Upload
jacob-ellis
View
221
Download
3
Tags:
Embed Size (px)
Citation preview
Chapter 13 – Genetic Engineering
L2 Biology
Has Bonnie been bred by selective breeding?
Selective Breeding• Choose organisms with the desired traits
and breed them, so the next generation also has those traits
• Nearly all domesticated animals and crops
• Luther Burbank (1849-1926) developed >800 diff varieties of plants in his lifetime
Hybridization
• Breed two dissimilar organisms
• In plants – often results in better lines – hybrids are larger, stronger, etc
• In animals – hybrids produced may be weaker and sterile
– Ex – wolf x dog ---- weak wolf-dog
– Ex – horse x donkey ---- mule (sterile)
Horse x Donkey = Mule
Lion x Tiger = Liger
Inbreeding
• Breeding two organisms that are
very similar to produce offspring
with the desired traits. – Ex – dog breeds
•Risks – might bring together two individuals that carry bad recessive genes – many purebred dogs have genetic disorders that mutts don’t get.
Increasing Variation• Induce mutations – the ultimate source of
genetic variations among a group of organisms– Mutagens used – radiation and chemicals– Some organisms are formed that have more
desirable variations.
Producing new kinds of bacteria
• Can expose millions of bacteria at one time to radiation – increases chances of producing a successful mutant. – Ex – bacteria that can digest oil have been
produced this way
Producing new kinds of plants:
• Drugs that prevent chromosomal separation in meiosis have been used to create plants that have more than two sets of chromosomes (2n). These are called polyploid plants. – Ex – bananas, citrus fruit, strawberries, many
ornamental flowers
Diploid corn
Tetraploid corn
Manipulating DNA – tools of the molecular biologist
• DNA extraction – open the cells and separate DNA from all the other cell parts. – Remember the kiwi lab?
• Cutting DNA
• Use restriction enzymes
– each one cuts DNA at a
specific sequence of nucleotides.
• This will make different
lengths of DNA
• Separating DNA – Gel Electrophoresis– Place fragments at one end of a porous gel – we
use agarose gel– Apply an electric current – The DNA is
negatively charged and will travel toward the positive end of the gel.
– The larger pieces of DNA move slower, the smaller ones faster.
– Used to compare genomes of different organisms or different individuals.
– Also used to locate and identify one particular gene out of an individual’s genome.
Click here for animation about gel electrophoresis
Using the DNA Sequence
• Sequence can be read, studied, and changed.
• Techniques used to study DNA sequences: – Use DNA polymerase and the 4 DNA bases to
produce a new DNA strand complementary to unknown strand – some of the bases are dyed.
• Dye-labeled strands are then separated using gel electrophoresis and the order of the bands tells the DNA sequence of the unknown strand.
• Cutting and Pasting – make recombinant DNA (DNA from two different organisms).
– Cut out the gene to be inserted, use same restriction enzyme to cut the receiving DNA strand, attach the two DNA strands
Making Copies
• Polymerase Chain Reaction (PCR) is used to make many copies of the same piece of DNA like a photocopy machine makes copies of papers.
• This is useful if there is only a very small sample of DNA available (as that found in a small blood drop at a crime scene)
Cell Transformation
• A cell takes in DNA from outside the cell and that DNA then becomes part of the cell’s DNA.
• Bacteria – place DNA in the solution that bacteria live in, and some of that DNA will be taken in by the bacteria cells.
Bacteria Transformation using Recombinant DNA
• Cut a gene with a restriction enzyme out of a human cell (ex – gene for insulin or growth hormone work well)
• Cut a bacterial plasmid using the same restriction enzyme (DNA ends will be complementary)
• Insert Human gene into bacterial plasmid• Insert plasmid back into bacterial cell• Bacteria will multiply, and all offspring will have
that gene – these bacteria will then follow the directions of the human gene and make the protein coded for (insulin or human growth hormone)
Transforming Plant Cells
• Use bacterial plasmid to insert desired gene into DNA of a plant
Transforming Animal Cells– Directly inject DNA into the nucleus of an egg
– it will become part of the chromosomes.
• Has been used to replace specific genes.
Glowing mouse cells in embryos that were made from sperm given the gene for bioluminescence from jellyfish – now all the cells glow!
Applications of Genetic Engineering
• Gene for luciferase was isolated from fireflies and inserted into tobacco plants – they glowed!
• Transgenic organisms – contain genes from other species
A transgenic mouse, which carriesa jellyfish gene, glows green underfluorescent light.
Transgenic Organisms
• Bacteria - Make human proteins like insulin
• Plants – 52% of soybeans, 25% of corn in US in year 2000. Some produce natural insecticide, some resist weed-killers, may soon be used to produce human antibodies; rice with vitamin A.
•Animals – mice with immune systems like humans; farm animals that grow faster and larger with extra copies of growth hormone genes; animals with leaner meat; chickens resistant to bacterial infections.
Cloning • Clone – member of a population
of genetically identical cells
produced from a single cell.
• 1996 – Dolly cloned –
1st mammal (sheep) cloned.
• She got arthritis several years
earlier than most sheep
• Died in 2003