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a-level bio (aqa) > 4: Genetic information and Variation > Flashcards

4: Genetic information and Variation Flashcards

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1
Q

x

What is a gene?

A

A section of the DNA nucleotides that codes informstion for a polypeptide chain

(A gene occupies a fixed position, called a locus, on a particular strand of DNA)

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2
Q

What are the features of the genetic
code?

A
  • Triplet Code: 3 bases make one amino acid
  • Universal: it is the same in all known living things
  • Non-overlapping: each base appears in only one
    triplet.
  • Degenerate: most amino acids are coded for by more than one
    triplet.
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3
Q

genetic code

What is a triplet code?

A
  • 3 bases = 1 amino acid
  • There are 20 types of amino acids that can make up our proteins.
  • We have 4 base pairs (A, G, C, T) to achieve this:
    If 1 base = 1 amino acid… 4 amino acids
    If 2 bases = 1 amino acid … 16 amino acids
    3 bases = 1 amino acid … code for 64 amino acids (potentially)

This excess of amino acids is important for the next feature…

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4
Q

genetic code

What is a degenerate code?

A
  • most amino acids are coded for by more than one triplet.
  • This is vital to protect against point mutations (change in a single base)
  • Only a few amino acids have just one triplet code e.g. methionine (ATG)
  • The start of a DNA sequence that codes for a polypeptide is always a triplet that codes for the amino acid methionine. If the first methionine molecule does not form part of the final polypeptide it is later removed.
  • There are 3 stop codes (don’t code for any amino acid) and mark the end
    of a polypeptide chain– ATT, ATC, ACT.
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5
Q

genetic code

What is a non-overlapping code?

A
  • each base appears in only one triplet
  • Only read each base once.
  • Evolutionary advantage – mutation may only affect one triplet
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6
Q

genetic code

What is a universal code?

A
  • it is the same in all known living things

e.g. ATG = methionine (same code = same amino acid)

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7
Q

What is an allele?

A

a different version of the same gene (e.g. eye colour)

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8
Q

What is a phenotype and genotype?

A

Phenotype- the characterisic expressed as a result of genetic constitution and its interaction with the environment
Genotype- the genetic makeup of an organism/ genes inherited

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9
Q

What is the difference between dominant and recessive?

A

Dominant- only one allele needs to be inherited for the characteristic to be expressed
Recessive- both alleles needs to be inherited for the characteristic to be expressed

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10
Q

What is the difference between heterozygous and homozygous?

A

homozygous- 2 of the same allele (bb/BB)
heterozyous- 2 different alleles (Bb)

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11
Q

What is DNA like in eukaryotes?

A

In the nucleus of eukaryotic cells, DNA molecules are very long, linear and associated with proteins, called histones. Together a DNA molecule and its associated proteins form a chromosome.
- In eukaryotes, much of the nuclear DNA does not code for polypeptides.
- There are, for example, non-coding multiple repeats of base sequences between genes.
- Even within a gene only some sequences, called exons, code for amino acid sequences.
- Within the gene, these exons are separated by one or more non-coding sequences, called introns.
- Introns can range in size from 10’s of base pairs to 1000’s of base pairs.

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12
Q

Where else can DNA be found in eukaryotes?

A
  • The mitochondria and chloroplasts of eukaryotic cells also contain DNA which is short, circular and not associated with proteins (like prokaryotic cells).
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13
Q

What is DNA like in prokaryotes?

A
  • DNA molecules are short, circular and not associated with proteins. The genetic code may also be overlapping.
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14
Q

What is the genome and the proteome?

A
  • genome- the complete set of genes in a cell
  • proteome- the full range of proteins that a cell can produce
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15
Q

What are the 2 parts of protein synthesis?

A

transcription and translation

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16
Q

What is the role of mRNA in protein synthesis?

A
  • mRNA (messenger RNA)- forms chain of RNA corresponding nthe DNA sequence, read 3 bases at a time
  • made during transcription, synthesised using a DNA template
  • mRNA codon is a sequence of 3 bases, a polynuceotide
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17
Q

What is the role of tRNA in protein synthesis?

A
  • tRNA (transfer RNA) carries amino acids to ribpspmes based on thge bases read (important during translation)
  • carried amino acids from cytoplasm to ribosomes (used to assemble proteins)
  • single polynucleotide, folding to resemble a 3 leaf clover
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18
Q

Transcription

A
  • Hydrogen bonds (between DNA bases) break
  • (Only) one DNA strand acts as a template;
  • (Free) RNA nucleotides align by complementary base pairing
  • (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
  • RNA polymerase joins (adjacent RNA) nucleotides;
  • (By) phosphodiester bonds (between adjacent nucleotides);
  • Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
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19
Q

Translation

A
  • (mRNA attaches) to ribosomes/ (mRNA attaches) to rough endoplasmic reticulum;
  • (tRNA) anticodons (bind to) complementary (mRNA) codons;
  • tRNA brings a specific amino acid;
  • Amino acids join by peptide bonds/ (Amino acids join together) with the use of ATP;
  • tRNA released (after amino acid joined to polypeptide);
  • The ribosome moves along the mRNA to form the polypeptide;
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20
Q

What is transcription?

A
  • a section of DNA is copied into mRNA
  • this section of DNA is often a gene that codes for a protein
  • transcription take place in a eukaryotic nucleus
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21
Q

What are the steps of transcription?

A

1. RNA polymerase attatches to a section of DNA
- RNA polymerase is associated with enzyme DNA helicase which breaks bonds between 2 DNA strands
- the DNA molecule unwinds, exposing a no. of bases
- one DNA strand is used to create a mRNA gene copy (template strand)
2.A mRNA strand is synthesised.
- free RNA bases in the nucleus are attracted to their exposed DNA counterparts.
- hydrogen bonds form between complementary RNA and DNA bases.
- RNA polymerase catalyses the formation of phosphodiester bonds between neighboring RNA molecules, creating a new strand of mRNA.
3.The DNA molecule reforms once RNA has moved past
- Hydrogen bonds reform between DNA bases, causing the double helix to reassemble.
4.RNA polymerase detaches from the DNA once it reaches a stop signal.
- the region at the end of a gene is called a stop signal.
- Once RNA polymerase reaches the stop signal, it ceases to synthesise mRNA and is released from the DNA.
5.mRNA leaves the nucleus through nuclear pores.
- The mRNA will then associate with a ribosome so it can be translated into protein.

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22
Q

What is splicing?

A
  • Eukaryotic DNA contains regions that do not code for a protein. These are called introns.
  • Introns are copied into pre-mRNA during transcription. Introns are removed from pre-mRNA by splicing.
  • During splicing, the introns are removed and the coding regions of mRNA (the exons) are spliced together.
  • The mRNA is now referred to as mature mRNA. The mature mRNA then leaves the nucleus and associates with a ribosome.
  • Prokaryotic DNA does not contain introns. As such there is no mechanism for splicing in prokaryotes.
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23
Q

What occurs during splicing?

A
  • In eukaryotes, transcription results in the production of pre-mRNA; this is then spliced to form mRNA.
  • Eukaryotic genes (unlike prokaryote) contain base sequences that are not translated into polypeptides. Introns are non-coding sections of the gene
  • The Spliceosome forms and causes the introns to form loops which allows the exons to be joined and introns removed.
  • The spliceosome is a complex assembled from small nuclear RNA (snRNA) and proteins.
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24
Q

What is translation?

A

Where proteins are made from the RNA template

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25
Q

What are the steps of translation?

A

1. The mRNA attaches to a ribosome.
- Molecules of tRNA carry amino acids to the mRNA sequence.
- The bond between the tRNA molecule and the amino acid is formed using ATP.
2.The first tRNA anticodon binds to a complementary codon on the mRNA.
- Codons and anticodons will form hydrogen bonds with one another.
- The first tRNA molecule will always bind to the same codon.
- This is called the start codon. In humans it is the sequence AUG.
3.A second tRNA anticodon will attach to the next codon on the mRNA.
- This will occur using the same mechanism as the first tRNA molecule.
4.A peptide bond will form between the neighboring amino acids that are being held by the tRNA molecules.
- The first tRNA molecule will then unbind, leaving its amino acid behind.
5.This cycle will continue, producing a primary chain of amino acids.
- This is the process of elongation.
6.Eventually, the complex will reach a stop codon.
- A stop codon does not code for an amino acid.
- Instead it signals the protein to dissociate from the ribosome and move into a different region of the cell.

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26
Q

What is a mutation?

A
  • a change in genetic material/ nucleic acid base
  • if a mutation occurs in a gene, the sequence of amino acids it codes for and the protein formed could be altered
  • if the base that has been changed still codes for the same amino acid, the protein that is coded for does not change, making it a neutral mutation
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27
Q

What are different types of mutations?

A
  • GENE: substitution, deletion, insertion
  • CHROMOSOMAL: caused by errors in cell division, inversion
  • duplication
  • silent
  • neutral
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28
Q

What are mutagenic agents?

A

This means that the DNA is misread during replication, causing problems with making specific proteins essential to that organism.
Mutagenic agents can cause an INCREASE in the rate of mutations.
e.g.
- Ultraviolet Radiation causing skin cancer
- Cigarette smoke (carcinogen chemicals) causing lung cancer
- Viruses used in gene therapy (good mutations)
- ionising radiation, chemicals and viruses

occur simultaneously

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29
Q

What is a substitution mutation?

A

one base is replaced with another
This means that the sequence for the amino acids has changed which means the sequence will either NOT make the protein the original sequence coded for, make a FAULTY protein, a completely DIFFERENT protein or in most cases, NO protein at all!

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30
Q

What is a deletion mutation?

A

a base is deleted from the sequence
This means that the sequence for the amino acids has changed which means the sequence will either NOT make the protein the original sequence coded for, make a FAULTY protein, a completely DIFFERENT protein or in most cases, NO protein at all!

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31
Q

Why do not all mutations affect the order of amino acids?

A

due to the genetic code being “degenerate”(some amino acids are coded for by more than one DNA triplet code.)
eg. TAT / TAC - both code for the amino acid Tyrosine (substitution)
However, deletions will always lead to a change in base numbers present, which leads to a shift in the base triplets.This is called a FRAMESHIFT

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32
Q

What is an insertion/ addition mutation?

A

A mutation that occurs when a nucleotide (with a new base) is randomly
inserted into the DNA.

  • this changes the amino acid that would have been coded for by the original base triplet, as it creates a new, different triplet of bases
  • an insertion mutation also has a knock-on effect by changing the triplets (groups of three bases) further on in the DNA sequence (frameshift mutation)
  • This may dramatically change the amino acid sequence produced from
    this gene and therefore the ability of the polypeptide to function
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33
Q

What is a chromosome mutation?

A

chromosome mutations are caused by errors in cell division/ meiosis
- In humans, when meiosis works properly then 4 gametes are produced with 23 chromosomes.
- However, when things go wrong with meiosis , the cells produced contain
variations in the numbers of whole chromosomes or pairs of chromosomes.
- this is known as non-disjunction when the chromosomes fail to separate properly.
- Chromosome mutations lead to inherited conditions because the error is present in the gametes.
- Eg. Downs Syndrome (an extra 21 chromosome)

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34
Q

What is a inversion mutation?

A

during crossing over in meiosis, the gene is cut in two places and then inserts “backwards” at 180 °.
- This means a large portion of the gene is backwards, affecting a large proportion of amino acids, meaning non-functional protein could be coded for.

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35
Q

What is a duplication mutation?

A

when awhole gene or section of a gene is duplicated so that two copies of the gene/section appear on the same chromosome
- The original version of the gene remains intact and therefore the mutation is not harmful
- Overtime, the second copy can undergo mutations which enable it to develop new functions
- Duplication mutations are an important source of evolutionary change
- Alpha, beta and gamma haemoglobin genes evolved due to duplication mutations

CAN BE ADVANTAGEOUS

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36
Q

What is a silent/ neutral mutation?

A

A form of point mutation resulting in a codon that codes for the same or a different amino acid but without any functional change in the protein product

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37
Q

What are advantages of some mutations?

A
  • Mutations have been responsible for antibiotic resistance in bacteria, sickle cell resistance to malaria, and immunity to HIV, among others.
  • An Ecuadorian community with the rare gene mutation known as Laron syndrome are protected against cancer and diabetes.
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38
Q

What are disadvantages of some mutations?

A
  • Many other diseases, such as cancer, diabetes and asthma, are linked to genetic mutations.
  • Genetic disorders such as Down’s Syndrome, Prader-willi syndrome, Cystic fibrosis are all caused by chromosomal mutations or gene mutations.
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39
Q

What is genetic diversity?

A

the total no. of different alleles in a population, making it more or less likely that the individuals react to environmental change.

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40
Q

What is population and species?

A

population- a group of individuals of te same species that live in the same place and can interbreed
species- one or more population with the same genes that can produce fertile offspring

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41
Q

What is a selection pressure/ force?

A
  • environmental factors that affect the chance of survival of an organism
  • selection pressures increase the chance of individuals with a specific phenotype surviving/ reproducing over others
42
Q

What is good about organisms with favoured phenotypes?

A
  • individuals with favoured phenotypes have a higher fitness (higher ability to survive and pass on good alleles to offspring).
  • higher fitness= better suited to the environment
43
Q

What are benefits of genetic diversity?

A
  • a population with a large gene pool/ high genetic diversity has a strong ability to adapt to environmental change
  • if a population has a small gene pool/ very low genetic diversity then they are less able to adapt to environmental changes and are vulnerable to extinction
44
Q

What are the links between genetic diversity and survival?

A
  • large gene pool
  • high genetic diversity
  • more alleles
  • larger variety of phenotypes
  • better suited phenotype
  • positive selection pressure
  • more likely of surviving with advantageous characteristic
  • pass on characteristic to offspring
45
Q

What is natural selection?

A

the mechanism of evolution where environmental features apply a selctive force/ pressure and where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.

46
Q

Who came up with the theory of natural selection?

A
  • Charles Darwin (1835)
  • visited Galapagos Islands
  • different mutations occur causing variation within specues
  • published ‘the origin of species’ in 1859
  • the re-examining of the natural selection with modern day knowledge (e.g. genetics) is called Neo-Darwinism
47
Q

How does natural selection occur?

A
  1. random genetic mutations can create multiple alleles of genes within a population (gene pool)
  2. genetic variation within a population createsn intraspecific competition
  3. individuals with particular alleles are better able to face challenges imposed by the environment
  4. individuals possessing alleles which code for advantageous characteristics will be more likely to survive as these characteristics may enable them ti better ibtain resources, grow more rapidly or have a greater response against disease
  5. individuals that survive are more likely to reproduce and pass on the advantageous allele to the next generation
  6. therefore, over time, the frequency of the advantageous allele increases in the population
48
Q

What is meiosis?

A
  • a type of cell division that produes 4 genetically varied haploid daughter cells
  • 2 parts (meiosis 1 and 2)
  • meisosis 1 has interphase, meiosis 2 doesnt
  • I (G1,S,G2),P,M,A,T
49
Q

Regular mitosis

What happens in meiosis 1?

A
  1. Interphase
    chromosomes present as chromatin, DNA replicates and new organelles/ macromolecules are manufactured ready for cell division
  2. Prophase I
    chromosomes condense and become shorter. homologous chromosomes come to lie close together in synapsis (paired chromosomes are called bivalents). identical pairs of sister chromatids are the result of DNA replication that occur during interphase.
    each group of 4 methods is a tetrad held together by centromere
    chiasma form (2 chromatids crossed) over to crossover and exchange genetic material causing Gene variation
  3. Metaphase I
    bivalents (tetrads) become aligned in the center of the cell and are attached to spindle fibers.
    the orientation of each pair of chromosomes on the spindle is a random event and provide a second source of genetic variation
  4. Anaphase I
    Spindle activity separates homologous chromosome pairs and the homologous pairs of chromosomes migrates to opposite cell poles
  5. Telophase I
    spindle fibres disintegrate and the nuclear membranes reform
    in animal cells membrane constricts down the middle of the cell and two identical daughter cells are formed in cytokinesis
    each daughter cell has one member from each homologous chromosome pair
50
Q

What happens in meiosis 2?

A
  1. Prophase II
    2 cells have one member from each pair of homologous chromosomes and are diploid cells
    during late prophase 2 the nuclear membranes disintegrate again and spindle fibers begin to form
  2. Metaphase II
    chromosomes (each with two sister chromatids) line up independently along the equator of the spindle
    meiosis 2 separates the sister chromatids and to distribute them into the four products of meiosis
  3. Anaphase II
    centrioles replicate allowing chromatids to repel each other
    spindle activity pulls chromatids to opposite cell poles making them chromosome
  4. Telophase II
    in animal cells there’s a constriction across the middle and each cell then divides into two
    this results in four haploid daughter cells each possessing one member from each pair of the original chromosomes
    as a result 4 genetically different cells are produced
51
Q

What processes lead to genetic variation in gametes?

A
  • CROSSING OVER- during prophase one of meiosis the non-sister chromatids are so closely associated they become intertwined forming positions of overlap (chiasmata)
    At these positions the non-sister chromatids break and exchange sections of genetic material
  • INDEPENDENT ASSORTMENT/ SEGREGATION
    Chromosomes are halved separating them making it completely random which chromosome from each pair ends up in which daughter cell at the end of meiosis
  • ORIENTATION OF CHROMOSOMES ON SPINDLE IN METAPHASE
52
Q

What is the meiotic cycle table?

A

S- DNA replicate so DNA content doubles
M1- by the end of M1 homologous chromosome separated into different cells
M2- by the end of M2 the DNA content is half of the original cell

53
Q

Compare mitosis and meiosis

A

MITOSIS:
- Produces cells with the same number of chromosomes as the parent cell (diploid)
- Genetically identical daughter cells
- Produces two daughter cells
- One division
- No pairing or separating of homologous chromosomes
- No independent segregation or crossing over of chromosomes
MEIOSIS:
- Produces cells with half the number of chromosomes as the parent cell (haploid)
- Genetically different daughter cells
- Producers four daughter cells
- Two divisions
- There is pairing and separating of homologous chromosomes
- There is Independence segregation and crossing over of chromosome

54
Q

What are the types of adaptations?

A
  • physiological- to do with chemical reactions of the body
  • behavioural- animal tendencies and behaviour
  • anatomical- physical/ structural features
55
Q

What are the types of selection?

A

Natural selection may affect allele frequencies within populations in several different ways
The types of selection that operate within populations are:
- Stabilising Selection
- Directional Selection
For continuously varying characteristics, these selection methods modify their frequency distributions in different ways

56
Q

What is stabilising selection?

A

a selective force that favours the phenotypes closest to the mean value of a trait.
- Stabilising selection acts against the extremes within va range of phenotypic variation
- This type of selection leads to a reduction in the range of variation within the population without any change in the mode
- Stabilising selection operates in an unchanging environment to maintain
the best adapted
genotypes within the population

57
Q

What is directional selection?

A

a selective force favouring individuals with an extreme trait and selects against phenotypes at other extremes.
- Directional selection operates in changing environments and acts for or against extremes of phenotype within the variable population.
- This type of selection leads to a reduction in the range of variation within the population, together with a progressive shift in the mode

58
Q

taxonomy. phylogeny

What is classification and 2 examples?

A

the arrangement of organisms into groups of various sizes on the basis of shared features.
taxonomy- a form of classification that focuses on physical similarities between different species,for ease of naming and identification.
phylogeny- the classification of organisms by these evolutionary relationships, so that every group shares a common ancestor.

59
Q

What is taxonomy and the 8 groups?

A

Taxonomy – the science of classification (naming and organising into groups)
– 8 levels of groups – called taxa, each group is a taxon
–Arranged as hierarchy (organised into levels)
–No overlap in levels
–3 Domains – Eukaryota, Bacteria & Archaea
–As you move down the hierarchy there are more groups but fewer organisms in each group
–Ends in species – group of similar organisms that reproduce to give fertile offspring

DOMAIN, KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES

60
Q

What is Binomial nomenclature?

A

Binomial nomenclature – naming system used for classification (all organisms are give one internationally acepted name in Latin
Genus species (genus with capital and all underlined or in italics)

61
Q

What’s the difference between artificial and phylogenetic classification?

A

artificial classification- classes organisms based on analogous characteristics where they have the same function we’re not the same evolutionary origins.
phylogenetic classification- Classifies groups based on shared features derived from their ancestors and arranges the groups into a hierarchy with no overlap

62
Q

What is courtship behaviour?

A
  • pre-matics activities for stimulation, partner attraction and mating institution
  • acts carried out by organisms to attract a mate of the right species of the opposite sex
  • species specific (only members of the same species recognise each other, preventing inbreeding and causing more successful fertile offspring)
63
Q

Why is courtship behaviour used by animals?

A
  • females are often only receptive to mating for a short amount of time
  • this is when their eggs are ready for fertelisation
  • if females respond favourably to courtship, offspring are likely to be produced
64
Q

What are pattern of courtship functions?

A
  • for species recognition
  • identification of a mate capable of breeding
  • to form a pair bond
  • insures stimulation and synchronisation of mating
65
Q

What is the criteria for successful courtship?

A
  • recognises members of their own species to ensure mating only occurs between the same species as only members of the same species to produce fertile offspring
  • identify a mate capable of breeding as both partners need to be sexually mature, fertile and receptive to mating
  • form a pair bond that will lead to successful mating/ raising offspring
  • synchronise mating so it takes place when there’s maximum probability of the sperm and egg mating
  • become able to breed by bringing a member of the opposite sex into a physiological state allowing breeding to occur
66
Q

How is courtship behaviour used in classification?

A
  • the more closely related the species, the more similar their courtship behaviour
  • same species have the same courtship behaviour

based on order and sequence of elements and moves

67
Q

What are some examples of courtship behaviour?

fireflies, crickets, peacocks, butterflies

A
  • FIREFLIES- give off pulses of light. The pattern of flashes is specific to each species.
  • CRICKETS- make sounds similar to morse code (the code is different for each species)
  • MALE PEACOCKS- show off their colourful tails, tail pattern only found in peacocks
  • MALE BUTTERFLIES- uses chemicals to attract females. only those of the correct species would respond.
68
Q

What is biodiversity?

A

the number and variety of living organisms in an area

69
Q

What is a habitat, species, population or community?

A

habitat- a place where organisms live
species- a group of similar organisms that are able to breed with each other and have fertile offspring.
population- a group of organisms from the same species in a habitat
community- all of the populations of the different species living in the same habaitat

70
Q

What are the components of biodiversity?

A
  • species diversity- the no. of different species and individuals in a community
  • genetic diversity- the variety of genes in a population of a species
  • ecosystem diversity- the whole range of different habitats on all scales
71
Q

How do you measure species diversity?

A

species richness (the no. of different species in a particular area at a time)

72
Q

How do you calculate the index of diversity?

A

d= N(N-1)/ ∈n(n-1)

N- total no. of organisms of all species
d- index of diversity
n- sum of no. of organisms of each species

73
Q

What does the index of diversity show?

A
  • the higher the value, the greater the species diversity
  • calculating index of diversity is quantitative as it provides a no. that makes it easier to compare the variety in different habitats
74
Q

What is the importance of species diversity?

A
  • The species diversity can be used as a measure of health of an ecosystem
  • The higher the species diversity index the more stable and ecosystem is likely to be
    Why?:
    The more different species there are, the more likely some species will be able to tolerate a change in the environment
75
Q

What is the impact of agriculture on biodiversity?

A
  • Agriculture reduces species diversity
  • Natural ecosystems usually develop into complex communities with lots of different species
  • Ecosystems associated with agriculture are controlled by humans and are reduced to a few species
76
Q

How do Harmful Farming Practices directly reduce species diversity?

A
  • Removing hedgerows
  • Overgrazing
  • Creating monocultures (replacing natural meadows with cereal crops)
  • Filling in ponds, draining wetland and marsh
77
Q

How do Harmful Farming Practices indirectly reduce species diversity?

A
  • Use of pesticides & inorganic fertilisers
  • Effluent runoff of slurry (animal waste) into water
  • Not rotating crops/ lack of intercropping / growing two or more crops in the same space.
78
Q

What are the different management techniques in agriculture?

A
  • Maintain existing hedgerows at the most beneficial height and shape. An A-shape provides better habitats than a rectangular one.
  • Plant hedges rather than erect fences as field boundaries.
  • Maintain existing ponds and where possible create new ones.
  • Leave wet corners of fields rather than draining them.
  • Plant native trees on land with a low species diversity rather than in species-rich areas.
  • Reduce the use of pesticides - use biological control where possible or genetically modified organisms that are resistant to pests. make food slightly more * Use organic, rather than inorganic, fertilisers.
  • Use crop rotation that includes a nitrogen-fixing crop, rather than fertilisers, to improve soil fertility.
  • Use intercropping rather than herbicides to control weeds and other pests.
  • Create natural meadows and use hay rather than grasses for silage.
  • Leave the cutting of verges and field edges until after flowering and when seeds have dispersed.
  • Introduce conservation headlands - areas at the edges of fields where pesticides are used restrictively so that wild flowers and is recognised that insects can breed.
79
Q

How do the management techniques help in diversity?

A
  • these practices will make food slightly more expensive to produce,
  • to encourage farmers there are a number of financial incentives from the Department for Environment, Food and Rural Affairs (DEFRA) and the European Union.
  • maintaining biodiversity is very important.
  • if biodiversity is reduced the global living system becomes increasingly unstable and we all rely on the global system for food and other resources.
80
Q

How does observing characteristics of species help to discover their genetic diversity?

A
  • Traditionally, genetic diversity was measured by observing the characteristics of organisms.
  • This method is based on the fact that each observable characteristic is determined by a gene or genes (with environmental influences).
  • The variety within a characteristic depends on the number and variety of alleles of that gene (plus environmental influences).
81
Q

Why does using observable characteristics to examine genetic diversity have its limitations?

A
  • A large number of observable characteristics are coded for by more than one gene.
  • They are polygenic, meaning they are not discrete from one another but rather vary continuously. It is often difficult to distinguish one from another.
  • Characteristics can also be modified by the environment. Differences may therefore be the result of different environmental conditions rather than different alleles.
82
Q

What’s gene sequencing?

A
  • Gene sequencing (or DNA sequencing) is the process of determining the exact order of nucleotide bases present in a gene, from a sample of DNA.
  • In these computerised systems, each nucleotide base can be tagged with a different coloured fluorescent dye -adenine (green), thymine (red), cytosine (blue) and guanine (yellow).
83
Q

How can a DNA sequence measure genetic diversity?

A
  • We can measure the genetic diversity of a species by sampling of DNA sequence. Each coloured band the DNA of its members and sequencing it to produce a pattern of represents one of the four nucleotide bases.
  • Analysis of these patterns allows us to compare one species with another or one individual with another of the same species to determine how diverse they are.
84
Q

How do mutations affect DNA sequences and genetic diversity?

A
  • Mutations that occur during DNA replication alter the sequence of bases present in a gene - over time these differences accumulate.
  • As a result, we would expect species that are more closely related to show more similarity in their DNA base sequences than species that are more distantly related.
85
Q

How does comparing mRNA base sequences show genetic diversity?

A
  • The base sequences on mRNA are complementary to those of the strand of DNA from which they were made.
  • It follows that we can measure DNA diversity, and therefore genetic diversity, by comparing the base sequence of mRNA.
86
Q

How can comparing amino acid sequences in proteins show genetic diversity?

A
  • The degree of similarity in the amino acid sequence of the same protein in two species will also reflect how closely related the two species are.
  • This can be done by counting either the number of similarities or the number of differences in each sequence.
87
Q

How can comparing immunological techniques. in proteins show genetic diversity?

A
  • The proteins of different species can also be compared using immunological techniques.
  • The principle behind this method is the fact that antibodies of one species will respond to specific antigens on proteins, such as albumin, in the blood serum of another.
  • The response is the formation of a precipitate.
  • The greater the number of similar antigens, the more precipitate is formed and the more closely the species are related.
  • The fewer the number of similar antigens, the less precipitate is formed and the more distantly the species are related
88
Q

What is DNA fingerprinting?

A

Analysing individuals DNA base sequences to see what genes or specific alleles are involved.

89
Q

What does STR stand for and how can this be used to look
for similarities and differences between two unknown individuals?

A

Short Tandem Repeats.
The DNA profile will produce coloured bands/ lines and these will be compared to see the similarities and differences between them.

90
Q

What in interspecific and intraspecific variation?

A

Interspecific Variation: Variation between different species/ one species differs from another.
Intraspecific Variation: Variation between members of the same species.

91
Q

What can cause intraspecific variation?

A
  • May be caused by genetic or environmental factors.
  • Genetic – all members of the same species have the same genes, but have different forms of these genes (alleles).
  • Different alleles cause variations in the organism’s phenotype.
  • Mutations may result in the change or loss of a protein.
92
Q

What is sampling?

A
  • To investigate variation, biologists cannot make reliable conclusions by taking a single measurement.
  • Sampling involved taking a selection of individuals from the target population (the population being investigated)
  • These individuals will represent the population as a whole (in theory)
93
Q

Why might sampling not be representative?

A
  • Sampling Bias – The selection process may be biased. The investigators may be making unrepresentative choices, either deliberately or unwittingly.
  • Chance – Even if sampling bias is avoided, the individuals chosen, by pure chance, may not be representative.
94
Q

How do you make sampling representative?

A

Random sampling: aims to prevent bias and eliminate
human involvement in choosing samples…
- Divide the area of study into a grid.
- Use a random number generator to choose coordinates.
- Take samples from intersection ( where they cross over)
of coordinates.

95
Q

How to minimise the
effect of chance when sampling?

A
  • Use a large sample size. More individuals selected, the smaller the probability that chance will influence the result/the less effect anomalies will have. Makes the data more reliable.
  • Use of statistical tests to analyse the data, determining the extent to which chance may have influenced the data.
96
Q

What is descriptive vs inferential statistics?

A

descriptive- to measure spread data (e.g. range, standard deviation, standard error)
inferential- allow us to use what we know to make inferences, used to test theory/ hypothesis

97
Q

What does standard deviation show?

A
  • A “thin” curve means that most values remain close to the
    average, and the standard deviation is small.

A “fat” curve means that there is a wider spread of values
about the mean, and the standard deviation is large.

98
Q

What is Chi-squared test?

A
  • to do with frequencies/ counts og things in categories
  • looks at significance of difference between expected and observed frequencies (w/ numerical value)
  • if no. small, small difference, accept null hypothesis (and vice versa)
99
Q

What is spearman’s rank test?

A
  • correlation to access degree of association (different measurements in the same sample)
  • looking for positive vs negative correlation between 2 variables
  • stats used to identify if correlation really exists (closer to 1/-1, more likely the correlatin
  • need to calculate critical value first
  • represents borderline between accepting and rejecting null hypothesis
100
Q

What is student’s t-test?

A
  • looking for the difference beteen 2 means
  • know if differece is significant or not
  • before you interpret results, work out critical value
  • represents borderline between accepting/ rejecting null hypothesis

a-level bio (aqa) (8 decks)

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