?

A

by exposure to certain substances or some types of radiation

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27
Q

what happens when a mutation occurs?

A

the sequence of DNA bases in the gene change which produces a genetic variant . SAS the sequence of DNA bases codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for

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28
Q

how do mutations effect a protein?

A
  • most mutations have very little, or no effect on the protein, some will change it to such a small extent that its function or appearance is unaffected
  • some mutations seriously affect a protein, because sometimes the mutation will code for an altered protein with a change in its shape, causing it to lose its ability to perform its function
  • mutations in non-coding DNA can alter how genes are expressed
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29
Q

explain how a change in shape of a protein ( due to mutation) could affect its ability to perform its function…

A
  • if the shape of the enzymes active site has changed it’s substrate may no longer be able to bind to it
  • structural proteins like collagen could lose their strength if their shape is changes, meaning they can no longer provide structure and support
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30
Q

what are the 3 types of mutations?

A

insertions, deletions and substitutions

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31
Q

what is an insertion mutation?

A

where a new base is inserted into the DNA base sequence where it shouldn’t be, so an insertion changes the way the groups of three bases are ‘read’, which can change the amino acids that they code for - they change more than one amino acids as they have a knock-on-effect on the bases further on in the sequence

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32
Q

what is a deletion mutation?

A

when a random base is deleted from a DNA sequence, like insertions they change the way that the base sequence is read and have knock of effects further down the sequence

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33
Q

what is sexual reproduction?

A

where genetic information from two organisms ( a father and mother) is combined to produced offspring which are genetically different to either parent

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34
Q

what do mother and father cells produce in meosis?

A

gametes - eg egg and sperm cells in humans

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35
Q

how many chromosomes does a human gamete have?

A

23 chromosomes - half the number of chromosomes in a normal cell ( instead of having two of each chromosome, a gamete has just one of each)

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36
Q

what happens to the egg and sperm cell in sexual reproduction?

A

they fuse together to form a cell with the full number of chromosomes

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37
Q

why is there variation of the offspring of sexual reproduction?

A

it receives genetic information from both its parents, so inherits different features

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38
Q

what is asexual reproduction?

A

reproduction that only involves one parent, and produces genetically identical offspring

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39
Q

how does asexual reproduction happen?

A

mitosis - an ordinary cell makes a new cell by dividing in two

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40
Q

what is it called when a cell is genetically identical?

A

a clone ;)

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41
Q

what kind of organisms reproduce asexually?

A

bacteria, plants and animals

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42
Q

in humans where are the only 2 places that meiosis takes place ?

A

ovaries in female and testes in men

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43
Q

what happens in a cell before it starts to divide in meiosis?

(replication, arrangement)

A

the cell duplicates its genetic information, forming two armed chromosomes - one arm of each chromosome is an exact copy of the other arm. After replication, the chromosomes arrange themselves into pairs.

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44
Q

describe the division stages of meiosis

division

A
  • in the first division the chromosome pairs line up in the centre of the cell
  • the pairs are then pulled apart so each new cell only has one copy of each chromosome. Some of the fathers chromosomes and some of the mothers chromosomes go in each cell
  • in the second division, the chromosomes line up again in the centre of the cell, the arms of the chromosomes are pulled apart
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45
Q

what is substitution mutation?

A

substitution mutations are when a random base in the DNA base sequence is changed to a different base

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46
Q

describe the gametes produced in meiosis

A

you get four gametes, each with only a single set of chromosomes in it, each of the games is genetetically different from the others because the chromosomes all get shuffled up during meiosis and each gamete only gets half of them, at random

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47
Q

what happens to the gametes produced by meiosis?

A
  • after the two gametes have fused during fertilisation the resulting new cell divides by mitosis to make a cop of itself
  • mitosis repeats itself many times to produce lots of new cells in an embryo
  • as the embryo develops these cells then start to differentiate into different types of specialised cells that make an organism
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48
Q

what advantages does sexual reproduction have over asexual?

A
  • variation in offspring, increasing their chances of surviving a change in environment: survival advantage
  • because animals with characteristics that make them better adapted to the environment has a higher chance of survival, they are more likely to breed c and pass the genes for the characteristics on: natural selection
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49
Q

what can we use to speed up natural selection?

A

selective breeding - where individuals with desirable characteristics are bred to produce offspring that have desirable characteristics too

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50
Q

how could selective breeding be used to increase food production?

A

by breeding animals that produce a lot of meat

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51
Q

what advantages does asexual reproduction have over sexual reproduction?

A
  • only needs to be one parent
  • asexual reproduction uses less energy because organisms don’t have to find a mate
  • asexual reproduction is faster than sexual reproduction
  • many identical offspring can be produced in favourable conditions
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52
Q

explain how a mosquito can reproduce using both types of reproduction

A
  • caused by a parasite that is spread by mosquitoes, and when a mosquito carrying the parasite bites a human, the parasite can be transferred to the human
  • the parasite reproduces sexually in the mosquito and asexually when on the human host
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53
Q

how many PAIRS of chromosomes are there in every human body cell?

A

23 PAIRS ( so 46 chromosomes per cell )

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54
Q

what are the human’s 23 pairs of chromosomes labelled?

A

XY or XX

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55
Q

what is the males 23rd chromosome pair labelled?

A

X and Y ( the y chromosome causes the male characteristics)

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56
Q

whats the female 23rd chromosome pair labelled?

A

XX ( the xx combination allowing the female characteristics to develop )

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57
Q

give some examples of characteristics controlled by single genes?

A

mouse fur colour, red-green colour blindness

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58
Q

all genes exist in different versions - what are these versions called?

A

alleles

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59
Q

how many alleles do we have for every gene in our body?

A

2 versions - one on each chromosome in a pair

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60
Q

what does it mean if an organism is homozygous for a particular trait ?

A

if the organism has two alleles for that particular gene that are the same

61
Q

what does it mean if a gene is heterozygous

A

if two alleles for a particular gene are different

62
Q

what is a dominant allele?

A

in heterozygous the two alleles are different, but only one can determine what characteristic is present - the allele for the characteristics that’s shown is called the dominant allele

63
Q

what kind of letter is used to represent a dominant allele?

A

CAPITAL LETTERS

eg CC or Cc - because the dominant allele overrules the recessive one

64
Q

when does an organism display recessive characteristics?

A

both alleles must be recessive - even if there is one dominant and one recessive the dominant will always overrule the recessive

65
Q

how do we represent recessive alleles?

A

lower caps

eg ‘cc’

66
Q

define genotype?

A

the alleles an organism has for a particular characteristic

67
Q

define phenotype

A

the visible characteristics of an organism that occurs as a result of its genes

68
Q

what is cystic fibrosis?

A

a genetic disorder of the cell membrane, that results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas

69
Q

what allele causes cystic fibrosis?

how common is it to carry this allele?

A

a recessive allele ‘f’ carried by about 1 in 25 people

70
Q

what does it mean if someone is a carrier of cystic fibrosis?

A

if a person has one copy of the allele, and so doesn’t have the disorder ( because it is recessive)

71
Q

what are the chances of a child having the disorder if both parents are the carriers?

A

1 in 4

72
Q

what is polydactyly

A

a genetic disorder where a babys born with extra fingers or toes

73
Q

what kind of allele is polydactyly caused by?

A

Dominant ‘D’ - so can be inherited if just one parent carries the defective allele

74
Q

what are the chances a child will develop polydactyly if one parent has a ‘D’ allele?

A

50%

75
Q

how is an embryo in IVF genetically screened?

A

they remove a cell and analyse its genes

76
Q

how is a baby genetically screened before it is born?

A

DNA is removed from the embryo in the womb and that can be tested for disorders

77
Q

give some reasons against embryonic screening…

A
  • it implies people with genetic problems are ‘undesirable’ which could lead to an increase in prejudice
  • it may come to the point where everyone wants to screen their embryos to find the most ‘desirable’ one
  • screening is expensive
78
Q

give some reasons for embryonic screening…

A
  • it will help people to stop suffering

- there are laws to stop it going far, eg cannot select sex of their baby

79
Q

who was gregor mendel?

A

an austrian monk who trained in maths and natural history, he noticed that characteristics in palnts were passed on from one generation to the next - his findings once published became the foundation of genetics

80
Q

what were the 3 important conclusions Mendel reached about heredity in plants?

A
  1. Characteristics in plants are determined by ‘hereditary units’
  2. hereditary inits are passed on to offspring unchanged from both parents, one unit from each parent
  3. hereditary units can be dominant or recessive - if an individual has both the dominant and recessive unit the dominant characteristic will be expressed
81
Q

why couldn’t people initially properly understand mendels findings?

A

because they had no idea about genes, DNA or chromosomes

82
Q

around when did scientists become familiar with chromosomes?

A

late 1800s

83
Q

in the early 20th century what did scientists realise about mendels findings?

hint: think about his “units” and chromosomes

A

there was string similiarities between the way mendedls “units acted” and chromosomes, which led to the proposition that these “units” were found on the chromosomes - we now know that these units as genes

84
Q

when was the structure of DNA discovered? why was this important?

A

1953 - allowed scientists to find out how genes work

85
Q

what is variation?

A

when organisms of a species appear slightly different

86
Q

what are the 2 types of variation?

A

genetic and environmental

87
Q

what causes genetic variation?

A

where genes are passed on in gametes from the mother and father, which contains genes that code for your characteristics - meaning you will have some similar characteristics as both parents

88
Q

give some examples of characteristics that are only contained by genes?

A

eye colour, blood group, inherited disorders

89
Q

what causes environmental variation?

A

the conditions that organisms live and grow in causing differences between members of the same species

90
Q

most characteristics are controlled by a mix of what kind of factors?

A

genetic and environmental

91
Q

how do mutations introduce variation?

A
  • mutations are changes to the sequence of bases in the DNA
  • mutations can cause changes in the protein that a gene codes for
  • most mutations have no effect on the organisms phenotype
  • some have a small influence on phenotype and so alter the characteristics slightly
  • in rare occasions mutations can result in a new phenotype being seen in a species
92
Q

if the environment changes and a new phenotype if formed to make the individual more suited to the new environment how may this impact the whole species?

A

it can become common throughout the species relatively quickly due to natural selection

93
Q

what is the definition of the theory of evolution

A

all of todays species have evolved from simple life forms that first started to develop over 3 billion years ago

94
Q

who formed the the theory of evolution?

A

charles darwin - through a world trip, experiments, discussions, new knowledge of fossils and geology to suggest the theory of evolution by natural selection

95
Q

what did Darwin initially know? (foundation)

A
  • organisms in a species show wide variation in their characteristics ( phenotypic variation)
  • organisms have to compete for limited resources in an ecosystem
96
Q

part of Darwins conclusions was the theory of survival of the fittest, what does this mean?

A

the organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive

the successful organisms that survive are more likely to reproduce and pass on the genes for the characteristics that made them successful to their offspring

the organisms that are less well adapted would be less likely to survive and reproduce so they are less likely to survive and reproduce so they are less likely to pass on their genes to the next generation

97
Q

what is the long term effect of the survival of the fittest?

A

beneficial characteristics become more common in the population and the species changes - it evolves

98
Q

why did Darwin’s theory of survival of the fittest not make complete sense when first created?

A

the relevant scientific knowledge wasn’t available at the time, so he couldn’t give a good explanation for why new characteristics appeared or how individual organisms passed on beneficial adaptations to their offspring

99
Q

what knowledge do we have now that supports Darwins’s theory of survival of the fittest?

A

we know that phenotype is controlled by genes, and new phenotypic variations arise because of genetic variations produced by mutations. Benefical variations are passed on to future generations in the genes that parents contribute to their offspring

100
Q

what is the development of a new species called?

A

speciation

101
Q

when does speciation happen?

A

when populations of the same species change enough to become reproductively isolated meaning they can’t interbreed to produce fertile offspring

102
Q

give 5 reasons why a species may become extinct…

A

1) an environment changes too quickly
2) new predator kills them all
3) new disease kills them all
4) cannot compete with other species for food
5) catastrophic event happens that kills them all

103
Q

why was Darwins theory of evolution not accpeted?

A
  • went against common religious events about how life on earth developed
  • Darwin couldn’t explain how the new useful characteristics appeared or how they were passed onto the offspring ( didn’t know anything about genes or mutations)
  • wasn’t enough evidence to convince other scientists
104
Q

what was Jean-Baptiste Lamarck’s scientific theory of evolution?

A

he argued that changes that an organism acquires during its lifetime would be passed on to its offspring, so he thought that if a characteristic of an organism was used lots in its lifetime, then it would become more developed then the organisms offspring would inherit the acquired characteristics

105
Q

how would Jean-Baptiste have explained rabbit offspring that had long legs?

A

he would have thought that the parent rabbits must have used their legs to run a lot ( to escape predators) causing them to get longer - as a result the offspring were born with longer legs

106
Q

why do scientists often have different hypotheses?

A

they may have different beliefs ( eg religous), be influenced by different people, of think in different ways

107
Q

why was Lamarck’s hypothesis eventually rejected?

A

because experiments did not support his hypothesis

108
Q

why did Darwin’s ideas about evolution become an accepted hypothesis - a theory?

A
  • discovery of genetics supported Darwin’s idea as it explained how an organism with benefical characteristics
  • through fossil record evidence
  • antibiotic resistance demonstrates evolution by natural selection
109
Q

what is selective breeding?

A

when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population

110
Q

give some examples of when organisms are selectively bred to develop features that are useful or attractive

A
  • animals that produce more meat or milk
  • crops with disease resistance
  • dogs with good, gentle temperament
  • decorative plants with big or unusual flowers
111
Q

what is the basic process of selective breeding?

A
  1. selects organisms from existing stock which have desired characteristics
  2. breed them with each other
  3. continue process over several generations and desirable traits will get stronger, until all offspring have this trait
112
Q

how can selective breeding be used in agriculture?

A

to improv yields - eg breeding together bulkier cows that produce meat so that over the generations the farmer would get cows with very high meat yield

113
Q

what is the main problem with selective breeding?

A
  • reduces the gene pool, leading to inbreeding
114
Q

why is inbreeding bad?

A

it can cause health problems because there is more chance of the organisms inheriting harmful genetic defects when the gene pool is limited

115
Q

why is a reduction in the gene pool a problem if a new disease appeared?

A
  • because there is not much variation, less chance of any resistant alleles being present in the population
  • all the stock are closely related to each other so if one organism is is killed by the disease then the others are likely to succumb to it
116
Q

what is genetic engineering?

A

the transfer of a gene responsible for a desirable characteristic from one organism’s genome into another organism, so that it also has the desired characteristic

117
Q

what is the basic process of genetic engineering:

A
  • a useful gene is isolated from one organism’s genome using enzymes and is inserted into a vector
  • when the vector is introduced to the target organism the useful gene is inserted into the cell
118
Q

what is a vector in genetic engineering?

A

a virus of bacterial plasmid ( it depends on what type of organism the gene is being transfered to)

119
Q

how have bacteria been genetically modified for use in medicine?

A

bacteria have been genetically modified to produce human insulin that can be used to treat diabetes

120
Q

why crops may be genetically modified?

A

to improve the size and quality of their fruit or to make them resistant to disease, insects and herbicides

121
Q

what are herbicides?

A

chemicals used to kill weeds

122
Q

why may sheeps be genetically engineered?

A

to produce substances like drugs, in their milk which can then be used to treat human disease

123
Q

scientists are currently investigating gene therapy - what does this mean?

A

treating inherited diseases by inserting working genes into people with the disease

124
Q

in genetic engineering sometimes the gene is inserted at an early stage of development ( eg. egg or embryo).. what does this mean about the organisms future development?

A

the organism develops with the characteristic coded for by the gene

125
Q

how may genetic engineering cause a reduction in farmland biodiveristy?

A

it will affect the number of wildflowers and so the number of insects that live in, and around the crops

126
Q

why are people are concerned about genetic engineering?

A
  • they may not be convinced that the GM crops are unsafe, and that we do not fully understand the health risks
  • transplanted genes may get out into the natural environment
127
Q

what may happen if herbicide resistance genes got out into the natural environment?

A

it may be picked up by weeds, creating a variety resistant to weedkillers, their growth could be very hard to control

128
Q

give some positives for of GM crops..

A
  • characteristics chosen can increase the yield, making more food
  • people living in developing nations often lack nutrients and their crops could be modified to contain these
129
Q

what is a tissue culture? what are the advantages and uses?

A
  • a few plant cells put in a growth medium with hormones, so they grow into new plants - clones of the parent plant
  • plants can be made v quickly in v little space, can be grown all yeat
  • tissue culture used by scientists to preserve rare plants that are hard to reproduce naturally
  • used by plant nurseries to produce lots of stock quickly
130
Q

what is the advantages of taking cuttings from good parent plants and planting to create clones of the parent plant?

A
  • quicker, cheaper and simpler
131
Q

how can a farmer produce cloned offspring of a prize bull and cow through embryo transplants

A
  • sperm cells taken from prized bull, egg cells taken from prized cow
  • sperm used to artificially fertilise an egg cell, and the embryo that develops is split many times ( to form clones) before any cells become specialised
  • cloned embryos can then be implanted into other cows where they grow baby calves ( which will be genetically identical to eachother)
132
Q

what does adult cell cloning involve?

A
  1. taking an unfertilised egg cell and removing its nucleus, the nucleus is then removed from an an adult body cell and is inserted into the ‘empty’ egg cell
  2. the egg cell is stimulated by electric shock, making it divide like another embryo
  3. when embryo is only afew cells, it is implanted into the womb of an adult female, and it growa into a gentically identical copy of og adult body cell as it has the same gentic info
133
Q

disadvantages of cloning

A
  • reduced gene pool so less disease resistance
  • cloned animals may not be as healthy as normal ones
  • people worry humans may be cloned in the future
134
Q

advantages of cloning

A
  • quickly gets you lots of ‘ideal’ offspring
  • could be used to help endangered species
  • study of animal clones could lead to better understanding of embryo development and ageing
135
Q

what are fossils?

A

remains of organisms from many thousands of years ago found in rocks

136
Q

in what 3 ways do fossils form in rocks?

A
  1. gradual replacement by minerals ( most fossils occur this way)
  2. from casts and impressions
  3. from preservation in places where no decay happens
137
Q

how do fossils form through gradual replacement by minerals?

A
  • teeth, shells, bones don’t decay easily can last a long time when buried
  • eventually replaced by minerals as they decay forming a rock-like substance shaped like the original hard part
  • surrounding sediments also turn to rock, but the fossils stays distinct inside the rock
138
Q

how do fossils form from casts and impressions?

A
  • sometimes fossils are formed when an organism is buried in a soft material like clay
  • clay later hardens around it and the organism decays leaving a cast of itself
139
Q

what kind of things can be preserved as fossil casts?

A

animal burrows, plant roots, footprints

140
Q

how are fossils formed through preservation in places where no decay happens?

A
  • in amber and tar pits there is no oxygen or moisture so decay organisms cannot survive
  • in glaciers it’s too cold for decay microbes to work
  • peat bogs it is too acidic for decay microbes
141
Q

what are some potential theories for how life first began on earth?

A
  • first life forms may have come into existence in premordial swamp
  • simple organic molecules may have been brought to earth by comets
142
Q

define species

A

a group of similar organisms that can reproduce to give fertile offspring

143
Q

what is speciation

A

the development of new species

144
Q

when does speciation occur

A

when populations of the same species become so different that they can no long successfully interbreed to produce fertile offspring

145
Q

what is natural isolation

A

where populations of a species are separated

146
Q

explain how the process of natural selection is seen in 2 populations isolated from each other die to a natural barrier

A

a natural barrier ( eg earthquake) may geographically isolate some individuals from the main population, conditions on either side of the barrier will be slightly different , so different characteristics will become more common in each population due to natural selection operating differently on the populations

147
Q

explain how isolation and natural selection lead to speciation

A
  • each population ( that has been isolated) shows genetic variation because they have a wide range of alleles
  • in each population individuals with characteristics that make them better adapted to their environment have a better chances of survival and so are more likey to breed successfully
  • alleles to control the benefical characteristics more likely to be passed on to next generation

…. eventually individuals from the different populations will have changed is much they won’t be able to breed with one another to produce fertile offspring - the 2 groups will become: separate species

148
Q

who was Alfred Russel Wallace

A
  • scientist working at same time as darwin
  • one of the early scientists working on idea of speciation
  • wallace independently came up with idea of natural selection but then published idea with darwin
149
Q

what did Wallace famously use for his evidence of natural selection?

A

he realised that warning colours are used by some species to deter predators drom eating them - an example of a benefical characteritic evolved by natural selction

GCSE Biology (8 decks)

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