Transcript Biology 4.35 Human Intervention

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:
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Disease eradication
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Disease treatment
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Increased crop yield
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Increased food production
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Allow infertile individuals to reproduce
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Increase knowledge and understanding of evolution
Mechanisms for Intervention
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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 horsefamily clone.
• Horse: Prometea, a Haflinger female born 2003-05-28, was the first
horse clone.
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
Transformation
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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
taken by chorion villus sampling or amniocentesis.
foetus a sample is
• 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 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.
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.