5. Current reproductive technologies and genetic ...

5. Current reproductive technologies and genetic engineering have the potential to alter the path of evolution

• identify how the following current reproductive techniques may alter the genetic composition of a population:– artificial insemination– artificial pollination– cloning

Reproductive technologies

• Technology used to improve reproduction– Selective breeding or artificial selection– Hybridisation – Artificial insemination– In vitro fertilisation – Cloning


• Artificial pollination– Aka selective breeding– Dates back to 870 BC– Used by Mendel in his pea

experiments


– Involves removing the stamens of a flower and dusting the pollen onto the stigma of the same flower (self-pollination) or another flower (cross-pollination)


• Selective breeding– Mating a male with one desirable characteristic

with a female with another desirable characteristic offspring with both characteristics


– E.g. Friesian (large quantities of milk) x with a Jersey cow (creamy milk) offspring which produce large amounts of creamy milk

– Disadvantages:• Breeding of undesirable traits (E.g. udders that are so

large that cows have difficulty walking)• High monetary and time costs


• Artificial insemination– Taking sperm from a chosen male and artificially

introducing it into several selected females– Advantages:

• Overcomes problem of transporting animals, only frozen sperm needs to be transported

• More cost effective• Safer for animals• Many females can be inseminated• Semen can be frozen indefinitely • Used for conservation


• In vitro fertilisation (IVF)– Fertilisation occurs outside the mother’s body.

Zygotes are grown to a certain stage before implanting into the mother or frozen.

– Used when parents have decreased fertility

Altering genetic composition of population

• Particular traits are selected for by the breeder

• New combinations of alleles arise which are then selected for and become the dominant alleles in the population

• Genes for infertility are now passed on, the opposite of natural selection

• Sperm banks may result in selection of traits• Long term decrease in genetic diversity

Cloning

• To make a copy:1. Reproductive cloning: creating an identical

whole organism (asexual reproduction)

2. Therapeutic cloning: producing an early embryo as a source of stem cells

3. Gene cloning: producing a copy of a gene for genetic engineering

• process information from secondary sources to describe a methodology used in cloning

Somatic cell nuclear transfer

• http://ed.ted.com/featured/MViO4vvy

http://ed.ted.com/featured/MViO4vvy

• outline the processes used to produce transgenic species and include examples of this process and reasons for its use

Transgenic organisms

• A transgenic organism is an organism in which a gene from another species has been introduced by genetic engineering

Producing a transgenic species

1. ‘cut’: a gene for a favourable characteristic is removed from the cell of an organism, using restriction enzymes

2. ‘copy’: multiple copies are made (called ‘gene cloning’)—this step is usually carried out in bacteria


3. ‘paste’: the genes are inserted (injected) into an egg cell of another species and after fertilisation become part of the newly formed organism’s DNA

4. The egg develops into a mature organism (a transgenic species) with the new gene


• In step 3, genes can be introduced in a number of ways:i. Microinjection of

DNA into egg cellsii. Biolistics or gene gun


iii. Electroporation uses an electric current to open up cells

iv. Transduction by a viral vector

GFP markers

• Green fluorescent protein markers are used to indicate successful gene integration

Example: Transgenic cotton

• Aka “Bt” cotton, as it contains a gene from Bacillus thuringiensis

• Collaboration between CSIRO and Monsanto


• Problem: Traditional pesticides used on cotton plants were becoming ineffective from pests such as the caterpillar of the Helicoverpa zeamoth Resistance to pesticide


• Bt cotton plants were genetically modified to contain a gene that codes for a protein that kills the caterpillar

• The gene originally came from the bacterium Bacillus thuringiensis


• Farmers don’t need to spray as much pesticides and only need to use narrow spectrum pesticides

• The protein produced from the Bt gene is a toxin which only affects caterpillars and are safe for humans and most insects


• Steps:1. Cotton seedlings are cut into small pieces and

grown in medium to develop into embryos2. The Bt gene is cut from the genome and

multiplied3. Another bacterium, Agrobacterium tumefaciens,

is used to transfer the Bt gene into the cotton embryos

4. the recombinant embryos then develop into full plants which carry the Bt gene

Uses of transgenic organisms

• It can also be used to:– create genetically modified (GM) foods which

have higher nutrients and yields (Golden rice)– create disease and pest resistant crops– treat disease (gene therapy)

• discuss the potential impact of the use of reproduction technologies on the genetic diversity of species using a named plant and animal example that have been genetically altered

Impact of genetic modification on diversity

• In the short term, creating transgenic species increases genetic diversity

• However, in the long term, it may decrease genetic diversity since the original genetic material of some organisms may be reduced or lost forever

• analyse information from secondary sources to identify examples of the use of transgenic species and use available evidence to debate the ethical issues arising from the development and use of transgenic species

5. Current reproductive technologies and genetic ...

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