Genetics & Biotechnology

Selective Breeding

• Selective breeding – humans pick desired traits to go on to offspring

• Hybridization – using organisms with different traits to create more competitive one – creates “hybrid vigor”

• Inbreeding – 2 closely related organisms are bred to increase the frequency of desired traits & to eliminate undesired traits

• Gene technology is a prominent issue in health and biological sciences today. It is able to stir debate and save lives. A genome is the total DNA present in the nucleus of each cell.

The process of isolating a gene from the DNA of 1 organism and transferring the gene into the DNA of another is called genetic engineering. It involves building recombinant DNA, a molecule made from pieces of DNA from separate organisms.

What are GM’s?

• are a result of technology that has altered the DNA of living organisms (animals, plants or bacteria)

Other terms that mean the same thing:• Genetically engineered• Transgenic• Recombinant DNA (rDNA) technology

How does this differ from Mendel and his peas?

GM vs. Selective breadingSelective breading-slow-imprecise-modification of genes that naturally occur in the organismGM-very fast -precise -can introduce genes into an organism that would not occur

naturally!

Why do it?

• Rice- not high in essential nutrientsModification: – + daffodil genes and a bacterium = beta-carotene

content drastically increased – + genes from a french bean = double the iron

content.

• Tomatoes- Introduce genes to increase shelf life.

How is this done?: Transgenic tomatoes

Other applications• Potato - modified to produce a beetle killing toxin • Yellow squash – modified to contain viral genes that

are resistant to the most common viral diseases• Develop foods that contain vaccines and antibodies

that offer valuable protection against diseases such as cholera, hepatitis, and malaria

• Canola – modified to resist one type of herbicide or pesticide

Who Uses this technology

The Countries that Grow 99% of the World's Transgenic Crops

69%

23%

7% 1%

USA

Argentina

Canada

China

Conclusion

Genetic Modification:

or ?

GENE TECHNOLOGY TOOLS • To extract DNA, the cells

must be opened, their proteins are broken down, & the DNA is separated from the other cell parts. A restriction enzyme is used to cut DNA at specific sequences of nucleotides (such as ATTGCA, TATGCA, etc.).

• Gel electrophoresis is used to separate fragments of DNA to analyze them, to sequence them, or to make DNA “fingerprints.” It is important to know the sequence of DNA to discover the functions of genes & to compare different organisms.

• Plasmids – small, circular, double-stranded DNA inside bacteria & yeasts

• DNA ligase – enzyme used to “glue” pieces of DNA together

• Transformation – when bacterial cells take up recombinant plasmid DNA

• Cloning – making copies of the bacterial cells containing the desired genes

• DNA sequencing – deciphering the exact sequence of bases in a strand of DNA

• Nucleic acid probes – have complementary bases attached to fluorescent markers to find desired fragment of DNA – use “ATCG” probe to find “TAGC”

• Fluorescent dyes are used to color-code DNA during sequencing so that it will be possible to know which base was added last.

• This process has 4 distinct steps:1. Cleaving DNA - the gene to be transferred is cut out of the host2. Recombinant DNA - the DNA is put into the vector (carrier – can be viruses or plasmids)3. Cloning cells - a culture of bacteria is grown with the infected vectors and allowed to grow4. Screening cells - the bacterial cells with the preferred gene are found & isolated

• Recombinant DNA is used to make many pharmaceutical products – insulin, HGH, interleukins, taxol, interferons, EPO, etc.

Making Recombinant DNA

• You can get yeast cells or bacterial cells to make human hormones by inserting a gene into the yeast or bacterial cell’s DNA. During transformation, a cell takes DNA from outside the cell, that becomes part of the cell’s DNA.

The steps for transformation:• 1. Cut out the desired gene from human

DNA.• 2. Remove the plasmid (DNA) from the

bacterial cell & cut it open.• 3. Insert the human gene into the plasmid

(makes recombinant DNA).• 4. Insert the recombinant DNA into the

bacterial cell.

http://www.dnalc.org/view/15928-How-insulin-is-made-using-bacteria.html

• Genetic engineering is possible because of a universal genetic code.

A clone is a member of a population of genetically identical cells produced from a single cell.

• In a successful transformation, the recombinant DNA is inserted into one of the chromosomes of a cell. A foreign gene can be inserted into a plasmid of an organism to make the traits of the foreign gene show up .

Polymerase Chain Reactions (PCR)• PCR is used to make copies of a desired piece

of DNA (useful in forensics, DNA testing)• Steps of PCR:• 1) Place segment of DNA, DNA polymerase, primers,

& the 4 bases (A,T,G,C) in tube• 2) Denature the DNA (use heat & then cool it) with

primers (binds to DNA) - The primers join to DNA fragments via DNA polymerase & then adds the extra bases

• 3) Repeat 20 – 40 timeshttp://www.youtube.com/watch?v=2KoLnIwoZKU

Microarrays

• Microarrays are used to analyze all the expressed genes from an organism or cell. It uses tiny slides or silicon chips spotted with complementary DNA fragments of a particular gene. Genes that are active “glow” based on the color assigned to the cDNA.

• A transgenic organism is created when genes from one organism are inserted into cells from another organism. These transformed cells can then be used to grow new organisms (ex. - making tobacco glow like a firefly).

The Human Genome Project

• This project sequenced the 3 billion nucleotides that make up human DNA. The purpose of the project was to determine the location of the genes & then later to determine their function. Scientists discovered that less than 2% of all the nucleotides actually code for proteins used by the body – the rest are noncoding sequences.

DNA Profiling• DNA profiling is possible due to the variation in the

noncoding sequences of DNA. The fragments are separated using gel electrophoresis to discover distinct bands. Single nucleotide polymorphisms (SNPs) arise from single nucleotide differences among two individuals. Short tandem repeats (STRs) may also be used to detect differences between samples (ex. - repeats AGAT 10 times in one site). Restriction fragment length polymorphisms (RFLP) change the lengths of fragments & can change the size of bands used in the analysis.

Beneficial Gene Technology• HapMap Project – creates an international

catalog of common genetic variations in humans – used to locate diseases using haplotypes (sequences of genes on 1 chromosome)

• Pharmacogenomics – studies how genetic inheritance affects the body’s response to drugs

• Gene therapy – creates recombinant DNA viruses to infect cells with “healthy” DNA – not allowed in the US since 2003

To clone an organism:• 1. An egg cell is taken from an adult. • 2. The nucleus of the egg cell is removed.• 3. The nucleus of an adult cell from the animal

to be cloned is put into the egg cell.• 4. Normal cell division begins.• 5. The embryo is put into the uterus of the foster

mother.• 6. The cloned offspring is born.

• A clone is relatively the same as an identical twin.

• Transgenic plants may be used to produce human antibodies to fight disease & to create foods that combat malnutrition (ex. = rice that has Vitamin A added to it). Transgenic animals may be used to produce human proteins to treat diseases.