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Blueprint of life
1. Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allow change over many generations
Theory of evolution
• http://ed.ted.com/lessons/myths-and-misconceptions-about-evolution-alex-gendler
• Evolution: change in populations of living organisms over a long period of time
Theory of evolution
• Natural selection: the mechanism of evolution where organisms with traits suited to the environment will have the opportunity to pass on the traits to their offspring
• Inheritance: the transmission of genes for favourable traits from parents to offspring
• Evolution as a theory– Proposed by Charles Darwin and Alfred Wallace– Alternate theory by Jean Baptiste Lamarck
• outline the impact on the evolution of plants and animals of:– changes in physical conditions in the
environment– changes in chemical conditions in the
environment– competition for resources
Physical conditions
• E.g. temperature, availability of water, light, wind, slope and tides
• Urey and Miller’s experiments showed that organic molecules could form from inorganic molecules in the presence of UV radiation, lightning and high temperatures
Physical conditions
• Formation of ozone reduced UV radiation movement of organisms from water to land
• Change in Australian climate from cool and wet to hot and dry affected change of vegetation from rainforests to dry sclerophyll forests
Physical conditions
• Dust cloud produced by meteorite hitting earth changed the amount of light reduced vegetation extinction of dinosaurs
Chemical conditions
• E.g. the presence (or absence) of gases such as O2 and CO2, pH and concentrations of chemicals such as salts and heavy metals
• Early life forms (anoxic environment) produced CO2photosynthetic organisms production of oxygen aerobic organisms larger organisms
Competition for resources
• Changes in environmental conditions can lead to limited resourcesintroduction of a selective pressure
• environmental change• competition• predation• disease
competition of resources
• plan, choose equipment or resources and perform a first-hand investigation to model natural selection
• analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in a species
Task1. Identify the plant or animal species.2. Describe the change that occurred within the species.3. Include an illustration or photograph of the plant or
animal (remember to acknowledge your source).4. Describe the change in environment that occurred.5. Identify whether the environmental change was a
physical or chemical change.6. Identify and describe the selective pressures acting on
the organism as a result of the environmental change.7. Explain how (4) led to (2) (show cause and effect).8. Discuss whether you consider the example to be a
form of macro-evolution or micro-evolution.
• explain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution
Darwin-Wallace theory of evolution by natural selection
• All organisms arose from a common ancestor• Populations moved into new habitats and
adapted to their new environments • Natural selection requires:
– Variation in a species– Heritability of traits– Over-reproduction
• Speciation in isolation - a new species may occur when a population becomes isolated from the original group
Divergent evolution
• Recent divergence from common ancestor into different environments to evolve different traits
• “Adaptive radiation”• E.g. Darwin’s finches: Darwin observed 13
species of finches on the Galapagos islands which, he proposed, originated from one original population
Convergent evolution
• Similarities between distantly related species are due to similarities in environment (and selective pressures)
• E.g. Fin and flipper structures in sharks (fish), dolphins, whales and seals (mammals) and penguins (birds)
• describe, using specific examples, how the theory of evolution is supported by the following areas of study:– palaeontology, including fossils that have been
considered as transitional forms– biogeography– comparative embryology– comparative anatomy– biochemistry
1. Palaeontology
• Fossil remains: – Mineralised remains– Remains preserved in ice, amber, rock, ash, tar
• What would we expect to see?
1. Palaeontology
• Evidence:– Fossils around the world show a similar sequence
through which life developed– Transitional forms which have features common to
two groups of organisms• E.g. lobe-finned fish (Crossopterygii): fish
amphibians – Coelacanth https://www.youtube.com/watch?v=4jl_txxYQEA– Lungfish http://www.animalplanet.com/tv-
shows/other/videos/fooled-by-nature-lungfish/
1. Palaeontology
• E.g. Archaeopteryx: reptiles birds
1. Palaeontology
• Limitations:– Incomplete evidence – mostly hard bodied
organisms have been fossilised– Transitional organisms only present some
evolutionary transitions– Limit of carbon dating to 50000 years
2. Biogeography
• Geographical distribution of extant and extinct organisms
• Evidence:– New species are more similar to those in the area
compared to those far away• E.g. Bird species of Indonesia
2. Biogeography
– Distribution of flightless birds • Suggest common ancestor on Gondwana, speciation
occurred after continent split• No flightless birds on the northern continents (Laurasia)
3. Comparative embryology
• Comparison of developmental stages of species
• Evidence:– Vertebrate embryos (fish, amphibians, birds,
reptiles and mammals) all have gill slits and tailscommon
ancestry
4. Comparative anatomy
• Using similarities and differences in the structure (anatomy) of living organisms to determine evolutionary relatedness
• Evidence:– Homologous structures
• Same basic structure with modifications/adaptations• e.g. the pentadactyl limbCommon ancestor and divergent evolution
4. Comparative anatomy
– Analogous structures• Similar function,
superficially similar structure
• E.g. wings of bird and grasshopperConvergent evolution
due to same selective pressure (environment)
• perform a first-hand investigation or gather information from secondary sources (including photographs/diagrams/models) to observe, analyse and compare the structure of a range of vertebrate forelimbs
5. Biochemistry
• The sequence of biological molecules (DNA, proteins) can be compared to determine evolutionary relationships
• Evidence types:– Amino acid sequencing
• Proteins present in a number of organisms can be compared
– E.g. humans and chimpanzees have the identical sequence of amino acids in their haemoglobin and so they are more closely related than humans and gibbons, which have three differences.
5. Biochemistry
– DNA-DNA hybridisation• DNA from different organisms can be mixed to see how
well they bind to each other• The stronger the binding, the more similar the DNA
sequences are more closely related
5. Biochemistry
– DNA sequencing• Sequences of homologous genes from different
organisms determined
• Advantages– Can be quantitative– Can be used in organisms where there are no
homologous structures
• use available evidence to analyse, using a named example, how advances in technology have changed scientific thinking about evolutionary relationships
• analyse information from secondary sources on the historical development of theories of evolution and use available evidence to assess social and political influences on these developments
2. Gregor Mendel’s experiments helped advance our knowledge of the inheritance of characteristics
• outline the experiments carried out by Gregor Mendel
Mendel’s experiments
• http://ed.ted.com/lessons/how-mendel-s-pea-plants-helped-us-understand-genetics-hortensia-jimenez-diaz
Mendel’s experiments
• Mendel experimented with pea plants and studied the inheritance of traits by breeding them
• Pea plants are easily grown and bred, and have a short life cycle
Mendel’s experiments
• Mendel studied one trait at a time1. Mendel spent 2 years establishing
pure breeding lines2. Pure breeding lines were crossed3. A blending of traits were expected4. However all offspring resembled
one parent5. Other traits didn’t appear until
later generations
• describe the aspects of the experimental techniques used by Mendel that led to his success
Experimental techniques
• Establish pure breeding lines– Mendel took 2 years to do this– Kept isolated to prevent cross pollination
• Ensure cross breeding– Manual pollination– Anthers from recipient plant were removed to
prevent self-pollination
Experimental techniques
Validity of experiments
• Well controlled experiments– Examined one variable (trait) at a time– Large sample sizes (reliable)– Replicate data
• Data were accurate– Reduced experimental error– Quantitative data
• Produced a mathematical model to make predictions that he could test
• describe outcomes of monohybrid crosses involving simple dominance using Mendel’s explanations
Experimental outcomes
• Monohybrid: an individual with contrasting factors for one trait
Experimental outcomes
• From his results Mendel proposed:1. Mendel’s first law of dominance and segregation2. Mendel’s second law of independent assortment
Experimental outcomes
1. Mendel’s first law of dominance and segregation
– Characteristics/traits are determined by a pair of factors (which we now know of as genes)
– Each gamete contains one factor (due to segregation)
– Offspring inherit one trait from each parent
Experimental outcomes
– When two hybrids breed, they will have offspring with a ratio of 3 dominant trait:1recessive trait
– Different forms of a trait (gene) are termed alleles• E.g. green pea allele or yellow pea allele for seed colour
– Dominant traits are indicated by a capital letter, recessive trait by a lower case letter
– Pure breeding individuals have 2 of the same alleles
• distinguish between the terms allele and gene, using examples
Alleles and genes
• Mendel’s units of heredity are now known as genes which are located on chromosomes
• Traits are partially determined by our genes• Each cell has two copies of each gene – one
from each parent• Variations of the same gene are termed alleles
of the gene
• distinguish between homozygous and heterozygous genotypes in monohybrid crosses
Homozygous and heterozygous
• Pure breeding = homozygous = identical alleles of a gene
• Hybrid = heterozygous = different alleles of a gene
• explain the relationship between dominant and recessive alleles and phenotype using examples
Dominant and recessive
• Genotype: genetic makeup, combination of alleles
• Phenotype: appearance• If an organism is heterozygous for a trait, only
one allele will be expressed dominant allele• The recessive allele is masked
• outline the reasons why the importance of Mendel’s work was not recognised until some time after it was published
Recognition of Mendel’s work
• Mendel first published his work in 1866• It wasn’t until 1900 that 3 other scientists
rediscovered his paper, confirmed his findings and realised its significance
• Why?– Mendel’s work was ahead of its time. Cells and
chromosomes, mitosis and meiosis were unknown.– He presented his work to relatively small audiences.– His work was unique and not understood.– Mendel did not have a well known reputation as a
scientist.
• perform an investigation to construct pedigrees or family trees, trace the inheritance of selected characteristics and discuss their current use
• solve problems involving monohybrid crosses using Punnett squares or other appropriate techniques
• process information from secondary sources to describe an example of hybridisation within a species and explain the purpose of this hybridisation
3. Chromosomal structure provides the key to inheritance
• outline the roles of Sutton and Boveri in identifying the importance of chromosomes
Theodor Boveri
• Cytologist (studied cells)• 1896-1904: experiments on sea urchin eggs
and observed the nucleus and chromosomes during meiosis and fertilisation
Theodor Boveri
• Findings:– Boveri showed that a sperm and egg each
contributed 50% of the chromosomes during fertilisation
– Normal egg + normal sperm offspring with characteristics of both parents
– Anucleate egg + sperm offspring resembled male parent but were smaller and abnormal
Theodor Boveri
• Conclusions:– 2 sets of chromosomes were needed for normal
development (one set from each parent)– Inheritance factors are carried on chromosomes– There are multiple hereditary factors per
chromosomeChromosome theory of inheritance
Walter Sutton
• Studied meiosis in grasshoppers• Findings:
– Chromosomes occur in pairs of same size and shape during meiosis
– Chromosome numbers are halved during meiosis– Fertilisation restores the full number of
chromosomes
Walter Sutton
• Conclusions:– Chromosomes were the carriers of heredity units
and behaved in the same manner as Mendel’s ‘factors of inheritance’
– Chromosomes arrange themselves independently along the middle of the cell just before it divides
– Chromosomes are units involved in inheritance
• describe the chemical nature of chromosomes and genes
Chromosomes and DNA
• Each species has a characteristic number of chromosomes
• Individuals have 2 sets of chromosomes, one from each parent
Chromosomes and DNA
• Chromosomes are compact coils of DNA which are wrapped around histone proteins
• DNA = deoxyribonucleic acid
• identify that DNA is a double-stranded molecule twisted into a helix with each strand comprised of a sugar-phosphate backbone and attached bases – adenine (A), thymine (T), cytosine (C) and guanine (G) –connected to a complementary strand by pairing the bases, A-T and G-C
DNA structure
• Watson and Crick discovered the structure of DNA to be a double helix
• DNA is composed of nucleotide monomers– Deoxyribose sugar– Phosphate– Nitrogenous base
• A: adenine• T: thymine• G: guanine• C: cytosine
DNA structure
• The nucleotides form two strands which are joined by complementary base pairing– A with T– G with C
• The DNA backbone are alternating sugar and phosphate molecules
Genes and chromosomes
• A gene is the smallest hereditary unit• Each gene is a portion of DNA with a specific
sequence• A chromosome is a linear sequence of genes
• explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes
Meiosis
• Chromosome behaviour during meiosis leads to increased genetic variation
• During meiosis I, two events contribute to genetic variation:1. Independent assortment of homologous
chromosomes2. Crossing over
Meiosis
1. Independent assortment of homologous chromosomes
– Homologous chromosomes line up at the equator during prophase I
– The paternal and maternal chromosomes sort randomly i.e. not all paternal chromosomes will segregate to the same pole
Meiosis
2. Crossing over– Aka chiasma event– As the homologous chromosomes pair up
along the equator, genetic material can be exchanged during metaphase I
Mixing of paternal and maternal genes Increases genetic variation
Meiosis
• Outcomes:– 4 haploid cells are created– The genes in the haploid cells are a new
combination of the parental genes– Crossing over allows maternal and paternal genes
to assort independently
• process information from secondary sources to construct a model that demonstrates meiosis and the processes of crossing over, segregation of chromosomes and the production of haploid gametes
• explain the role of gamete formation and sexual reproduction in variability of offspring
Variability
• Variability = the number of alleles in the gene pool
• Variation and variability are due to both genetics and the environment
• Variation and variability only confer an evolutionary advantageous if there is a genetic basis
Variability
1. Gamete formation– Crossing over and independent assortment and
segregation result in different combinations of alleles in gametes compared to parents
– The result is greater variability in gametes
2. Fertilisation– Random fertilisation of gametes increases
variation because of the different possible combinations variability in a population
• describe the inheritance of sex-linked genes, and alleles that exhibit co-dominance and explain why these do not produce simple Mendelian ratios
Non Mendelian inheritance
• Inheritance of traits do not show Mendelian ratios if:– Genes do not sort independently– Genes do not show dominance
• Two situations are:– Sex-linked inheritance– Codominance
Sex-linked inheritance
• Sex chromosomes:– XX - female– XY - male
Sex-linked inheritance
• Sex determination– During meiosis sex chromosomes segregate into
separate gametes – The father (through the sperm) determines the
sex of the offspring– The sex chromosomes carries genes responsible
for sexual characteristics e.g. Y carries the testis-determining gene
Sex-linked inheritance
Sex-linked inheritance
• The X chromosome can also carry genes for non sexual characteristics sex-linked genes
• Inherited along with sexual traits• Since males only have one X chromosome,
they only have one allele for each sex-linked trait
• describe the work of Morgan that led to the understanding of sex linkage
Thomas Hunt Morgan
• Experimented with the fruit fly, Drosophilamelanogaster
• Morgan performed crosses with normal fruit flies which have red eyes and also mutant males with white eyes
Thomas Hunt Morgan
• http://splash.abc.net.au/en_US/media/-/m/1479525/when-flies-inherit-white-eyes
Thomas Hunt Morgan
• Experiments:– Crossed a pure
breeding white eyed male with a pure breeding red eyed female
– Crossed hybrid offspring with each other
– All white eyed flies were males (F2 generation)
Thomas Hunt Morgan
• Experiments:– Test cross: white-
eyed male x hybrid red eyed female
• Both males and female offspring had white eyes
Thomas Hunt Morgan
• Conclusions:– The gene for eye colour in fruit flies is located on
the X chromosome– Hereditary factors can be exchanged between the
X chromosomes of an individual
• Morgan’s work provided evidence for sex-linkage (inheritance of traits linked to genes that determine gender)
Chromosome theory of inheritance
• The behaviour of pairs of alleles can be explained by the movement of chromosomes during meiosis (proposed by Sutton and Boveri)
• Pairs of alleles are carried on pairs of homologous chromosomes (proposed by Morgan)
• Mendel’s laws are explained by the separation and recombination of pairs of alleles (combination of Sutton, Boveri and Morgan’s work) if they are not sex-linked (Morgan) and they show dominance
• explain the relationship between homozygous and heterozygous genotypes and the resulting phenotypes in examples of co-dominance
Co-dominance
• Some genes do not show dominance of one over another
• In heterozygotes (hybrids), both alleles are expressed as unblended phenotypes
Co-dominance
• Example: cattle– Pure breeding (homozygous) cattle can have red
or white coats– Hybrids have a “roan” appearance
Co-dominance
• Example: Human blood types– Red blood cells have proteins on their surface
called “antigens”– Different antigen
systems for red blood cells:
• ABO• Rhesus (+ and -)
Co-dominance
• Inheritance of ABO blood types do not show Mendelian ratios
• solve problems involving codominance and sex linkage
• outline ways in which the environment may affect the expression of a gene in an individual
Environment and phenotype
• Variations in organisms are usually determined by a combination of their genes and the environment
• The environment can:– Mask gene expression– Enhance gene expression
Environment and phenotype
• Example: Siamese cat– Normally all white
• Dominant trait “W”
– A recessive mutation “w” causes pigment to be produced at the extremities
• Pigment is produced at cooler temperatures
• Older cats which have poor circulation will have more pigmentation
Environment and phenotype
• Example: hydrangeas– Colour of flower depends on pH of the soil– Acidic soil results in blue flowers– Alkaline soil results in pink flowers
Epigenetics
• http://learn.genetics.utah.edu/content/epigenetics/twins/
• identify data sources and perform a first-hand investigation to demonstrate the effect of environment on phenotype
4. The structure of DNA can be changed and such changes may be reflected in the phenotype of the affected organism
• describe the process of DNA replication and explain its significance
DNA replication
• Production of 2 identical double stranded DNA molecules from one original double helix
• This process is semi-conservative• Occurs before cell division to ensure each
daughter cell has a complete copy of the genetic material
DNA replication
1. DNA double helix unwinds– An enzyme called helicase unwinds the DNA
strands
DNA replication
2. DNA unzips– Complementary base pairs separate creating a
replication “fork”
DNA replication
3. Nucleotides are added by DNA polymerase– Existing DNA strands act as a template– Addition of nucleotides is in an antiparallel
direction– DNA pol.
also checks for errors in DNA sequence
DNA replication
DNA replication
• Significance– During mitosis genetic material must be passed on
from one cell to another for growth and repair so we need exact copies of the DNA
– During meiosis genetic material must be reproduced so that it can be passed onto the next generation
– Errors in replication will have an effect on the phenotype of the organism
• explain the relationship between proteins and polypeptides
Proteins and polypeptides
• Proteins consist of one or more chains of amino acids folded in a 3-dimensional structure
• Amino acids are joined in chains by peptide bonds to form polypeptides
• There are 20 different amino acids
• analyse information from secondary sources to outline the evidence that led to Beadle and Tatum’s ‘one gene – one protein’ hypothesis and to explain why this was altered to the ‘one gene – one polypeptide’ hypothesis
Beadle and Tatum
• 1 gene - 1 protein hypothesis• Beadle’s early experiments:
– Normal fruit flies exposed to X-rays – Offspring with
different eye colour– Hypothesis: offspring
had defective enzyme for eye pigment
Beadle and Tatum
• Experiments on Neurospora crassa (a mould)– Irradiated with X-rays to induce mutations– Some of the mutants could not produce an
essential amino acid defective enzyme
– Mutants crossed with normal mould and found some offspring with the defect genetic basis
• 1 gene - 1 enzyme hypothesis
• outline, using a simple model, the process by which DNA controls the production of polypeptides
Polypeptide synthesis
• Central dogma:
Polypeptide synthesis
• Chemicals involved:– DNA– RNA
• Single stranded• Sugar is ribose (not deoxyribose)• Uracil (U) instead of thymine (T)• 3 types:
– Messenger RNA (mRNA)– Transfer RNA (tRNA)– Ribosomal RNA (rRNA)
Polypeptide synthesis
• https://www.youtube.com/watch?v=h5mJbP23Buo
Polypeptide synthesis
1. Transcription (DNA RNA)– RNA polymerase binds to the DNA at a promoter
region (start of a gene) and unzips the DNA– Transcription occurs where the DNA is used as a
template for the synthesis of a complementary mRNA strand
2. mRNA moves out of the nucleus into the cytoplasm and binds to a ribosome (made of rRNA)
Polypeptide synthesis
3. Translation (RNA protein)– Ribosomes move along the mRNA attaching
tRNA to complementary base pairs on the mRNA• Each tRNA has 3 unpaired bases (“anticodons”) which
recognise 3 base pairs on the mRNA sequence (“codon”)
• Each tRNA is also attached to an amino acid
– The tRNA adds an amino acid to the growing polypeptide chain
Polypeptide synthesis
4. The amino acid detaches from the tRNAwhich moves into the cytoplasm to pick up another amino acid
5. When the polypeptide chain is complete, it can be joined by one or more polypeptides which are then folded into a protein
6. The mRNA is broken down into nucleotides
One gene – one ???
• Genes are now known to encode enzymes, one or more polypeptides, mRNA, tRNA…
• … and so a gene is a sequence of nucleotides that codes for any molecular cell product
• perform a first-hand investigation or process information from secondary sources to develop a simple model for polypeptide synthesis
Protein synthesis model
• Your model can be:– Video– Role play– Animation– 3D model
Protein synthesis
• http://highered.mheducation.com/olc/dl/120077/micro06.swf
• https://www.youtube.com/watch?v=u9dhO0iCLww
• discuss evidence for the mutagenic nature of radiation
Mutations
• Are changes in the sequence of DNA• Mutations can be characterised by:
1. The amount of genetic material changed• A single base pair or whole sections of chromosomes
2. Effect of mutation on phenotype• Harmful, beneficial or neutral• Somatic (affects individual) or gametic (affects
offspring)3. Origin of mutation
• Spontaneous (errors in replication) or induced (by mutagen)
Mutagens
• Environmental factors which cause mutations– Chemical mutagens
• Tobacco smoke, asbestos, preservatives
– Biological mutagens• Viruses and micro-organisms
– Mutagenic radiation• Ionising radiation
Evidence for mutagenic radiation
• During late 1800s and early 1900s, effects of radiation were unknown
• Scientists working on radioactivity developed various illnesses– E.g. Marie Curie developed leukaemia due to
overexposure to radiation (from radium)
Evidence for mutagenic radiation
• Survivors of the atomic bomb in Hiroshima suffered from physical mutations
• Victims of Chernobyl nuclear reactor meltdown suffer from infertility and genetic mutationsstrong link between exposure to ionising radiation and illnesses such as leukaemia and other cancers
• explain how mutations in DNA may lead to the generation of new alleles
Mutations and new alleles
• Mutations can change the sequence of nucleotides in DNAChange in gene(s)Creation of new variation of the gene (allele)
• E.g. A mutation in the haemoglobin gene causes sickle cell anaemia
Mutations and new alleles
• Mutation types:– Point mutations – single base pair substitution– Frame-shift mutation – bases are added or
deleted– Duplication of sequences
• process information to construct a flow chart that shows that changes in DNA sequences can result in changes in cell activity
• explain how an understanding of the source of variation in organisms has provided support for Darwin’s theory of evolution by natural selection
Support for evolution
• Understanding the genetic basis of mutation and inheritance provides a mechanism to explain Darwin’s theory of evolution
Support for evolution
• Evolution requires:– Variation in the population
• Mutations in DNA new alleles genetic diversity
– Selective pressure and survival of favourable traits– Favourable traits are passed on to offspring
• Germline mutations are heritable and passed onto offspring
• describe the concept of punctuated equilibrium in evolution and how it differs from the gradual process proposed by Darwin
Punctuated equilibrium
• Covered in earlier slide
• process and analyse information from secondary sources to explain a modern example of ‘natural’ selection
• process information from secondary sources to describe and analyse the relative importance of the work of:– James Watson– Francis Crick– Rosalind Franklin– Maurice Wilkins
in determining the structure of DNA and the impact of the quality of collaboration and communication on their scientific research
5. Current reproductive technologies and genetic engineering have the potential to alter the path of evolution
• identify how the following current reproductive techniques may alter the genetic composition of a population:– artificial insemination– artificial pollination– cloning
Reproductive technologies
• Technology used to improve reproduction– Selective breeding or artificial selection– Hybridisation – Artificial insemination– In vitro fertilisation – Cloning
Reproductive technologies
• Artificial pollination– Aka selective breeding– Dates back to 870 BC– Used by Mendel in his pea
experiments
Reproductive technologies
– Involves removing the stamens of a flower and dusting the pollen onto the stigma of the same flower (self-pollination) or another flower (cross-pollination)
Reproductive technologies
• Selective breeding– Mating a male with one desirable characteristic
with a female with another desirable characteristic offspring with both characteristics
Reproductive technologies
– E.g. Friesian (large quantities of milk) x with a Jersey cow (creamy milk) offspring which produce large amounts of creamy milk
– Disadvantages:• Breeding of undesirable traits (E.g. udders that are so
large that cows have difficulty walking)• High monetary and time costs
Reproductive technologies
• Artificial insemination– Taking sperm from a chosen male and artificially
introducing it into several selected females– Advantages:
• Overcomes problem of transporting animals, only frozen sperm needs to be transported
• More cost effective• Safer for animals• Many females can be inseminated• Semen can be frozen indefinitely • Used for conservation
Reproductive technologies
• In vitro fertilisation (IVF)– Fertilisation occurs outside the mother’s body.
Zygotes are grown to a certain stage before implanting into the mother or frozen.
– Used when parents have decreased fertility
Altering genetic composition of population
• Particular traits are selected for by the breeder
• New combinations of alleles arise which are then selected for and become the dominant alleles in the population
• Genes for infertility are now passed on, the opposite of natural selection
• Sperm banks may result in selection of traits• Long term decrease in genetic diversity
Cloning
• To make a copy:1. Reproductive cloning: creating an identical
whole organism (asexual reproduction)
2. Therapeutic cloning: producing an early embryo as a source of stem cells
3. Gene cloning: producing a copy of a gene for genetic engineering
• process information from secondary sources to describe a methodology used in cloning
Somatic cell nuclear transfer
• http://ed.ted.com/featured/MViO4vvy
• outline the processes used to produce transgenic species and include examples of this process and reasons for its use
Transgenic organisms
• A transgenic organism is an organism in which a gene from another species has been introduced by genetic engineering
Producing a transgenic species
1. ‘cut’: a gene for a favourable characteristic is removed from the cell of an organism, using restriction enzymes
2. ‘copy’: multiple copies are made (called ‘gene cloning’)—this step is usually carried out in bacteria
Producing a transgenic species
3. ‘paste’: the genes are inserted (injected) into an egg cell of another species and after fertilisation become part of the newly formed organism’s DNA
4. The egg develops into a mature organism (a transgenic species) with the new gene
Producing a transgenic species
• In step 3, genes can be introduced in a number of ways:i. Microinjection of
DNA into egg cellsii. Biolistics or gene gun
Producing a transgenic species
iii. Electroporation uses an electric current to open up cells
iv. Transduction by a viral vector
GFP markers
• Green fluorescent protein markers are used to indicate successful gene integration
Example: Transgenic cotton
• Aka “Bt” cotton, as it contains a gene from Bacillus thuringiensis
• Collaboration between CSIRO and Monsanto
Example: Transgenic cotton
• Problem: Traditional pesticides used on cotton plants were becoming ineffective from pests such as the caterpillar of the Helicoverpa zeamoth Resistance to pesticide
Example: Transgenic cotton
• Bt cotton plants were genetically modified to contain a gene that codes for a protein that kills the caterpillar
• The gene originally came from the bacterium Bacillus thuringiensis
Example: Transgenic cotton
• Farmers don’t need to spray as much pesticides and only need to use narrow spectrum pesticides
• The protein produced from the Bt gene is a toxin which only affects caterpillars and are safe for humans and most insects
Example: Transgenic cotton
• Steps:1. Cotton seedlings are cut into small pieces and
grown in medium to develop into embryos2. The Bt gene is cut from the genome and
multiplied3. Another bacterium, Agrobacterium tumefaciens,
is used to transfer the Bt gene into the cotton embryos
4. the recombinant embryos then develop into full plants which carry the Bt gene
Uses of transgenic organisms
• It can also be used to:– create genetically modified (GM) foods which
have higher nutrients and yields (Golden rice)– create disease and pest resistant crops– treat disease (gene therapy)
• discuss the potential impact of the use of reproduction technologies on the genetic diversity of species using a named plant and animal example that have been genetically altered
Impact of genetic modification on diversity
• In the short term, creating transgenic species increases genetic diversity
• However, in the long term, it may decrease genetic diversity since the original genetic material of some organisms may be reduced or lost forever
• analyse information from secondary sources to identify examples of the use of transgenic species and use available evidence to debate the ethical issues arising from the development and use of transgenic species
