Blueprint of Life Flashcards
Macro evolution
Millions of years, arising new species.
E.g wolf and dog from common ancestor
Micro evolution
Shorter time periods, pop changes but no new species. E.g. Different dog breeds
Outline the impact on the evolution of plants and animals of
Changes in physical conditions in environment
Early organisms; water to land habitat→ reduced UV radiation (ozone forming)
Aus climate; cool/wet→ hot/dry, rain forests to woodland,
Lakes dry up→ evolution to conserve water
Ice age→ change in sea levels, temp. Dinosaurs→ meteorite; reduced light, plant life→ no food
Outline the impact on the evolution of plants and animals of
Changes in chemical conditions in environment
First life; anoxic environment; some produced CO2; led to photosynthetic organisms
Increased oxygen levels; evolution of organisms using oxygen (complex-diverse animals today)
E.g. Peppered moth; industrial revolution. Black moth protected from soot; white stand out and killed
Outline the impact on the evolution of plants and animals of
Competition for resources
Comp for light, soil, nutrients, water, shelter, mates, territory
Organisms compete; most successful survive and reproduce; pass on genes
Plan, choose equipment or resources and perform a first-hand investigation to model natural selection
Pop begins with 30 moths (10 black, grey, white) → chart works out offspring colours.
Spin for predator (colour removed) shuffle cards; repeat until trend recognisable; dominant species?
Analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in species (SNOW GUM)
HIGH ALTITUDE Cold, shallow soil, exposed to snow Small and twisted to bend away from elements. Short leaves, Large fruit, Thin bark More resistance to frost, Short trees
LOW ALTITUDE Warm, high precipitation, Tall and straight to receive nutrients and rainfall Long leaves, Small fruit, Thick bark Less resistance to frost, Tall trees
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
PALAEONTOLOGY
Scientific study of fossils and extinct life
Fossils→ evidence of past life forms; evolutionary transitions to modern living forms
Undisturbed rock fossils; show sequence living things arose; have common features (change over time)
E.g. Lobe- finned fish; bones in fin→ dragging from water to land (amphibians evolved from fish)
Limitations; fossil record incomplete, bias to fossils with body/environment better suited to fossilisatio
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
BIOGEOGRAPHY
Study of geographical distribution of organisms
Darwin/Wallace theory; new species; group isolated from rest→ thought species close; similar, far apart; different
E.g. Flightless birds/continental drift→ common Gondwana ancestor; different pop evolved on continents. E.g. Emu in Aus, Kiwi in NZ→ share similar features; flat breastbone
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
COMPARATIVE EMBRYOLOGY
Comparison of similarities in vertebrate early embryos
Embryos of closely related organisms have homologous parts→ support common ancestor
E.g. Fish, bird, mammal, reptile embryos; gill slits, tails (later internal gills in fish)
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
COMPARATIVE ANATOMY
Similarities in organisms structure (similarities; common ancestor, differences; modification) evolution
Limitations; fossils often incomplete→ hard to compare with extinct life form
E.g. Pentadactyl limb; (homologous structure) same basic sequence of bones in dog, human, bird;
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
BIOCHEMISTRY
DNA hybridisation:
Compare DNA sequence of 2 organisms; unzip, zip codes to match
E.g. Heat applied to chimpanzee, human DNA→ high temp means more closely related; 83℃
Amino acid sequencing
Similarities in protein sequencing→ Similarities; shared ancestor. Differences; evolved over time
E.g. Humans. chimps→ identical sequence in haemoglobin. More related than gibbons,humans (3 diff
Use available evidence to analyse using a named example, how advances in technology have changed scientific thinking about evolutionary relationships (CLASSIFICATION OF PRIMATES CHANGED)
DNA in amino acid sequencing, DNA hybridisation→ new biochemical evidence
Historically; orangutans, gorillas, chimps→ 1 family, humans another (based on structure of leg, teeth)
60’s→ Chimps, humans→ identical haemoglobin, cytochrome c sequence→ different to gorilla
Humans, chimps small DNA difference, (more closely related than orangutans→ diverged earlier)
New genetic tree→ humans, chimps diverged more recently from common ancestor
Explain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution
Proposed; variations within species and more offspring produced than can survive and reproduce
Some individuals have adaptive characteristics; enable survival better→ passed on to next generation
Over time; natural selection→ pop with adaptations most suited to environment
Source of variation; gene mutation; phenotypic advantage
Isolation; if species pop geographically isolated, interbreeding stops; separate species develop
Divergent; one species forms other with adaptations suited to variety of environments
E.g. Aus marsupials; evolved from common possum like ancestor; common structure, but dominant differences
Convergent; Organisms come to resemble each other; share similar environment, perform same function. E.g. Streamline dolphin/shark body for swimming in sea. Similar but dolphin; mammal, shark; fish
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
England 1858→ Darwin/Wallace published theory
Invention of machinery, people flocked to cities (disease) social changes in class, French revolution
New discoveries; people looked to science.
Outline the experiments carried out by Gregor Mendel
Heredity in garden peas; pure bred (consistent characteristics)
Deliberately crossed one variety with another→ observed next generation
Removed stamens (so no self pollination) repeated experiments, kept records
Monohybrid cross; Offspring of cross (F1) Crossbred tall x short (all offspring tall) Tall then grew (F2) F2 most tall, some short (3:1)
Law of segregation; 2 genes that control each characteristic; segregate during reproduction; 1 factor each in a gamete→ factors recombine at fertilisation (match together)
Law of Independent assortment; Pairs segregate independently of other pairs of factors
Reproductive cells combine at fertilisation; offspring had one factor for tallness and one for shortness→ only tallness observed (dominated shortness)
Describe the aspects of the experimental techniques used by Mendel that led to his success
Cross pollinated by hand, studied large number of characteristics
Used quantitative data, studied characteristics one at a time
By chance→ characteristics he studied carried out on different chromosome
Studied separately characterises occurring in pairs (tall or short) previously; whole plant studied
Solve problems involving monohybrid crosses using Punnett squares or other appropriate techniques
Check for dominance and assign symbols
Write down parents phenotype and genotype
Write down parents gametes gametes, noting only one allele for characteristic in gamete
Make punnett square and write down all possible crosses underneath
Describe outcomes of monohybrid crosses involving simple dominance using Mendel’s explanations
2 different parents→ F1 generation only has dominant trait
F1 crossed→ F2 generation has dominant trait, recessive trait in (3:1)
Process information from secondary sources to describe an example of hybridisation within a species and explain the purpose of this hybridisation
Hybridisation; Crossbreeding two genetically non-identical individuals
Parents with desirable traits selected; offspring reflecting desired traits further breed; hybrid offspring
E.g. Hybridisation within species: Labradoodle (Labrador x Poodle) → successful hybridisation leads to hybrid vigour (increased strength, better health, greater fertility)
ADVANTAGES OF HYBRIDISATION
Increases genetic variety
Combine best features of each parent→ hybrid vigour
DISADVANTAGES OF HYBRIDISATION
May combine weaker features of parents→ offspring have less stamina, resistance to disease etc
Very expensive (especially if no hybrid vigour)
Sometimes offspring are infertile or reduced fertility
Distinguish between homozygous and heterozygous genotypes in monohybrid crosses
Homozygous→ Identical alleles of a particular gene for a characteristic.
E.g. TT, tt, HH, hh
Heterozygous→ Two different alleles of a particular gene for a characteristic.
E.g. Aa, Bb, Ee
Distinguish between the terms allele and gene, using examples
Gene→ Smallest unit of hereditary. Codes for a particular characteristic
E.g. Eye colour gene
Allele→ Variations of a gene
E.g. Brown, blue, green, black eye colour
Explain the relationships between dominant and recessive alleles and genotype using examples
Dominant alleles→ Form of gene expressed in heterozygous condition, masking the other (recessive) form of same gene. Written in UPPERCASE letters.
E.g. T
Recessive alleles→ Form of gene expressed in homozygous condition. Written in lowercase letters.
E.g. t
Outline the reasons why the importance of Mendel’s work was not recognised until some time after it was published.
Paper only presented to small group; work suddenly appeared (may not have been noticed)
Work radically different to previous; may not have been understood and little known about cels
He wasn’t recognised scientist; more likely to have been noticed if was serious scientist
BOVERI (1896-1904)
Sea urchin egg experiment→ behaviour of cell nucleus and chromosomes (in meiosis and fertilisation)
Already known→ organisms has set number of chromosomes and in fertilisation (egg and sperm fuse)
Found nucleus of egg and sperm contribute 50% of chromosomes to zygote
Experiments:
Egg and sperm fuse; resulting offspring have characteristics of parents. If only one parent nucleus; abnormalities→ showed that complete set of chromosomes needed for normal; inheritance factors on chromosomes in nucleus
SUTTON (1877-1916)
Meiosis of grasshopper cells→ observed chromosomes occur in visible pairs in meiosis (paternal and maternal)
During meiosis; chromosome number is halved, chromosome in each pair separate; gamete receives one chromosome from each pair→ fertilisation resotes full number in zygote
Concluded that:
Chromosomes carriers of hereditary units;arrange themselves independently in middle of cell before divides
Chromosomes units involved in inheritance; believed that several Mendelian factors present in one chromosomes; therefore inherited as unit
Before and after Sutton and Boveri
Before→ Hereditary factors found in nucleus and cytoplasm; After→ Nucleus only
Before→ Proteins store hereditary info. After→ full set of paired chromosomes
Before→ gametes transport factors to pass onto next generation. After→ random assortment during meiosis
Before→ Chromosomes believed to disappear and reappear. After→ Occur in set numbers, in pairs
Describe the chemical nature of chromosomes and genes
Chromosome→ made of DNA, proteins
Proteins→ histone proteins bind to DNA to form chromatin (in nucleus)
DNA→ Double helix structure, basic building block of nucleotide (base, sugar, phosphate)
4 bases; Adenine (A) and Thymine (T), Cytosine (C ) and Guanine (G)
NUCLEOTIDE
2 nucleotides linked by covalent bonds between sugar and phosphate
DNA tightly wrapped around histone→ protect from damage, allow long DNA length to be packaged so it doesn’t move around cell in cell division
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 contains info in specific sequence of nucleotides (sugar, phosphate, base)
Spiral double helix (rungs of ladder→ hydrogen bonds linking (A,T) and (C,G)
Identify data sources and perform a first hand investigation to demonstrate the effect of environment on phenotype
Radishes grown in 2 petri dishes; one kept in light. Other kept in dark
In dark: grew taller faster; but had yellow leaves → In light: shorter height
Radishes in dark moved into light→ leaves became green; gene undamaged, but not expressed in dark
Explain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes
In meiosis; genetic variation from crossing over, random segregation, independent assortment
Meiosis; One cell (2 divisions) → 4 haploid cells (genes in each; new combo of parent genes)
Independent assortment; paternal and maternal chromosomes sort out independently of one another
Maternal don’t all move into one gamete and paternal into another→ random where it ends up→ mixes paternal and maternal (genetic variation)
Chromosomes in pair separate→ ensures chromosomes number in gametes is half of original
Explain the role of gamete formation and sexual reproduction in variability of offspring
Variability→ Different forms of a gene within a population (from genes, environment or both)
Sexual reproduction increases variability→ increasing gene recombination
Greater variability improves pop’s ability to adapt to changes in environment
Meiosis and fertilisation→ when gametes form, cross over, random segregation→ results in genetic recombination of paternal and maternal genes within each gamete
Describe the inheritance of sex-linked genes, and alleles that exhibit co-dominance and explain why these do not produce simple Mendelian ratios
Mendelian ratios→ only when similar conditions to
Mendel; if genes don’t assort independently,or show dependence→ Mendel’s ratios not obtained
Cells; 23 chromosome pairs (22 x autosomes, 1x sex chromosomes) Female genotype XX, Male; XY
Offspring;equal chance of male or female; determined during meiosis; transfer 1 sex chromosome to each gamete; fusion of gametes in fertilisation
Meiosis; Females (44 autosomes plus XX) → halved egg gets 22 autosomes and X. Males→ Half get 22 autosomes and X, half get 22 autosomes and Y
X from mother and father→ will be female (XX) X from mum, Y from dad→ will be male (XY)
Mendel’s experiments; no sex-specific effects; sex-linked inheritance is deviation from Mendel’s ratios
Describe the work of Morgan that led to to the understanding of sex linkage
At time; Unknown why number of traits that separate in meiosis exceeds number of chromosomes
Sutton/Boveri→ more than one trait is present on each chromosomes (didn’t demonstrate)
1910→ Morgan experiments on gene eye colour in fruit flies; located on X chromosome→ heredity factors exchanged between X chromosomes
Drosophila Melanogaster (normally red eyes, but found mutant white eyed male) → crossed to see if white eyed gene would show Mendel ratio
MORGAN’S CROSSES
CROSS 1
Pure bred parents o obtain F1 hybrid offspring
White eyed male and red eyed female
CROSS 2
Crossed F1 hybrid offspring to obtain F2 generation
Expecting Mendelian 3:1 ratio but more than 80% had red eyes and less than 20% white eyes
Most white eyed were male. Thought females couldn’t have white eyes
CROSS 3
Typical cross to investigate hypothesis → crossed white eyed male with heterozygous red eyed female
Results shown in F2 generation,both males and females had white eyes
Next (and correct) hypothesis→ white eyed characteristic is ‘sex-limited’. Genetic crosses proved red eyes were sex limited (carried on sex chromosome)
Explain the relationship between homozygous and heterozygous genotypes and the resulting phenotypes in examples of codominance
Doesn’t show Mendelian pattern (pairs of alleles don’t show dominance over the other)
Heterozygote where 2 different alleles for same gene; both expressed separate (both dominant)
E.g. Cattle have red or white→ Heterozygous may have red and white coat→ roan (not in patches but interspaced red and white hairs)
Outline ways in which the environment may affect the expression of a gene in an individual
Genotype + environment= phenotype
E.g. (TT)plant may end up same size as (tt), if grew in unfavourable conditions (lack of water)
E.g. Temp can affect phenotype of animals: or effect of soil pH on colour of hydrangea flowers;
Pink flowers in alkaline or blue flowers in acidic
Identical twin; differences due to environmental rather than genetics→ One may have freckles (sun exposure) other may not
Environmental factors influencing humans; smoking, physical activity levels, diet, nutrition
Describe the process of DNA replication and explain its significance
DNA replication→ DNA copied; produce new molecules with same base sequence
STAGE 1: DNA double helix unwound, separated into strands (hydrogen bonds broken)
STAGE 2: Strands act as templates→ Nucleotides and bases form bonds with bases on parent strand
STAGE 3: Daughter DNA molecules rewind in double helix; identical in base sequence to parent (due to complementary base pairing)
Each of new strands is complementary to template it was made on and identical to other template
Outline using a simple model, the process by which DNA controls the production of polypeptides
Polypeptide synthesis; uses RNA→ single stranded nucleic acid (bases A, C, G and Uracil→ replaces Thymine; T)
Three types of RNA: mRNA (messenger RNA) tRNA (Transfer RNA) and rRNA (ribosomal RNA)
DNA to polypeptide; DNA code determines amino acid sequencing in polypeptide chain→ DNA info transcribed to mRNA from template strand
3 nucleotides on mRNA→ codon for particular amino acid
Outline using a simple model, the process by which DNA controls the production of polypeptides
TRANSCRIPTION STAGE
Copy of gene is made (RNA not DNA) → carries info for making polypeptide (mRNA)
Double helix unwinds; RNA nucleotides assemble use one DNA strand as template; mRNA separates from DNA and double helix reforms
Outline using a simple model, the process by which DNA controls the production of polypeptides
TRANSLATION STAGE
Ribosomes move along mRNA molecule→ transfer RNA molecules present around ribosomes (bind to them→ only bind to anticodon that is complementary to codon on mRNA)
Codon and anticodon base link (form hydrogen bonds)
tRNA molecules carry amino acids→ bonded by peptide linking; dipeptide formed→ upper tRNA detaches, another one binds→ chain of 3 amino acids forms
These stages are repeated until a polypeptide is formed
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
1941→ mutants of fungus→ led to discovery of genes provide instructions for making proteins
Hypothesis; gene controls production of one enzyme→ evidence needed
Designed experiment to attempt to mutate genes of mould→ evidence led to hypotheses; genes affect enzyme productivity→ Breakthrough! (At time; ongoing debate; heredity material protein or DNA?)
EXPERIMENT:
Irradiated bread mould with X-rays (induce mutations) → showed some mutants no longer produced amino acid (implies particular enzyme no longer functions)
Tested; If loss of function had genetic basis→ crossed mutant with normal mould; found offspring shared mutant phenotype→ inability to produce amino acid is inherited (due to mutation)
Found different enzymes in different mutants altered or missing; proved gene determines structure of enzyme→ proposed one gene-one enzyme hypothesis
Changed to one-gene-one protein when demonstrated other proteins besides enzymes encoded by gene
Found one gene not necessarily responsible for structure of entire protein; but for each polypeptide chain making up protein (currently accepted)
Explain the relationship between proteins and polypeptides
Proteins: Amino acid chain joined by peptide bonds; may be from many polypeptide subunits
Polypeptide: Molecule consisting of many joined amino acids→ aa joined by peptide bonds
To make particular polypeptide, amino acids must be
linked up in a precise sequence
Genes store info needed for making polypeptides→ info is stored in coded form
Precise sequence of bases in gene codes for the sequence of amino acids in a polypeptide
Explain how mutations on DNA may lead to the generation of new alleles
Mutagens are environmental agents that cause mutations;
Chemical (asbestos), Biological (HIV), Mutagenic radiation (UV, nuclear reaction)
Changes to genetic material arise during DNA replication
Mutations alter genes; change nucleotide sequence in DNA→ One or more genes may be altered from original form (Allele 1, Allele 2) 2 variations of gene is formed→ new allele formed
One or more genes may be altered from original. E.g,
Allele 1→ altered polypeptide→ new protein
Most new proteins have little effect on organism, but some lead to genetic disorders, inherited diseases
Effect of new proteins on next generation:
If mutation in a somatic cell→ individual may be affected but no effect on future generations
If mutation is in germline cell (gametic mutation) →
alleles can be inherited and have significant effects on population→ result in evolution
Changes to genetic material arise during DNA replication→ result in Change to single gene (gene mutation) or rearrangement of blocks of whole chromosomes (chromosomal mutations)
Discuss evidence for the mutagenic nature of radiation
During late 1800’s and early 1900’s, many scientists were involved in studying radiation
Harmful effects of radiation were unknown→ scientists such as Marie Curie who were exposed to large amounts of radiation over a prolonged periods of time, developed various illnesses
Marie Curie worked with ionising radiation for most of career; died from leukemia (overexposure)
Survivors of Hiroshima bomb→ suffer physical mutations (radioactive output of nuclear explosion)
Explain how an understanding of the source of variation in organisms has provided support for Darwin’s theory of evolution by natural selection
Mutation; basic source of variation
Mutations affect base sequence of DNA→ understand how can be passed from one generation to next→ supports Darwin’s theory of evolution (Explains how heritable variation arises)
Mutation will result in change in phenotype, may not do anything, or may confer advantages disadvantage to organism
Mutations provide diversity of genetic material that results in variation in phenotype
If mutations can be inherited→ provide variation on which natural selection acts
Evolutionary purposes, mutation can be redefined as heritable change in genetic material
Process and analyse information from secondary sources to explain a modern example of natural selection
INSECTICIDE RESISTANCE
Majority of mutations; detrimental to or have no significant effect on environment; some beneficial
Some organisms→ developed resistance; most killed, some naturally resistant survive and reproduce (pass genes→ resistant pop develops)
E.g. Sheep blowfly lay eggs in wet wool; burrow into skin→ loss of production → developing resistant to agricultural insecticides
If insecticides rotate, effectiveness increased
Process and analyse information from secondary sources to explain a modern example of natural selection
ANTIBIOTIC RESISTANCE
Many bacterial infections treated with antibiotics. Interfere with protein synthesis
Many bacteria become resistant to wide range of antibiotics
Animals given antibiotics to grow faster and not have disease→ if humans eat or drink milk from animals, then resistant bacteria could be transferred to humans
Encouragement of doctors to restrict general use of some selected antibiotics
Describe the concept of punctuated equilibrium in evolution and how it differs from the gradual process proposed by Darwin
Theory; Evolution occurs in short bursts of rapid change, followed by longer periods of stability
If evolutional change is gradual, could be predicted; fossilised remains showing these ongoing changes
Darwinists use traditional forms to support perspective of gradualism→ gradual change over an extremely long period of time
Many fossilised remains show millions of years with no noticeable evolutionary change to species
E.g. Soft bodied organisms dominates seas for hundred of millions of years and in period of million years disappeared and were replaced by organisms with shells and skeletons
Supporters of punctuated equilibrium argue if evolution occurs gradually, as proposed by Darwinists there should be greater diversity among living organisms that exist
Fossil records is incomplete so difficult to come to an agreement on evolutionary change
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
Scientists associated with double helix discovery; Rosalind given no recognition
Franklin; find out structure of DNA molecule (X-ray crystallography) → Identified A and B form
Work provided without knowledge or consent to Cambridge competitors through Wilkins; used her data to build model
Maurice Wilkins→ studied diffraction images and discovery of patterns to guess molecular DNA structure
Wilkins, Franklin diffraction images→ discovery of 3D helical nature
Crick and Watson analyse Franklin/Watson crystallography; realised DNA structure was helix
Processed info from other, manipulated model→ Watson and Crick discovered fmoud double helix
Watson, Crick and Wilkins won Nobel Prize (1962) for work in DNA→ Franklin wasn’t honoured and appropriately acknowledged→ already dead
Identify how the following current reproductive technologies may alter the genetic composition of a population:
ARTIFICIAL INSEMINATION
Sperm taken from chosen male; inserted into selected females
Cost effective; frozen sperm transported; not animals(reduce injury danger)
Sire several offspring with different females; conservation of species→ but reduces genetic diversity
Bred selectively; alleles increase in gene pool selected by breeder not nature
Survival and reproduction in pop→ depends on alleles that are useful to humans, not environment
Identify how the following current reproductive technologies may alter the genetic composition of a population:
ARTIFICIAL POLLINATION
Remove stamens; dust pollen onto stigmas of another flower or same flower; E.g. Mendel pea plants
Greater degree over breeding process; ensures pure breeding→ but less genetic diversity; species vulnerable to sudden environment change
Identify how the following current reproductive technologies may alter the genetic composition of a population:
CLONING
Reproductive cloning: Genetically identical fully developed organism using cell from other organisms
Therapeutic cloning: Cells from individual to produce cloned early embryo
Gene cloning: Producing identical copies of a gene E.g. Dolly the sheep, Bananas, twins
Characteristics can be precisely bred→ conservation; reintroduce extinct genes, endangered animals
Reduces genetic diversity; increases risk of being wiped out from sudden environmental change
Not natural→ need to ‘switch on” genes and most experiments fail
Organisms; genetically identical→ reduced variability
Process information from secondary sources to describe a methodology used in cloning
Somatic Cell Nuclear Transfer→ SCNT→ 3 animals; nucleus donor, egg donor, surrogate mother
Somatic cell nucleus transferred to egg without nucleus; reprogrammed to become zygote and grows
E.g. Dolly the sheep; cell from 6 yr old ewe udder→ injected into enucleated second sheep cell; fused with electricity→ grow and develop normally→ injected into third sheep uterus
Sheep born dentic twin to sheep donating egg
Transgenic species:
A species that has genes transferred into its genetic code from another species
Examples of use of a transgenic species and reasons for use
EXAMPLE:
Gene from bacteria has been transferred to cotton called BT cotton→ Gene codes for bacterial protein called BT toxin that kills Helicoverpa moth→ major pest of cotton crop
REASONS FOR USE:
Use of less insecticide on BT cotton crop→ benefits farm workers and wildlife
Increase in crop yield
Reasons for transgenic species use
DNA and proteins of transgenic organisms unlikely to cause any problems as digested in human gut
Research suggests transgenic species don’t survive long in natural ecosystems and if genes transfer to wild species, natural selection acts against them
Transgenic techniques will reduce cost of food production, which benefits producer and consumer
Transfer of genes between species is natural phenomenon.
Reasons against transgenic species use
Impossible to be certain about long-term health effects of genes in GMO foods or proteins made using genes
Genes could escape and be transferred to wild plants or animals. E.g. Possibly creating superweeds
Will allow multinational companies that develop them to become too powerful
Infringement of rights of every species to independently exists and could cause suffering in animals
Outline the processes used to produce transgenic species and include examples of this process and reasons for its use
Pronuclear Injection
DNA can be introduced directly into an animal cell by microinjection
Multiple copies of desired transgene are injected via a glass micropipette into a recently fertilised egg cell→ then transferred to surrogate mother
Not efficient; many don’t survive
Outline the processes used to produce transgenic species and include examples of this process and reasons for its use
“Gene gun” Ballistic DNA injection
Foreign DNA into living tissues literally shoots directly into organism using “gene gun”
Microscopic particles of gold or tungsten are coated in
DNA and propelled by burst of helium into skin and
organs of animals and tissues of intact plants
Some of cells express introduced DNA as if it were their own.
Outline the processes used to produce transgenic species and include examples of this process and reasons for its use
Transfer using virus or bacteria to carry DNA of the gene
E.g. Insulin
Messenger RNA coding for insulin is extracted from human pancreas cells that make insulin
DNA copies of messenger RNA made and sticky ends are made by adding extra G nucleotides to gene ends
Plasmids are small loops of DNA found in bacteria→ cut open using restriction enzymes and sticky ends made by adding C nucleotides at ends of cut plasmid
Insulin gene and plasmid are mixed. Link by complementary base pairing (G-C) between sticky ends
Plasmid with human insulin gene inserted is called recombinant plasmid
Suitable host cell is chosen to receive gene. E.g. E. Coli bacteria
Recombinant plasmid are mixed with host cells.Host cells absorb them
Genetically modified E. Coli are cultured in fermenter
E. coli bacteria start to make human insulin which is extracted, purified and used by diabetics.
Discuss the potential impact of the use of reproductive technologies on the genetic diversity of species using a named plant and animal example that has been genetically altered
CLONING
Decreased genetic diversity;only one parent; identical to one parent
Desired characteristics evident;individual control and reproduced in short time
All identical→ less likely to survive sudden environmental change, foreign pathogens
May be used in conservation with endangered or extinct animals
