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a level biology > 3.4 Genetic Information, Variation And Relationships Between Orgainisms > Flashcards

3.4 Genetic Information, Variation And Relationships Between Orgainisms Flashcards

1
Q

What is the size order of the components of the genetic code?

A

Gene, DNA, chromosome, nucleus

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2
Q

What is DNA?

A

Deoxyribonucleic acid, polymer made up of nucleotide monomers

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3
Q

What is prokaryotic DNA like?

A

DNA molecules are short, circular and not associated with proteins

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4
Q

What is eukaryotic DNA like?

A

Found in the nucleus, DNA molecules are very long, linear and associated with proteins called histones. together a DNA molecule and it’s associated proteins form a chromosome

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5
Q

What is a loci?

A

A gene occupies a fixed position, called a locus, on a particular DNA molecule

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6
Q

What is a chromosome?

A

DNA that is coiled up very tightly, 23 pairs, consist of maternal and paternal chromosomes, cells with 24 pairs are called diploids

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7
Q

What is a gene?

A

A short section of DNA that codes for one polypeptide

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8
Q

What is an allele?

A

A different version of a gene

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9
Q

What is meant by homologous?

A

Same structural features and pattern of genes but not identical (contain different alleles)

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10
Q

What can the genetic code be described as?

A

Non overlapping, a triplet code, universal

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11
Q

What is meant by the genetic code being a triplet code?

A

One triplet codes for one amino acid, three nucleotide bases= one amino acid

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12
Q

What is meant by the genetic code being universal?

A

Each triplet code always coded for the same amino acid, it is the same in all living organisms

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13
Q

What is meant by the genetic code being non overlapping?

A

Each base is discrete (123,456 not 123,234,345)

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14
Q

What is meant by degeneracy?

A

64 possible triplet codes and only 20 different amino acids in proteins, some amino acids coded for by more than one triplet (e.g tyrosine=TAT or TAC), act as punctuation marks, indicate start and stop (start codon=ATG)

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15
Q

What is protein synthesis?

A

Transcription (formation of pre mRNA in the nucleus) and translation (formation of polypeptides at the ribosomes)

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16
Q

What is the difference between mRNA and DNA?

A

mRNA has the bases GCAU whereas DNA has GCAT, mRNA has ribose DNA has deoxyribose, mRNA is single stranded, DNA is double helix, DNA has the base pairing G+C and A+T the but mRNA has no base pairing (can predict the percentage of bases in DNA but not in mRNA), mRNA is shorter than DNA

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17
Q

Describe the process of transcription:

A

Firstly DNA helicase breaks the hydrogen bonds between the bases in the DNA double helix, free RNA nucleotides complementary base pair with the template strand forming weak hydrogen bonds, the RNA polymerase will resynthesise the sugar phosphate back bone, it must be RNA polymerase because the DNA polymerase is not specific to the ribose sugar, the weak hydrogen bonds between RNA bases and the template strand break resulting in pre mRNA, the template strand re forms hydrogen bond with the other DNA strand, pre mRNA is then splices to remove non coding DNA (introns) and joins together coding DNA (exons) so mRNA only contains coding DNA and it is small enough to leave the nucleus via nuclear pores

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18
Q

What is translation?

A

The process by which mRNA is used to make a specific protein

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19
Q

Describe the process of translation:

A

mRNA leaves the nucleus through nuclear pores, mRNA associated with the ribosome fitting between the two sub units of the ribosome, one codon of the mRNA is read by a tRNA molecule, the tRNA brings an amino acid to the codon and attaches to it by a complimentary anticodon, the ribosome moves along the mRNA strand and another complementary tRNA molecule attaches to the next codon, two amino acids at the ribosome join by a peptide bond during a condensation reaction, the first tRNA molecule can move back into the cytoplasm to pick up a new amino acid, this process continues until a stop codon is reached (no amino acid or complementary anticodon available), energy released from ATP hydrolysis is used to form the polypeptide chain and fold it into its specific 3D shape

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20
Q

Why is splicing not necessary in prokaryotes?

A

mRNA is produces directly from the DNA, there are no introns in prokaryotic DNA

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21
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of the bases in DNA, they are random, spontaneous, natural and either positive or negative

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22
Q

What are the three types of mutation?

A

Insertion, deletion and substitution

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23
Q

What is meant by insertion?

A

An extra base is added, affects the amount whole strand, every triplet code changes as there is a frameshift

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24
Q

What is meant by deletion?

A

Remove a base, affects the whole strand, a nucleotide is lost from the DNA sequence, causes a frame shift

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25
Q

What is substitution?

A

Only affects one triplet code as one base is replaced, has the least effect as only only one amino acid is affected or none at all if it is degenerate

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26
Q

What is meant by frameshift?

A

Every amino acid after the insertion or deletion will move one place

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27
Q

What is a mutagen?

A

A physical or chemical agent that changes the genetic material of an organism

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28
Q

What are examples of mutagenic agents?

A

Caffeine, X-rays, mustard gas, UV radiation

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29
Q

What is chromosomal mutation?

A

Changes in the structure or number of whole chromosomes e.g. polyploidy and non disjunction

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30
Q

What is polyploidy?

A

Changes in the structure or number of the whole chromosome, cells have multiple sets of chromosomes, 3n=triploid which is common in plants

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31
Q

What is non disjunction?

A

Homologous pairs fail to separate, down syndrome = extra chromosome 21

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32
Q

What is meiosis?

A

The process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)

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33
Q

Describe what happens in meiosis:

A

After interphase is he genetic material is replicated so there is two chromatids per chromosome , in prophase 1 genetic material condenses and the nuclear membrane breaks down, in metaphase 1 chromosomes associated in homologous pairs line up on the equator attached to spindle fibres at the centromere, in anaphase 1 spindle fibres contract and homologous chromosomes are pulled to opposite poles, in telophase 1 and cytokinesis the nuclear envelope reforms, cytoplasm splits and the cell membrane forms. The same process occurs in meiosis two (the second division) the same process occurs except this time the cells are only 2n and spindle fibres attach at the centromere to pull apart sister chromatids and haploid cells are formed (n).

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34
Q

What are the two forms of genetic variation?

A

Crossing over (the exchange of alleles) and independent segregation (random arrangement of chromosomes)

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35
Q

What is meant by genotype?

A

The genetic make up of an organism, the genes and alleles they have

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36
Q

What is meant by phenotype?

A

The observable characteristics, genotype and the environment affect this

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37
Q

What are the three causes of genetic variation?

A

Mutations, sexual reproduction, meiosis

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38
Q

What happens in crossing over (meiosis)?

A

Homologous pairs of chromosomes line up, chromatids of each pair become twisted, section of chromatid breaks off and rejoins chromatid of the other homologous chromosome, sections of chromatids exchanged, sections have different alleles, new combinations of linked alleles cause variation

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39
Q

What is independent segregation?

A

Gregor Mendel in the 19th century said genes are inherited independently of one another BUT genes close together have a high likelihood of being inherited together, this occurs during anaphase

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40
Q

What happens in independent segregation?

A

Homologous pairs of chromosomes line up along the equator completely randomly, therefore the combination of chromosomes pulled to each pole is random, meaning daughter cells produced are genetically different as the genes are the same but alleles are different. Chromatids are then separated in meiosis 2

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41
Q

How do you predict how likely genetic variation is? (formula)

A

(2^n)^2

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42
Q

Why can’t you predict the genetic variation from crossing over?

A

Because it is random

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43
Q

Why can you predict the variation from independent segregation and sexual reproduction?

A

Either chromatid making up a homologous pair could be pulled into one or two piles (independent segregation 2^n) and gamete come together during sexual reproduction ((2^n)^2)

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44
Q

What is meant by genetic variation?

A

The total number of different alleles in a population, occurs due to mutations, there must first be a change in the DNA (a random mutation) resulting in a difference

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45
Q

Explain how a mutation results in a change in characteristic (4 marks)

A

First a mutation occurs which is a random change in the DNA, this caused a change in the triplet code and therefore the codons in mRNA, this means that different anticodon on tRNA will make a different sequence of amino acids and therefore a different polypeptide. Changes the secondary, tertiary and quaternary structure, changes the protein formed/its function. This results in increased genetic diversity

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46
Q

Why is genetic diversity important?

A

Within a species all genes are the same but they still have genetic diversity, total number of genetic characteristics differs because there are different alleles present, high genetic diversity = large number of different alleles, low genetic diversity = small number of different alleles

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47
Q

What are the positives of high genetic diversity?

A

Less spread of disease, more complex food web, more likely to survive in different conditions e.g. adapting for climate change prevents extinction and increases stability, can survive in different habitats prevents overcrowding and competition

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48
Q

What are negatives of high genetic diversity?

A

Less have the desirable characteristics i.e food for humans and selective breeding, fewer organisms adapted to an environment at a specific time or place

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49
Q

What is meant by phenotype?

A

Observable characteristics that an organism has I.e. blue eyes or brown eyes affected by genetics and environment

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50
Q

What is meant by genotype?

A

Genetic make up of an organism (eye colour, beak size)

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51
Q

What is meant by natural selection

A

Not all alleles are equally likely to be passed to the next generation, the better adapted to the environment tend to survive and breed at the expense of those less well adapted, changing the allele frequency

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52
Q

What is meant by allele frequency?

A

The number of times an allele occurs within a gene pool

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53
Q

What is meant by gene pool?

A

The total number of alleles in a particular population at a specific time

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54
Q

Explain how natural selection occurs

A

Random mutation of alleles within the gene pool may result in a new allele of a gene which could code for a characteristic which is advantageous over other phenotypes in the environment. These individuals will be better adapted and there’s more likely to survive in their competition with others. These individuals therefore survive and breed at the expense of individuals without this mutation. The offspring are more likely to inherit the new allele which is advantageous and they in turn are more likely to survive and so reproduce successfully. Over generations the number of individuals with the new advantageous allele will increase at the expense of individuals without this, over time the frequency of the new advantageous allele in the population will increase while that of the non advantageous ones decreases

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55
Q

How does a change in the environment affect selection?

A

The change in the environment does not cause the mutation it just makes it more advantageous

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56
Q

What is a normal distribution curve?

A

No bias, data surrounds central point (mean,median and mode are all the same/central), curve is symmetrical, curve is bell shaped

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57
Q

Why is there still variation (50% above mean and 50% below mean) in a normal distribution curve?

A

Most characteristics are a result of multiple genes (polygenes), each gene is affected by the environment, changes in the environment = changes in the mean

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58
Q

What happens on directional selection?

A

Mutation occurs, change in environment occurs, selection favours one direction from the mean, the mean characteristic of the population changes, one extreme is selected for, allele frequency changes

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59
Q

How is antibiotic resistance in bacteria a result of directional selection?

A

A random mutation occurs in the gene pool resulting in a different or new allele coding for antibiotic resistance as a different protein/enzyme is produced to break down the antibiotic. The introduction of antibiotics into the environment means that this mutated characteristic has become advantageous meaning that these bacteria have a higher chance of survival and reproduction at the expense of bacteria without this mutation. This means that offspring are more likely to inherit this characteristic, increasing the allele frequency, moving the mean, median and mode toward the extreme of having high antibiotic resistance

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60
Q

What is stabilising selection?

A

The mean median and mode have not changed, but there is a higher frequency of the mean, median and mode and a lower frequency at the extremes

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61
Q

Why does stabilising selection occur?

A

The environment is stable so it is more advantageous for the population to mostly have the characteristics suited to that environment, selection acts against both extremes in a range of phenotypes, mean is favoured, phenotypic variation is reduced, environment has remained stable

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62
Q

Why is birth weight an example of stabilising selection?

A

Both extremes selected against, low extreme; the weak to survive, can’t retain heat, vulnerable to predators, need more food (parent has to hunt and leave child alone). High extreme; complications with birth/mother could die during childbirth, taking more resources from mother, more pressure on organs

63
Q

What phenotype is selected in directional selection?

A

Extreme

64
Q

What phenotype is selected in stabilising selection?

A

Median/mean/mode

65
Q

What is the effect of directional selection on the characteristic of a population?

A

Mean characteristic shifts

66
Q

What is the effect of stabilising selection on the characteristics of a population?

A

Mean characteristic stays the same

67
Q

What is the shape of the distribution curve for directional selection?

A

Normal distribution curve, bell shape, remains the same but shifts to left or right

68
Q

What is the shape of the distribution curve for stabilising selection?

A

Steep incline, peak increase, range decreases, mean does not change

69
Q

What is the example for directional selection?

A

Antibiotic resistance

70
Q

What is the example for stabilising selection?

A

Birth weight

71
Q

What is aseptic technique?

A

Method designed to prevent contamination from microorganisms

72
Q

When do you need to go work aseptically?

A

Handling surgical equipment, surgery, during labour, inserting catheters or IV drips

73
Q

What structural features do bacteria have?

A

Capsule, cell wall, cell membrane, plasmids, (flagella), 70S ribosomes, cytoplasm, chromosomal DNA

74
Q

Why don’t antibiotics target animal cells?

A

Antibiotics target the bacterial cell wall, animal cells don’t have these so won’t be affected

75
Q

What is a species?

A

a group of individuals that are capable of breeding to produce living and fertile offspring

76
Q

what are the three different types of adaptation?

A

anatomical, physiological, behavioural

77
Q

what is anatomical adaptation?

A

changes in the appearence of the organism e.g. small ears in cold environments

78
Q

what is physiological adaptation?

A

how the inside of the body is adapted (chemical reactions/processes) e.g. camels oxidising fat for water

79
Q

what is behavioural adaptation?

A

the actions of the organism to protect themself, e.g swallows migrating from the UK to Africa

80
Q

what are binomial names?

A

how organisms are named universally, written in italics or underlined, new species are given two names e.g. Panthera pardus

81
Q

what is the first name in binomial naming?

A

generic name, denotes the genus, upper case

82
Q

what is the second name in binomial naming?

A

specific name, denotes the species, used to identify, lower case

83
Q

what is the binomial naming system?

A

kingdom, phylum, class, order, family, genus, species

84
Q

what are courtship displays?

A

making yourself more appealing to a mate e.g. peacocks pluming their feathers, bright coloured males, bird songs/dances, making noises, penguins building piles of rocks

85
Q

what are the different types of courtship displays?

A

vocalisation, displays of beauty or strength, ritualised movements i.e. dances

86
Q

what is the stimuli feedback loop for courtship displays?

A

stimuli: the male communicates a courtship signal -> this acts as a visual stimulus and is detected by receptors -> the CNS coordinates a response -> effector contracts or releases a hormone -> effector causes a specifi innate/stereotyped behaviour of her own (response) -> acts as a stimulus to the male -> the male responds

87
Q

why are courtship behaviours important?

A

enables an organism to recognise one of their own species, identify if a mate is capable of breeding, forming pair bonds (life long pairs), synchronising mating seasons

88
Q

why is it important that/ how courtship behaviours enable an organism to recognise one of their own species?

A

to produce fertile offspring, prevents cross breeding, ensures genes are passed on, use similarities in physical characteristics and behaviours

89
Q

why is it important that courtship behaviours identify if a mate is capable of breeding?

A

both partners need to be sexually mature, fertile and receptive to mating, females may only be in season once a year

90
Q

why is it important that courtship behaviours help form pair bonds?

A

ensures successful breeding (more investment), successful raising of the offspring/pass on genes

91
Q

why is it important that courtship behaviours identify synchronising mating seasons?

A

determines whether the female is in a receptive (fertile) state, correct female response then mating will take place

92
Q

What are the three domains?

A

Archea, bacteria and eukaryotes

93
Q

What is meant by classification?

A

The organisation of living organisms into groups

94
Q

What is taxonomy?

A

The theory and practice of biological classification, proposed by Carl Linnaeus, it is not random and is based on accepted principles

95
Q

What are the two forms of taxonomy?

A

Artificial and phylogenetic

96
Q

What is meant by analogous?

A

Have the same function but do not have the same evolutionary origin

97
Q

What is artificial classification?

A

based on analogous characteristics, not based on evolutionary relationships, e.g. bat and butterfly, shark and penguin

98
Q

What is phylogenetic classification based on?

A

Classified based on shared features, characteristics derived from ancestors, based on evolutionary relationships, based on homologous characteristics

99
Q

What is meant by homologous?

A

Similarly evolutionary origins/structures regardless of their function

100
Q

What is phylogenetic classification?

A

Arranges groups of organisms into a hierarchy, smaller groups within larger groups, no overlaps between groups, each group is called a taxon (taxa), based on their ancestory/evolutionary relationship, creates binomial names

101
Q

What are domains?

A

The highest taxonomic rank, developed by Carl Woese

102
Q

What are the key characteristics of bacteria?

A

Murein cell wall, free floating DNA, plasmids/circular DNA, 70S ribosomes; smaller, no membrane bound organelle, uni cellular, some are pathogens

103
Q

What are the key characteristics of archea?

A

Single celled prokaryotes, similar shape/size to bacteria, DNA/genes and protein synthesis like eukaryotes, no murein in cell wall, no membrane bound organelle

104
Q

What are the key characteristics of eukarya?

A

Nucleus, 70s and 80s ribosomes, cellulose cell wall (plants), DNA is linear associated with proteins called histones, usually multi cellular, split into four kingdoms protoctista, fungi, plantas, animals

105
Q

What are the four eukaryote kingdoms?

A

Protoctista, fungi, plantas, animals

106
Q

What is a phylogenetic tree?

A

Phylogenetic relationships are displayed in tree like diagrams, oldest ancestral species at the base, most recent divergence at the ends of branches

107
Q

What are the advantages of using observable characteristics for classification?

A

Easy to do/quick, anyone could do it, does not require advanced equipment

108
Q

What are the disadvantages of using observable characteristics for classification?

A

Can’t see underlying features, observations are subjective, can’t see patterns of inheritance, fossil data hard to find, genes can be polygenetic, might result from the environment

109
Q

How does studying DNA base sequences lead to more accurate groupings if species?

A

Compare the exact order of nucleotides on the DNA, mutation occurs causing a difference between individuals, more differences= fewer similarities so individuals are more distantly related

110
Q

How does studying mRNA sequences lead to more accurate groupings?

A

mRNA complementary to DNA, differences in mRNA, differences in mRNA= differences in DNA, more differences= more distantly related

111
Q

How can studying amino acids sequence in proteins lead to more accurate groupings of species?

A

Differences in DNA= differences in mRNA= differences in amino acids

112
Q

What are the advantages of studying DNA and mRNA for classification?

A

More specific so can see degenerate codes, determine the exact order of bases

113
Q

What are the disadvantages of studying DNA and mRNA for classification?

A

Smaller so requires more advanced equipment which is expensive, time consuming to look at every base

114
Q

What are the advantages of studying amino acids for classification?

A

Determines the DNA and mRNA sequences

115
Q

What are the disadvantages of studying amino acids for classification?

A

Can cost a lot, timely, DNA may be non coding, can’t see degeneracy

116
Q

What is meant by genetic diversity?

A

Total number of different alleles

117
Q

What is meant by hybrid?

A

Combined two different elements

118
Q

What is DNA hybridisation?

A

Direct comparisons between the DNA sequences of different organisms

119
Q

What is the process of DNA hybridisation?

A

DNA from two species is heated to denature the DNA and break the hydrogen bonds, strand A given radioactive labels, strand A and B are mixed, cool to allow renaturation of double stranded DNA, determine degree of hybridisation; complete= identical, partial=related, none=unrelated

120
Q

How can immunology be used to identify similarities between proteins?

A

Serum containing non-self human antigens is injected into a species such as rabbit which will respond by producing anti-human antibodies which are complimentary to human antigens. The rabbit serum containing the anti-human antibodies is then added to serum of other species. If a high percentage of anti human antibodies form precipitate with antigens in the serum of other species, it is closely related to the human

121
Q

Why are species such as rabbits used in immunology to identify similarities between proteins?

A

They are small/easy to produce/breed/keep/maintain

122
Q

Why can’t immunology be used to identify similarities in genetic sequences?

A

Because they could produce the same proteins but different base structure because of degeneracy, variation in other proteins may differ

123
Q

What is meant by biodiversity?

A

The range and variety of genes, species and habitats within a particular region

124
Q

What is meant by genetic diversity?

A

When different alleles are present throughout a population, high genetic diversity means organisms are more adaptable, with a large food chain, where disease won’t spread easily

125
Q

What is meant by species diversity?

A

The number of different species and the number of individuals of each species within only one community

126
Q

What is meant by ecosystem diversity?

A

The range of different habitats within a particular area

127
Q

How was genetic diversity studied?

A

By calculating species diversity using species richness (the number of different species in a particular area at a given time)

128
Q

What do you need to know to calculate species diversity?

A

The number of different species in an area, the proportion of the community made up by each species

129
Q

What is the purpose is Simpson’s diversity index?

A

Quantified how bio diverse an area is

130
Q

What is Simpson’s diversity index?

A

d= N(N-1)
———-
En(n-1)

where d=species diversity n=total number of organisms of each species N=total number of organisms of all species and E= the sum of

131
Q

What is meant by ecosystem stability?

A

The environment changes, all species are the same ( low diversity) all will die, the ecosystem is unable to respond to the change and the ecosystem crashes

132
Q

How does agriculture reduce biodiversity?

A

Monoculture, lack of intercropping, competition for space, use of pesticides and fertilisers, cattle in the field a species may grow, draining wetland and marshes, removing hedge grows

133
Q

Why does monoculture (growing only one species) reduce biodiversity?

A

No biodiversity, directly reducing number of species, indirectly reduce habitat and food

134
Q

How does lack of intercropping (not rotating what is grown each season) reduce biodiversity?

A

Drains nutrients and results in monoculture

135
Q

How does competition for space reduce biodiversity?

A

Less variation of species in an area, outcompeted by dominant

136
Q

How does use of pesticides and fertilisers reduce biodiversity?

A

Pesticides directly kills insects, could get into the water supply which promotes the growth of algae which blocks and light the plants at the bottom, deplete oxygen supply, organisms living in water die (eutrophication)

137
Q

How do you cattle in the field where species may grow reduce biodiversity?

A

Over grazing, trampling , reduction in species (food/habitat)

138
Q

How does draining wetlands and marshes reduce biodiversity?

A

Water needed for photosynthesis, removing nutrients and moisture, can’t grow

139
Q

How does removing hedge grows reduce biodiversity?

A

Removing a habitat and food source

140
Q

What is meant by deforestation?

A

The permanent clearing of forests and the conversion of land to other uses, such as agriculture, grazing or settlement

141
Q

How does deforestation reduce biodiversity?

A

50,000 species are being lost each year due to deforestation, loss of species directly, loss of habitats, loss of a food source

142
Q

How does deforestation impact economically?

A

tourist attractions, food could be sold, more expensive to plant new trees and keep the trees already there, agriculture, pollinators, commercial products, medicine

143
Q

How can deforestation be controlled?

A

Give farmers incentives E.G.money, taxes, deforestation charges, plant more new trees, eco charges

144
Q

What is meant by intraspecific variation?

A

Variation within a species such as eyecolour or blood-group

145
Q

What is meant by interspecific variation?

A

Variation between a species such as food source or pollinator

146
Q

What are the examples of quantitated methods for measuring biodiversity?

A

Quadrat and transects

147
Q

what is meant by sampling bias?

A

biased choices made by the investigator, deliberate or unwillingly, sample is unrepresentative, avoided by random sampling

148
Q

what is meant by chance variation?

A

even if bias is avoided chance variation can occur, not representative sample, i.e. individuals are the same (e.g. all samples on one side, may get more/less light)

149
Q

what is a quadrat?

A

square frame used to investigate biodiversity in one area or to compare two areas

150
Q

what is a transect?

A

line measured at equal intervals to establish a key pattern in biodiversity

151
Q

how can you avoid sampling bias?

A

pick random area using a coordinate generator

152
Q

how can you avoid chance variation?

A

take multiple measurements and calculate the mean

153
Q

how do you calculate standard deviation?

A

the square root of the sum of (measured value-mean value) squared divided by total number of values in sample - one

154
Q

what happens between transcription and translation?

A

, pre mRNA is then splices to remove non coding DNA (introns) and joins together coding DNA (exons) so mRNA only contains coding DNA and it is small enough to leave the nucleus via nuclear pores

a level biology (21 decks)

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