MODULE 6. GENETIC CHANGE Flashcards
definition - mutagens
environmental agents which damage DNA
definition - mutations
permanent changes to the structure and sequence of DNA
effect of mutations
mutations produce new genetic variations via forming new possible alleles
definition - electromagnetic radiation sources
waves which carry electromagentic energy
high EM radiations cause…
atoms to vibrate and lose electrons - this breaks bonds, damaging DNA
EM radiation sources-
The sun - emits infrared, Uv light - causes mutations e.g. skin cancer
radioactive elements- e.g. uranium 236 - releases gamma rays as they decay - made in chemistry labs, nuclear bombs
medical imaging machines e.g. X-ray, PET scanner
How can chemicals cause mutations
chemicals can accidentally incorporated into DNA, instead of proper nucleotides. e.g. 5-bromodeoxyuridine
DNA polymerase accidentally incorporated 5-BDU into DNA
Chemical insert itself into the DNA. e.g. actinomycin D. creates a bulge in the DNA which prevents replication
chemical makes gaps in the DNA e.g. dimethyl suphate . breaks the bond base and sugar
naturally occurring mutagens occur in:
microbe
plant
animals
naturally occurring mutagens: MICROBES
mycotoxins are poisonous chemicals produced by fungi e.g. aflatoxin B1 - inserts itself into DNA and distorts it
naturally occurring mutagens: PLANT
cyasin is a mutagenic chemical, found in cycad plants
naturally occurring mutagens: animal
Dimethyl nitrosamine is produced in the stomach when nitrate is consumed.
defintion - point mutation
point mutations involve a change within a gene in which one base pair in the DNA sequence is altered.
Addition, deletion, or substitution occurs
what are point mutations a result of?
mistakes made in DNA replication
however they also occur through X-rays or UV radiations
Point mutations may involve:
- base subsitiution: one pair of nucleotides (e.g. A-T) is substituted for another pair
Frame shift - extra bases are added to or deleted form a strand of DNA, changing the whole sequence of nucleotides
types of base subsitiution (point mutations)
SILENT - there is no change to amino acid sequence in the polypeptide - no effect
MIS-SENSE - there is a change to the amino acid sequence in the polypeptide - effect= incorrect polypeptide
NONSENSE - there is a premature stop codon, which shortens the polypeptide and so usually results in a non-functional protein, effect= shorter and incorrect polypeptide chain-produces a stop codon
what are frame shift mutations
extra bases are added to or deleted from a strand of DN, changing the whole sequence of nucleotides - effect = incorrect polypeptide
e.g.s of point mutations
SICKLE CELL ANAEMIA - recessive disorder caused by a single substitution in the gene that creates haemoglobin. When people have two copies of this mutation, it results in thin sickle-shaped blood cells that sometimes cannot carry oxygen properly
CYSTIC FIBROSIS - results in the loss of amino acid and causes an incorrectly folded protein (this deletion is not a frameshift mutation because three bases next to each other are deleted, and all the other amino acids in the chain remain the same)
what does chromosomal mutations involve
Chromosomal mutations involve structural or numerical changes to chromosomes. They differ from gene mutation and in many cases creates a more dangerous affect
chromosomal mutations: numerical abnormalities
- Numerical abnormalities, when an individual has an extra chromosome or is missing a copy of a chromosome. E.G. down syndrome.
chromosomal mutations: structural abnormalities
chromosomal mutations: chromosomes having chunks deleted, duplicated or translocated from one chromosome to another, or chromosome being inverted to face the opposite direction.
processes that occur in chromosomal mutations
duplication
inversion
deletion
translocation
chromosomal mutations: duplication
a process of the chromosome is duplicated resulting in extra genetic material
effect =pushes all nucleotides out of order - incorrect polypeptide
E.G. downsyndrome - a disorder related to physical growth delays, characteristic facial features and often intellectual disability due to the presence of an extra chromosome 21
chromosomal mutations: inversion
a portion of the chromosome has broken off, turned upside down, and reattached within itself, therefore genetic material is inverted
effect = incorrect nucleotide order
chromosomal mutations: deletion
A portion of the chromosome is missing or deleted.
–> occurs from errors in crossover in meiosis
effect= shorter polypeptide
E.G. partial deletion in the short arm of chromosome 4 causes wolf-Hirschhorn syndrome that causes a distinct craniofacial phenotype and intellectual disability
chromosomal mutations: translocation
a portion of one chromosome de-attaches and is transferred to another chromosome
effect= changes in nucleotide sequence of chromosome = incorrect functioning
what are germ line mutations
Occur in germ cells which become gametes and affects offspring of the individual
what are somatic mutations
Occur in body cells during mitosis and only affects the individual
effect of germ-line mutation
Mutate offspring and introduce new alleles into a population.
Often results in sterility as they are in the sex cells
effect of somatic mutations
Error in DNA = more susceptible to developing cancer, but are not passed on to the next generation
what is the function of coding DNA
codes for and produces amino acids and polypeptides
what is the function of non-coding DNA
Does not code for amino acids and polypeptides but is essential for proper cell functioning.
what happens if there is a mutation in coding DNA
Genetic diseases
what happens if there is a mutation in non-coding DNA
Mutations in non-coding DNA have been linked to development disorders such as isolates Pierre Robin sequence, which is caused by changes in enhancer elements that control the activity of the SOX9 gene.
Non-coding DNA mutations have also been associated with several types of cancer
what % of DNA is non-coding
98%
what are the 3 causes of genetic variation
mutation
meiosis
fertilisation
causes of genetic variation: mutation
This provides a source of new variation, either somatic or germ line mutation introduce new alleles.
The changes cause genetic variation in a number of ways including:
- Adding or removing parts of gene creates defective protein or might create a less functioning protein with a deviant structure.
- Silencing genes that can eliminate a particular trait.
- Adding, deleting, translocating chromosomes causing disorders in organisms, some of which are untreatable and lethal.
- Mutations can also produce different products from similarly sequenced mRNA transcripts.
causes of genetic variation: meiosis
Crossing over is the process by which the allele of different gene on the same chromosome are recombined during meiosis.
Variation is further increased when cells divide during meiosis, where homologous chromosomes are randomly distributed, separating independently of each other. This is called independent assortment. It results in gamete that have unique combinations of chromosomes.
Independent assortment of genes during meiosis shuffles them.
causes of genetic variation: fertilisation
during fertilisation a zygote receives half of the genotype from the mother and the other half from the father - the way their genes interact can determine the production of traits
this involves the random fusing of genetically recombined gametes during fertilisation increasing genetic variation
definition: gene pool
all genes in a popuolation
definition: genetic drift
random change in allele frequency by chance (unlike natural selection which is not based on chance but on which alleles are more favourable)
definition: gene flow
passing on genetic material from one population to another
effect of mutation on the gene pool of populations
mutation is the prime source of genetic variation and when mutations occur in germ cells, they become inherited and will pass from the part to the offspring
how can mutation INCREASE a gene pool
if the mutation helps the organism survive
E.g. antibiotic resistance of bacteria. - mutation in bacterial species and once they are passed over to the next generations, a huge population of bacteria might become resistant to specific antibiotics
how can mutation DECREASE a gene pool
A DECREASE in gene pool may also occur if a mutation turn lethal and can cause extinction of a certain population because in allele number in one population will gradually increase the possibilities of the same event to occur in the following generations and at some point, the population will not have enough variation to survive.
effect of gene flow on the gene pool of populations
Gene flow is the transfer of genetic variation from one population to another.
Gene flow can bring new alleles int a population which occurred by chance accelerating microevolution. It may therefore increase ‘fitness’ of a population and increase their survival rates.
effect of genetic drift on the gene pool of populations
Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance. Soe random event, such as a natural disaster, destroys a large portion of the breeding population, and therefore allele frequency.
list social implications and ethical uses of biotechnology
- harm to the environment
- bioterrorism
social implications and ethical uses of biotechnology: harm to the environment
- Whether a GMO (genetically modified organism) may or may not cause harm to the environment and its adaptability with the changing climatic conditions still cannot be predicted. In some cases, the effect of the existence of a GMO on other organisms raises questions too. For example, A strain of corn has been created with a gene that encodes a natural pesticide. On the positive side, the transgenic corn is not eaten by insects, so there is more corn for people to eat. The corn also doesn’t need to be sprayed with chemical pesticides, which can harm people and other living things. On the negative side, the transgenic corn has been shown to cross-pollinate nearby milkweed plants. Offspring of the cross-pollinated milkweed plants are now known to be toxic to monarch butterfly caterpillars that depend on them for food. Scientists are concerned that this may threaten the monarch species as well as other species that normally eat monarchs.
social implications and ethical uses of biotechnology: bioterrorism
- Governments are worried that terrorists will use biotechnology to create new Superbugs, infectious viruses, or toxins, for which we have no cures.
what is a further direction of the use of biotechnology
CRISPR-Cas9
what does CRISPR-Cas9 do
Combination of RNA sequence and restriction nuclease that has enabled precise gene editing by inserting, replacing, deleting or regulating genes
steps of CRISPR Cas9
- RNA guide of 20 nucleotides that match specific bases of the target DNA locate correct point on chromosome
- Cas9 enzyme cuts both DNA strands
- Cell attempts to repair the break
- Chain of nucleotides carried by CRISPR-Cas9 inserted to render desirable change
uses of CRISPRcas9
- Prevent vector mosquitoes from transmitting diseases (e.g. malaria)
- Germ-line editing – fixing genetic disorders in embryos (e.g. cystic fibrosis), choosing desirable characteristics in children (e.g. 20/20 vision, high IQ, hair colour)
- Removing proteins that code for high allergy risk (e.g. changing proteins in eggs which are recognised by immune system to cause allergic reaction in some people)
- Creating decaffeinated coffee beans by turning off the genes which code for caffeine – saves time and money compared to current decaffeination process
list potenial benefits for society of research using genetic technologies
- less starvation and malnutrition
- less environmental damage because of more efficient food production
- increased life expectancy and quality of life because of personalised medicines and management of health
- sustainable resources (e.g. waste management, less pollution)
positives of less starvation and malnutrition
Better vitamin and mineral consumption in high risk countries
- Increased life expectancy in developing countries
- Fruits and vegetables cheaper to encourage consumers = less obesity in developed countries
negatives of less starvation and malnutrition
Cheaper foods extend into unhealthy foods = more obesity in developed countries
- Equitable distribution of resources difficult to manage (i.e. high-risk countries should have more access)
- Increased human population = increased environmental stress
positives of less environmental damage because of more efficient food production
Possible recreation of previously destroyed ecosystems
- Less need for destruction of crops/trees – more efficient
negatives of less environmental damage because of more efficient food production
- Testing of unsuccessful foods = damage to environment and food wastage
- GM alone won’t have dramatic impact on environment – people’s habits must change
positives of Increased life expectancy and quality of life because of personalised medicines and management of health
Quicker treatment and less side effects
- Better understanding of gene function and causes of disease
negatives of Increased life expectancy and quality of life because of personalised medicines and management of health
Increased strain on aged care
- Research very expensive
- Trials required on animal and human test subjects – risks
positives of Sustainable resources (e.g. waste management, less pollution)
- More renewable options for increased demand and human population
negatives of Sustainable resources (e.g. waste management, less pollution)
- Requires changes to human behaviour (e.g. less motor use)
- May require further modifications – expensive (e.g. engines)
positive changes of GM to biodiversity
o De-extinction becoming a possible option
o Gene-editing tools help endangered species cope with change
o Possibility of saving whole ecosystems (e.g. coral reefs)
o More efficient use of bio-resources (e.g. biofuels/ethanol)
negative changes of GM to biodiversity
o Adverse effects on non-target populations (e.g. Bt cotton impacts bees pollen collection)
o GM crops may affect soil by decreasing rate of decomposition of organic wastes – decreases diversity of soil microbial populations
o Use of plant material for pharmaceuticals increases pressure on plant = overexploitation and species loss
o Loss of species and habitat diversity
strategies to reduce the impact of GM on biodiversity
o Seed and gene banks to preserve genes of wild endangered species
o Captive breeding programs to nurture disease free populations
o More humane ways of controlling feral/exotic species
list gene technologies that induce genetic change
knockout gene (KO gene)
Marker-assisted breeding
Genetic screening and IVF
gene technologies that induce genetic change: KNOCKOUT GENE - USES AND ADVANTAGES
- Used to study gene function by comparing KO with normal organisms
- Mice frequently used as KO animals because of similarities to humans
Helped understand human disease (e.g. cancer, obesity, heart disease, substance abuse, Parkinson’s)
gene technologies that induce genetic change: MARKER ASSISTED BREEDING - USES AND ADVANTAGES
Helps select organisms for selective breeding
- Combined with viral screening, it helped tiger prawn aquaculture to develop breeds tolerant to diseases
- Speeds up selective breeding
- Increased pond yield of black tiger prawns by 50% = more sustainable
gene technologies that induce genetic change: GENETIC SCREENING AND IVF- USES AND ADVANTAGES
- Embryos can be screened and selected to avoid inherited diseases
Harmful germ-line mutations can be avoided in offspring
definition: artificial insemination
is the injection of male semen into a female of the same species – a technique often used by animal breeders.
list 2 reproductive technologies
- artificial insemination
2. artificial pollination
uses of artificial insemination
• Artificial insemination allows farmers to mate animals with the most desirable characteristics even when large distances are involved. For example, sperm from a prize bull can be transported and used to inseminate a large number of cows in distant locations. This means a much larger number of offspring can be produced than occurs in normal mating. The same applies to artificial pollination of plants. Pollen from the male stamens is collected and used to dust the stigmas. Again, plants with the most desirable characteristics are selected for breeding in this way. Both techniques can result in rapid and widespread change within populations of organisms
definition: artificial pollination
the dusting, often by hand, of fertile stigmas with the pollen from plants with desired traits
what are the two processes mechanical pollination can be done?
mechanical pollination
hand pollination
mechanical pollination
- Pollen grains are spread by a small aircraft or drone on a large area.
- Is not very efficient because the probes dust the pollen grains in the air and some pollen grains might not reach the flowers
hand pollination
- In this process human beings transfer pollen grains from one flower to another by the means of forceps
- More efficient as compared to mechanical pollination because pollen transfer is much more precise.
what are the types of cloning
whole organism cloning
gene coloning
what does whole organism cloning produce?
Produces MULTIPLE IDENTICAL COPIES of organisms with SELECTED CHARACTERISTICS.
what are two types of whole organism cloning
embryo splitting
somatic cell nuclear transfer
what does gene cloning produce?
identical copies of one gene
how does gene cloning work?
Produces MULTIPLE IDENTICAL COPIES of organisms with SELECTED CHARACTERISTICS.
two types of gene cloning
polymerase chain reaction (PCR)
gel electrophoresis
definition: recombinant DNA
DNA that has been artificially produced by combining DNA from two different species.
steps in recombinant DNA
- Required gene isolated from cell
- Piece of circular DNA, known as plasmid, is removed from bacteria
- 2 pieces of DNA are cut using SAME RESTRICTION ENZYME
- Fragments produced have matching sticky ends
- Bacterial plasmid cut at 2 points using SAME RESTRICTION ENZYME
- Sticky ends of human gene and plasmid come together and join by base pairing
- DNA fragments joined by DNA LIGASE
- Plasmid inserted into bacterial cell, where multiple copies of gene produced
what is a development transgenic organism in agriculture
golden rice
o 2 genes from daffodils, 1 from bacteria and DNA promotors added into plasmids
o Rice embryos infected and genes for making beta carotene are transferred
o Plasmids derived from soil bacteria
o During infection of host, bacteria transmits DNA to get expressed
o Transgenic rice crossed with local varieties to ensure adaptation to grow in local conditions
o Prevents/manages vitamin A deficiency – leads to night blindness and immune disorders
what is a development transgenic organism in medicine
knockout mice
o 4-day old embryonic stem cells carried into cell by modified viral vectors or bacterial DNA
o Cells cultured before implantation
o Microinjection of DNA into pronuclei of fertilised oocyte (before fusion of both gametes)
o Egg implanted into surrogate mother for development
o Inserted DNA may target specific gene and inactivate it or inactivate polypeptide synthesis to identify particular gene
o Used for research of human disease (e.g. cancer)
o Provides understanding of gene function and susceptibility to diseases
o Information on responses to various therapies
benefits of genetic tech. in agriculture
o Ability to rapidly and cheaply breed organisms for suitable for growth in changing environments (e.g. exposure to new diseases)
o More nutritious foods (e.g. golden rice)
o Less use of pesticides
o Less labour required
o Raise livestock more humanely
o Control gender of animals to increase productivity (e.g. female cows for milk production)
negatives of genetic tech. in agriculture
o Expensive for research
o Food wastage as result of unsuccessful trials
o Reduced animal welfare for testing
o Often used in developed countries instead of countries with high famine rates
benefits of genetic tech. in medicine
o GM vaccines safer as not made from denatured pathogens which risk infection
o Mass produce drugs (e.g. insulin)
o Better analytical techniques to detect substances and gene function
o Cancer treatment peptides stimulate ability of immune system to recognise difference between self and non-self-markers = more effective treatment and less side effects
negatives of genetic tech. in medicine
o Detriment of animals acting as test subjects for unsuccessful trials
o Expensive research and production
o Social controversy – natural way of life (e.g. anti-vax)
o Requires clinical trials on patients – risky
benefits of genetic tech. in industry
o Production of organic substances and proteins from transformed organisms (e.g. yeast – fermentation)
o Sensitive analytical procedures
o More renewable fuels – increase concentration and production of ethanol
o Biodegradable plastics promote recycling
negatives of genetic tech. in industry
o Destruction of crops/land for glucose (ethanol production)
o Factories creating fuels/products release greenhouse gas from production (e.g. distillation)
o Engines only able to hold specific amount of ethanol (e.g. 10% - E10) so engine modification needed after fuel becomes more renewable
what does biotechnology result in (in terms of biodiversity)
BIOTECHNOLOGY = LESS BIODIVERSITY
o GM plants with genes that produce insecticides reduce biodiversity because populations of target and non-target populations decline – insect eating birds at risk
o Biotechnology = improved human nutrition = longer lives = more impact on environment
o Genetic pollution – destroying natural gene pools by adding new genes = natural selection causes those without resistance to die
influence of social context on a range of biotechnologies
SOCIAL CONTEXT: Immediate physical and social setting in which people live or in which an event happens or develops.
o Lack of acceptance of GM foods – perception that farmers benefited and consumers at risk
o Pressure of gov. and regulators to increase consumer awareness of biotechnology
o Inconsistences in regulations and labelling requirements of GM foods
E.G. In 2002, 3 million people faces severe food shortages, and Zambian gov. rejected 32 000 tonnes of food because of the possibility it could be GM.
E.G. 2017 survey of 1200 Australians showed support for GM varied on type and purpose of the modification – support for medical (63%) vs. food (38%).
influence of economic context on a range of biotechnologies
ECONOMIC CONTEXT: Environment or situation relating to production, development and management of material wealth.
o Large companies have patents on GM foods = more money and ownership
o Small-scale farmers and developing countries have less access to GM seeds for crops as they are expensive and cannot afford them
o GM food can be cheaper for the consumer as it can be produced in bulk – farmers can produce greater volume for same price
E.G. In 1980, US Supreme Court ruled that a company could patent GM bacteria to clean up an oil spill – large sum of money for that company as they owned rights to that bacteria.
E.G. Between 1996-1999, 1.8 million cans tomato paste made from GM tomatoes were sold for 20% cheaper. Sales declined due to media attention, labelling regulations and misconception.
influence of cultural context on a range of biotechnologies
CULTURAL CONTEXT: Environment or situation relevant to beliefs, values, language, norms, shared attitudes and practices of the culture.
o Values of religious/moral beliefs and educational background influence opinions
E.G. Hawaiian variety of papaya genetically engineered to be resistant to ringspot virus. Plant is regarded as traditional to Hawaiian culture, so acceptance took time. After 50% of crop was lost to disease, acceptance became more wide spread.
E.G. European Union banned GM foods, whereas they are accepted in the US.
