Human Intervention in Evolution Aims: Must be able to state the possible reasons for Human intervention in evolution. Should be able to describe the different.

Human Intervention in Evolution

• Aims:

• Must be able to state the possible reasons for Human intervention in evolution.

• Should be able to describe the different mechanisms by which Humans can affect evolution.

• Could be able to explain in detail the affects of different Human interventions on evolution.

Reasons for Human Intervention

• The main possible reasons for Human intervention are:

• Disease eradication

• Disease treatment

• Increased crop yield

• Increased food production

• Allow infertile individuals to reproduce

• Increase knowledge and understanding of evolution

Mechanisms for Intervention

• The main mechanisms for Human intervention are:

• Selective Breeding

• Cloning

• Transformation

• Genetic Screening

• Gene Therapy

• Stem Cells

• Reproductive Technologies - IVF

Donor Eggs

Artificial insemination

Selective Breeding

• Examples: Cross breeding

Hybrids

Plants

Hardy crops

Increased milk production

Increased muscle meat

Development of finer wool

• Plants and animals which are allowed to breed are selected on the basis of traits desired by the farmer or breeder. Other organisms are prevented from reproducing

Artificial Selection

Evolutionary Consequences

• Changes in allele frequencies for both the selected traits and linked traits

• Increased numbers of homozygous organisms; Fewer heterozygotes can lead to general lack of vigour

• Less biodiversity leading to greater susceptibility of whole populations of organisms to pathogens and/or changes in environmental conditions

Cloning• Cloning of

organisms is the production of a new individual from a cell, nucleus or asexual offshoot of another organism. The clone is an exact genetic copy of the original organism

Cloning

• Plant tissue culture involves the production of many plants from the tissue of a single plant – there is no meiosis and/or fertilisation.

• Transformed bacteria are cloned to produce many copies of the bacteria carrying the desired gene.

• Cloning of animals is experimental only. It involves the replacing of the nucleus of a somatic cell (diploid) from another individual. The egg is then stimulated to divide producing a zygote with the genetic makeup of the donor of the nucleus

• Tadpole: (1952) Many scientists questioned whether cloning had actually occurred and unpublished experiments by other labs were not able to reproduce the reported results.

• Carp: (1963) In China, embryologist Tong Dizhou cloned a fish. He published the findings in an obscure Chinese science journal which was never translated into English.[5]

• Sheep: (1996) From early embryonic cells by Steen Willadsen. Megan and Morag cloned from differentiated embryonic cells in June 1995 and Dolly the sheep in 1997.

• Rhesus Monkey: Tetra (female, January 2000) from embryo splitting

• Cattle: Alpha and Beta (males, 2001) and (2005) Brazil[6]

• Cat: CopyCat "CC" (female, late 2001), Little Nicky, 2004, was the first cat cloned for commercial reasons

• Mule: Idaho Gem, a john mule born 2003-05-04, was the first horse-family clone.

• Horse: Prometea, a Haflinger female born 2003-05-28, was the first horse clone.

CloningEvolutionary Consequences

•Production of plants by tissue culture leads to loss of genetic variability in the plants (as in selective breeding)

•Animal cloning is experimental only at present (eg: Dolly the sheep). Should it become widespread in animal breeding, decreased diversity may result.

•A potential application of animal/human cloning is the production of cloned embryos from which embryonic stem cells, completely compatible with the donor of the nucleus, may be obtained. These may be able to provide a treatment for autoimmune, degenerative or cancerous diseases

Transformation• Gene transfer form one species to another:

• Examples: Transgenic crops

Canola, lettuce

GMO – vegetables, fruit

•Transgenic Organisms are organisms which carry and express a gene from another species. Genes have been inserted into crop plants (so that they gain a desirable feature such as disease resistance, firmer fruit, or resistance to herbicides), and into some animals

•The crown gall bacterium engineered or engineered pellets containing DNA can be used to introduce foreign genes into plant cells.

•Retroviruses, or direct injection of DNA into embryos can be used to produce transgenic organisms.

Tranformations

Evolutionary Consequences

• It is possible that genes from transgenic, or genetically modified (GM) crop plants will cross into non-GM varieties via dispersal of pollen and/or seeds. It is possible that the genes will spread to other species also via bacterial or viral infection.

• Greater pressure for farmers to use higher yielding or more resistant crop varieties can lead to the loss of older varieties from the crop plants’ gene pools, decreasing diversity.

Genetic Screening• Assessing genetic make-up of embryos

• Examples: Undesirable traits can be recognised

Inherited disorders identified

The effect on diversity?

What is the impact of the loss of a single allele from the population?

• Genetic Screening of individuals to assess whether they are carriers of a recessive condition or likely to develop a genetic condition in later life. Screening of embryos for chromosomal abnormalities and/or inherited conditions

• Blood or tissue samples are used to obtain DNA. In a foetus a sample is taken by chorion villus sampling or amniocentesis.

• Test include: karyotype analysis to detect aneuploidy, translocations or inversions; DNA sequencing to test for substitutions in a specific gene; determining the genotype of an individual by the use of restriction enzymes and gel electrophoresis.

Genetic ScreeningEvolutionary Consequences

•Decisions which individuals make on the basis of the results of genetic screening have the potential to change the human gene pool.

•A person who knows they are a carrier of a detrimental trait may choose not to have children

•Parents may choose to terminate a pregnancy if the foetus is shown to have a genetic abnormality or inherited disease.

•Screening prior to the implanting of embryos (using in-vitro fertilisation) leads to fewer offspring with genetic disorders.

Gene Therapy• Replacing faulty genes with healthy ones

• Examples: Identify faulty gene

Locate affected cells

Identify healthy version of gene

Deliver a new/healthy gene to the cells

• Gene Therapy involves the insertion of genes into individuals who have a genetic disorder in order to induce the production of a faulty or missing protein.

• Functioning genes are extracted from an unaffected individual and copied.

• The genes are the delivered to the somatic cells of people suffering from a genetic disease; eg: the lungs of cystic fibrosis sufferers, the bone marrow of SCID sufferers.

• The genes are delivered via a vector (a virus) or injected particles (biolistics)

Gene Therapy

Evolutionary Consequences

•Treatments for conditions such as cystic fibrosis and SCID mean that sufferers of these conditions survive longer and potentially produce more offspring than would have been possible without treatment.

•The frequencies of the alleles for these conditions may increase in the population.

Reproductive Technologies

• Use the information from pages 646 to 649 in the Textbook to make basic notes on, focusing on the effects on evolution:

• IVF

• Artificial Insemination

• Egg Donation

• Other Reproductive technologies

Activity

• Complete the questions from page ? In the Biozone book.