Human Intervention in Evolution

1
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.

2
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

3
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

4
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

5
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

6
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

7
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

8

• 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  unpublished experiments by other labs were not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)
  Brazil6
• 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.

9
Cloning

• Evolutionary 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

10
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.

11
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.

12
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.

13
Genetic Screening

• Evolutionary 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.

14
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)

15
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.

16
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

17
Activity

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