Cloning, IVF and stem cells

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  • Created on: 15-11-13 21:00
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Conventional breeding techniques are...
o Laborious
o Unpredictable
o Time consuming
CLONE= an asexually produced, genetically identical line of cells or organisms
Natural cloning occurs in
o Bacteria
o Yeast
o Plants such as corms, suckers and bulbs
Embryo cloning
Genetically identical offspring
Helps farmers increase numbers of animals
Conserves rare breeds young embryos of young animals are bisected and transplanted into common
1. Eggs from high milk yielding cow fused with sperm from best bulls (in vitro fertilisation)
2. The fertilised egg divides into a ball of cells/embryo
3. Young embryo is split to produce more embryos
4. Embryos transplanted into surrogate cows
Nuclear transplants
1. Cells taken from tissues of the udder of a donor sheep and cultured in a medium which stops cell
division. Nucleus is removed
2. An unfertilised egg is removed from a different sheep (the recipient). The nucleus is removed, leaving an
empty egg cell
3. The donor and recipient cells fuse together using a gentle, electric pulse and are allowed to divide until
eightcell stage producing a ball of cells
4. Developing embryo is implanted into uterus of host sheep
5. Lamb born is genetically identical to the donor sheep
Enables desirable qualities to be preserved for future generations
Advantages of cloning
Cell culture is useful for producing cells in quantity e.g. cancer cells for cancer research or monoclonal
The production of a single, identical, genetic line of cells with desirable qualities may be used to
maintain genetic stocks
Disadvantages of cloning
Can be expensive and unreliable
Inadvertent selection of disadvantageous alleles
Progeny may suffer from unexpected, long term side effects such as premature aging.

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Tissue culture
Cells from young animals and cancer cells can be induced to grow in vitro
A few cells keep ability to divide even in adulthood e.g.
o New cells to heal wounds/replace worn out skin cells
o New blood cells
o New cells to replace worn out cells in digestive system
But... most are specialised e.g. nerve cells and these usually do not divide again.…read more

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Last 25 years has seen an increase in couples seeking help to conceive
Infertile couple= failed to conceive after 12 months
Before treatment couples are assessed to discover cause of problem
o 50% problems with female reproductive system
o 35% related to male
o Rest cause unknown (60% of these will conceive naturally within 5 years)
o 50% of females will eventually fall pregnant
1. Ovulation stimulated using hormones at a specific dosage causes several follicles to develop at once
2.…read more

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Cloning of plants
Cells taken from stock plants with desirable characteristics (commercial value)
Costeffective and is better than conventional methods as large numbers of plants can be
transported at an early stage of growth and so take up little space
Based on ability of differentiated plant cell to give rise to all cells of adult plant plants are
TOTIPOTENT. (Not phloem/xylem cells too specialised)
Tip of roots/shoots=meristems
o Cells divide here rapidly by mitosis so are known as growing points
1.…read more


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