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inheritance, variation and evolution Flashcards

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Biology 101 flashcards
1
Q

meiosis vs mitosis in terms of identicality

A

meiosis leads to non-identical cells being formed while mitosis leads to identical cells being formed

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2
Q

what does sexual reproduction involve

A

the fusion of male and female gametes
- sperm and egg cells in animals
- pollen and egg cells in flowering plants

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3
Q

how does sexual reproduction work

A

there is a mixing of genetic information which leads to variety in the offspring. the formation of gametes involves meiosis

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4
Q

how does asexual reproduction work

A

only one parent and no fusion of gametes, resulting in no mixing of genetic information. this leads to genetically identical offspring (clones).
- mitosis in eukaryotes
- binary fission in prokaryotes

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5
Q

what does gametes being haploid mean

A

they have half the genetic material of a somatic (normal) body cell. i.e., in humans, gametes have 23 chromosomes, while a normal body cell has 46 chromosomes

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6
Q

where does meiosis occur

A

in the reproductive organs, i.e., the testes and ovaries, to form gametes

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7
Q

what happens when a cell divides to form gametes

A
  • copies of the genetic information are made
  • the cell divides twice to form four gametes, each with a single set of chromosomes
  • all gametes are genetically different from eachother
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8
Q

how does fertilisation restore the full number of chromosomes

A

the fusion of a male and female gamete during fertilisation forms a zygote, which is a diploid cell with 2 sets of chromosomes

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9
Q

what happens after fertilisation

A

the fertilised egg (zygote) will divide by mitosis to produce genetically identical cells, forming an embryo. as the embryo develops, cells differentiate

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10
Q

advantages of sexual reproduction

A
  • produces variation in the offspring
  • if the environment changes, variation gives a survival advantage by natural selection
  • natural selection can be sped up by humans in selective breeding to increase food production
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11
Q

advantages of asexual reproduction

A
  • only one parent needed
  • more time and energy efficient as do not need to find a mate
  • faster than sexual reproduction
  • many identical offspring can be produced when conditions are favourable
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12
Q

disadvantages of asexual reproduction

A
  • no variation
  • susceptible to environmental change
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13
Q

disadvantages of sexual reproduction

A
  • reliant on sperm and egg coming into contact
  • slower than asexual reproduction
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14
Q

how do malarial parasites reproduce

A

asexually in the human host, but sexually in the mosquito

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15
Q

how do fungi reproduce

A

asexually by spores but also reproduce sexually to give variation

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16
Q

how do plants reproduce

A

they produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils

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17
Q

what is DNA

A

a polymer made up of two strands forming a double helix. it’s contained in structures called chromosomes in the nucleus

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18
Q

define a gene

A

a small section of DNA on a chromosome

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19
Q

what does each gene code for

A

a particular sequence of amino acids to make a specific protein

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20
Q

define a genome

A

the genome of an organism is the entire genetic material of that organism

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21
Q

use of the human genome

A

the whole human genome has now been studied and this will have great importance for medicine in the future

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22
Q

importance of understanding the human genome

A

1) helps us search for and identify genes that are linked to certain diseases, e.g., genes that increase risk of cancer
2) helps us understand and treat lots of inherited disorders like CF
3) it can be used to trace human migration patterns from the past by comparing genomes from people all around the world in order to help people discover their ancestry

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23
Q

define a nucleotide

A

monomers made of phosphate, a common sugar and a base that make up DNA

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24
Q

four DNA bases

A

A, C, G and T

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25
Q

what is the code for a particular amino acid

A

a sequence of three bases; the order of bases controls the order in which amino acids are assembled to produce a particular protein

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26
Q

what is the DNA polymer made up of

A

repeating nucleotide units

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27
Q

what do the long strands of DNA consist of

A

alternating sugar and phosphate sections. attached to each sugar is one of the four bases

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28
Q

what results in a change in DNA structure

A

it may result in a change in the protein synthesised by a gene

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29
Q

define a mutation

A

a random change in the DNA base sequence

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30
Q

what happens if a mutation has an effect

A

a few mutations code for an altered protein with a different shape. this means an enzyme may no longer fit the substrate binding site or a structural protein may lose its strength

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31
Q

describe the effect of mutations

A

they occur continuously, but most do not alter the protein, or only alter it slightly so that its appearance or function is not changed

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32
Q

what are non-coding parts of DNA

A

the parts of DNA that do not code for specific proteins

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33
Q

what do non-coding areas do

A

they can switch genes on and off, therefore if a mutation occurs in a non-coding section, this may affect how genes are expressed. this means cells could produce wrong proteins at wrong times, which could cause uncontrolled mitosis leading to cancer

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34
Q

define an allele

A

a different version of the same gene

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35
Q

define a chromosome

A

a strand of DNA that contains many genes

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36
Q

define a gamete

A

a sex cell

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37
Q

define dominant

A

the allele that is always expressed in the phenotype as long as there is one copy present

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38
Q

define recessive

A

the allele that is only expressed in the phenotype if there are two recessive alleles present

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39
Q

define homozygous

A

when a person has 2 copies of the same allele

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40
Q

define heterozygous

A

when a person has 2 different alleles

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41
Q

define genotype

A

a combination of alleles

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42
Q

define phenotype*

A

the genotype expressed

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43
Q

how do the alleles (or genotype) present operate

A

they operate at a molecular level to develop characteristics that can be expressed as a phenotype

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44
Q

what are most characteristics a result of

A

multiple genes interacting, rather than a single gene

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45
Q

what are inherited disorders

A

disorders caused by the inheritance of certain alleles

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46
Q

what is cystic fibrosis

A

an inherited disorder of cell membranes caused by a recessive allele (sufferer must be homozygous recessive)

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47
Q

what does cystic fibrosis cause

A

produces thick, sticky mucus in the respiratory and digestive systems, making breathing difficult and causing digestive problems

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48
Q

symptoms of cystic fibrosis

A

breathlessness, coughs, repeated chest infections

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49
Q

why does cystic fibrosis lead to low weight gain

A

the mucus produced clogs the pancreatic duct and blocks enzyme secretion. results in poor digestion, causing low weight gain

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50
Q

genotype of carrier and sufferer for cystic fibrosis

A

carrier: Cc
sufferer: cc

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51
Q

what is polydactyly

A

an inherited disorder of genetic sequencing caused by a dominant allele

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52
Q

what does polydactyly cause

A

in an abnormal number of fingers and toes

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53
Q

genotype of carrier and sufferer for polydactyly

A

carrier: you can’t be a carrier of polydactyly
sufferer: Pp or PP

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54
Q

what is embryo scanning

A

taking cells from embryos so that their DNA can be analysed to see if the embryo has the alleles for inherited disorders

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55
Q

disadvantages of embryonic screening

A
  • expensive for the NHS; money could be spent elsewhere
  • a large number of embryos are created but only a small number are implanted, meaning that healthy embryos with the potential for life are destroyed
  • gives rise to designer babies, where we only screen for desirable features, which is also unethical
  • miscarriage risk
  • screening can give false positive or negative result
  • parents of children with genetic disorders that have a good quality of life may argue that it’s unethical
  • can be a painful procedure
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56
Q

fully describe chorionic villus sampling (embryo scanning)

A
  • sample of placental tissue taken through wall of abdomen or vagina
  • done at 10-12 weeks
  • 1-2% miscarriage risk
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57
Q

fully describe amniocentesis

A
  • needle inserted into the amniotic fluid to collect cells from placenta and foetus
  • done at 15-16 weeks
  • 0.5-1% miscarriage risk
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58
Q

what is pre-implantation genetic screening used for

A

for use in IVF before the embryo is implanted

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59
Q

describe how pre-implantation genetic screening works

A
  • eggs are fertilised to produce embryos
  • embryos analysed for genetic defects
  • only healthy embryos are injected into uterus
  • mother gives birth to genetically healthy baby
60
Q

two purposes of screening for genetic disorders

A
  • to check that they haven’t been passed onto the embryo
  • to prepare for aiding the child e.g., buying specialised medical equipment
61
Q

advantages of embryonic screening

A
  • allows you time to prepare things like specialised medical equipment if the child is a sufferer of a genetic disorder
  • allows you to see whether the developing embryo is a sufferer
  • allows the option of terminating a pregnancy if the couple doesn’t want to give birth to a sufferer
62
Q

what do the pairs of chromosomes do

A

22 pairs control characteristics, but one of the pairs carries the genes that determine sex

63
Q

sex chromosomes in females and in males

A

females: XX
males: XY

64
Q

define variation

A

differences in the characteristics of individuals in a population

65
Q

what can variation be due to

A
  • differences in the genes they have inherited (genetic causes)
  • differences in the conditions in which they have developed (environmental causes)
  • a combination of genes and the environment
66
Q

what usually occurs within a population of a species

A

there is usually extensive genetic variation

67
Q

what do all variants arise from and how does this affect phenotypes

A

all arise from mutations
- most have no effect on the phenotype
- some influence phenotype
- very few determine phenotype

68
Q

what happens if a mutation leads to a new phenotype

A

mutations occur continuously - if the new phenotype is suited to an environmental change, it can lead to a relatively rapid change in the species

69
Q

define evolution

A

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

70
Q

define a species

A

a group of animals that are similar enough to be able to breed successfully together

71
Q

continuous vs discontinuous variation

A

continuous, e.g., leg length, fur length, height, weight

discontinuous, e.g., fur type (straight or curly), eye colour, fur colour

72
Q

what is the theory of evolution by natural selection

A

a theory by Charles Darwin which states that all species of living things have evolved from simple life forms that first developed more than three billion years ago

73
Q

structure of natural variation questions
- use example of a giraffe

A

natural variation/mutation:
mutation led to some [giraffes] having [longer necks]

competition:
when competing for [food], the [giraffes] with [longer necks] have the advantage as they have [greater reach]

survival of the fittest and breeding:
the [giraffes] with [longer necks] are therefore more likely to survive and breed

passing on of genes:
genes for [longer necks] are passed on to offspring

74
Q

what happens if two populations of one species become different

A

if they become so different in phenotype that they can no longer interbreed to produce fertile offspring, they have formed two new species

75
Q

define selective breeding (artificial selection)

A

the process by which humans breed plants and animals for particular genetic characteristics

76
Q

when did selective breeding originate

A

humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals

77
Q

selective breeding framework

A
  • choose parents with the desired characteristics from a mixed population; say which traits are looked for in these
  • breed them together
  • from the offspring, those with the desired characteristic are bred together
  • this continues over many generations until all the offspring show the desired characteristic
78
Q

characteristics for selective breeding to look out for

A
  • disease resistance in food crops
  • animals which produce more meat or milk
  • domestic dogs with a gentle nature
  • large or unusual flowers
79
Q

what can selective breeding lead to and what is this

A

inbreeding - where some breeds are particularly prone to disease or inherited defects

80
Q

problems with selective breeding

A
  • process can be long as there are no guarantees the offspring will have the desired features
  • faster in organisms that produce lots of offspring at once
  • can lead to inbreeding (increased chance of inherited disorders)
  • because a limited number of organisms are used for breeding, this creates less variety in the gene pool, which can lead to inbreeding
81
Q

what did charles darwin propose

A

the theory of evolution by natural selection

82
Q

natural selection framework

A
  • mutation within the population leads to variation
  • competition between individuals
  • individuals with characteristics most suited to the environment are more likely to survive to breed successfully
  • the characteristics that have enabled these individuals to survive are then passed on to the next generation
83
Q

why was the theory of evolution only gradually accepted

A
  • the theory challenged the idea that God made all the animals and plants on Earth
  • there was insufficient evidence at the time the theory was published to convince many scientists
  • the mechanism of inheritance and variation was not known until 50 years after the theory was published
84
Q

what did Lamarck propose

A

changes that occur in an organism during its lifetime can be inherited - we now know that in the vast majority of cases this type of inheritance cannot occur

85
Q

how did wallace and darwin work together

A

wallace independently proposed the theory of evolution by natural selection. he published joint writings with darwin in 1858 which prompted darwin to publish ‘On the Origin of Species’ in 1859

86
Q

explain the work of alfred russel wallace

A

worked worldwide gathering evidence for evolutionary theory - he is best known for his work on warning colouration in animals and his theory of speciation

87
Q

how has the theory of speciation developed over time

A

alfred wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation

88
Q

speciation framework

A
  • geographical separation
  • environmental differences e.g., predators, habitats
  • random mutation leads to variation; difference between the two populations
  • best adapted in each area more likely to survive, breed and pass on alleles and genes
  • eventually the different populations can no longer successfully breed with each other
89
Q

how does a new species arise

A
  • population of organisms separated by some form of barrier e.g., mountain, ocean
  • conditions on each side of the barrier are different
  • long periods of time elapse
90
Q

what phrasing in a question will indicate the use of the speciation framework

A

when ‘common ancestor’ is mentioned

91
Q

define a species

A

a group of animals that are similar enough to produce fertile offspring

92
Q

how can you prove that organisms are of a different species

A

by trying to breed them together - if they do produce offspring but they’re infertile, then the organisms are of a different species

93
Q

why is evidence for darwin’s theory now available

A

as it has been shown that characteristics are passed on to offspring in genes from further scientific research

94
Q

list of evidences for evolution

A
  • looking at the anatomy of animals
  • all cells have a very similar chemistry
  • some organisms can be observed evolving e.g., bacteria (antibiotic resistance)
  • fossil record
95
Q

define fossils

A

the remains of organisms from millions of years ago, which are found in rocks

96
Q

state three ways fossils may be formed

A
  • from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
  • when parts of the organism are replaced by minerals as they decay
  • as preserved traces of organisms, such as footprints, burrows and rootlet traces
97
Q

why can scientists not be certain about how life began on earth + what the first life forms looked like

A

because the fossil record is incomplete. many early forms of life were soft-bodied, which means that they have left few traces behind. what traces there were have been mainly destroyed by geological activity

98
Q

what can we learn from fossils

A

how much or how little different organisms have changed as life developed on earth, and how species may have arisen from common ancestors

99
Q

how do fossils act as partial evidence for the theory of evolution

A

fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms are found in newer rocks

100
Q

what do antibiotics treat

A

bacterial illnesses

101
Q

why can we observe the evolution of bacteria

A

because they reproduce at a fast rate

102
Q

how have antibiotic resistant bacteria evolved

A
  • a mutation of bacterial pathogens produces new strains
  • some strains might be resistant to antibiotics so aren’t killed
  • the non-resistant bacteria that has been killed means there is less competition for nutrients/oxygen between the resistant bacteria
  • the resistant bacteria survive and reproduce, so the population of the resistant strain rises
  • the genes for antibiotic resistance are rapidly passed on to offspring through asexual reproduction via binary fission to their offspring
  • the resistant strain will then spread because people are not immune to it and there is no effective treatment
103
Q

define antibiotic resistance

A

when a bacteria that used to be killed by an antibiotic isn’t affected by it anymore

104
Q

what is MRSA

A

a type of bacteria that is resistant to antibiotics

105
Q

methods for reducing antibiotic resistant bacteria

A
  • doctors shouldn’t 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
  • agricultural use of antibiotics should be restricted
106
Q

why are there increasingly new resistant strains of bacteria

A

because the development of new antibiotics is costly and slow, so it is unlikely to keep up with the emergence of new resistant strains

107
Q

how have living organisms been traditionally classified

A

into groups depending on their structure and characteristics in a system developed by Carl Linnaeus

108
Q

what did carl linnaeus do

A

classify organisms into a hierarchal structure

109
Q

linnaeus’ structure

A

kingdom
phylum
class
order
family
genus
species

Keep Putting Chips On Fat Guys Stomachs

110
Q

how did improvements in microscopes affect the classification system

A

improvements in microscopes allowed internal structures and the understanding of biochemical processes to become more developed, meaning new models of classification were proposed

111
Q

how are organisms named

A

by the binomial system of genus and species

112
Q

what has evidence available from chemical analysis allowed

A

there is now a three-domain system developed by Carl Woese

113
Q

what are organisms divided into in Woese’s system

A
  • archea: primitive bacteria usually living in extreme environments
  • bacteria: true bacteria (no membrane enclosed nucleus)
  • eukaryota: includes protists, fungi, plants and animals
114
Q

what are evolutionary trees

A

a method used by scientists to show how they believe organisms are related

115
Q

how do evolutionary trees work

A

they use current classification data for living organisms and fossil data for extinct organisms

116
Q

advantages of classifying organisms

A
  • makes them easier to study
  • helps us understand how things are related
  • helps us recognise biodiversity
  • gives scientists a common language to communicate with
  • allows us to make sense of the living world
117
Q

when does extinction occur

A

when there are no remaining individuals of a species still alive

118
Q

describe the work of gregor mendel

A

in the mid 19th century, he carried out breeding experiments on plants

119
Q

what was one of mendel’s observations

A

the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged

120
Q

what was discovered in the late 19th century about genetics

A

behaviour of chromosomes during cell division was observed

121
Q

what was discovered in early 20th century about genetics

A

it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways - this led to the idea that the ‘units’, now called genes, were located on chromosomes

122
Q

what was discovered in the mid 20th century about genetics

A

the structure of DNA was determined and the mechanism of gene function worked out

123
Q

how was the gene theory developed

A

by the scientific work of many scientists

124
Q

what does cloning using tissue culture use

A

small groups of cells from part of a plant to grow identical new plants

125
Q

describe how clones from tissue culture are produced

A
  • a few cells are taken and placed on nutrient agar with auxin to promote root and shoot development
  • then planted normally
  • all plants produced are genetically identical to the original plant
126
Q

what are the cloning methods in plants

A

taking cuttings and using tissue culture

127
Q

what is tissue culture important for

A

preserving rare plant species or commercially in nurseries

128
Q

why do you bag plants when cloning

A

to maintain damp and warm conditions

129
Q

briefly describe taking cuttings for cloning

A

an older, but simple, method used by gardeners to produce many identical new plants from a parent plant

130
Q

method for taking cuttings to clone plants

A

cut off a growing side stem, keep in damp conditions (bag it) until roots grow and then plant in soil

131
Q

what are the cloning methods in animals

A

embryo transplants and adult cell cloning

132
Q

method for adult cell cloning

A
  • nucleus removed form unfertilised egg cell
  • nucleus from adult body cell e.g., skin cell, inserted into egg cell
  • electric shock stimulates egg cell to divide to form an embryo
  • embryo cells contain same genetic info as adult skin cell
  • embryo develops into ball of cells
  • inserted into uterus of adult female to continue its development
133
Q

what does embryo cloning involve

A

splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers

134
Q

method for embryo cloning

A
  • fertility hormones given to chosen female animal to produce many eggs
  • sperm from selected male animal used to fertilise female’s eggs by artificial insemination
  • early embryos develop and gently washed out of female’s uterus
  • embryo split apart into individual cells (not specialised atp)
  • each cell develops into embryo and transplanted into host surrogate mothers; prepared for pregnancy by hormones
  • genetically identical clones born. babies not biologically related to host mothers
135
Q

pros of adult cell cloning

A
  • helps save animals from extinction
  • can bring back animals from extinction
  • can clone prized animals
  • help infertile couples
  • clone pets
136
Q

cons of adult cell cloning

A
  • clones reduce genetic diversity
  • fears about cloning human babies
  • making clones of yourself
137
Q

define genetic engineering

A

modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

138
Q

what have plant crops been genetically engineered for

A

to be resistant to diseases or to produce bigger better fruits

139
Q

what have bacterial cells been genetically engineered for

A

to produce useful substances such as human insulin to treat diabetes

140
Q

process of genetic engineering

A
  • enzymes used to isolate required gene; gene is cut out and inserted into a vector, usually bacterial plasmid or virus
  • vector is used to insert gene into required cells
  • genes transferred to cells of animals, plants or microorganisms at early stage in their development so that they develop with desired characteristics
141
Q

where are the genes inserted to in plants and what are they used for

A

desired genes often inserted into meristem cells which used to produce identical clones of genetically modified plant

142
Q

pros of genetic engineering

A
  • improved plant growth rates
  • increased crop food value
  • ability to grow crops in adverse conditions
  • ability to produce plants that make own pesticide
  • herbicide-resistant crops
143
Q

how could genetic engineering potentially cure genetic disorders

A

‘healthy’ genes inserted into affected cells, making them work properly. this changes the affected gene so no longer have disorder

144
Q

cons of genetic engineering

A
  • relatively new; long-term effects unknown
  • insects may develop resistance to pesticides by eating foods gm to produce pesticides
  • cost of genetically engineered products too high for farmers
  • gm crops previously been made infertile so farmers buy new seed each year
  • infertile genes in gm crops may spread into wild plants
  • people could start to genetically modify humans or the genes of future children
145
Q

protein synthesis transcription stage

A

1) base sequence of gene copied into complementary template molecule (mRNA) - DNA too large to leave nucleus
2) mRNA passes out of nucleus and into cytoplasm

146
Q

protein synthesis translation stage

A

1) mRNA attaches to ribosome
2) amino acids brought to ribosome on carrier molecules (tRNA)
3) ribosome reads triplet of bases on mRNA and uses this to join together correct amino acids in correct order
4) when protein chain is complete, folds into unique shape
5) shape determines function of the protein

147
Q

protein synthesis order of stages

A

transcription -> translation

bio spec (9 decks)

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