IB Biology Genetic Modification and Biotechnology

PCR

Polymerase chain reaction

PCR process

Denaturation (high temperatures separate the strands of DNA), annealing (DNA primers attach to the ends of the strands), elongation (taq, a heat-resistant polymerse, copies the strands)

PCR function

Copies a section not an entire genome, amplifies small samples of DNA (useful for crime scenes), used for DNA profiling/species identification

DNA profiling definition

Compares sections of DNA between two organisms to determine paternity or relations

Gel electrophoresis

DNA sample elongated through PCR, restriction enzymes separate DNA into segments of base sequences, fluorescent marker attaches to a triplet base sequence, samples added to a GE chamber, electric current passes through and pushes fragments along, heavier fragments are left behind and so shows a banding pattern

DNA profiling in paternity

Analysis of two related organisms, usually parent and child, will show a 50% similar DNA profile, as children receive half of their DNA from each parent

Genetic modification

Taking genes from one organism and inserting them into the genome of another; this can be done as codons are universal and the pattern of amino acids code for the same polypeptides in all organisms

Restriction enzymes

Proteins that separate certain sections from DNA, creating fragments with specific sequences on either end of it

Gene transfer

Restriction enzymes separate a segment of DNA from the genome of an organism; the same restriction enzymes cleave into a plasmid, so that the ends of the segment of DNA and plasmid match; ligase joines these ends together; the gene is inserted into a host cell, this cell now expresses the gene

Bacillus thuringiensis (Bt corn)

A corn crop that has been modified with the gene of a soil bacteria that produces insecticidal toxins

Advantages of Bt corn

Don't need to use harmful chemical insecticides; increased land productivity (less crops succumbing to pests), increased hardiness and nutritional value

Disadvantages of Bt corn

Non-target organisms may be affected; increase of resistance to toxin in pests; accidental release of crop may result in competition with local plantlife; might cross-breed the gene with other varieties, disrupting ecological system

Monozygotic twins

Twins forming from one zygote; they are genetically identical

Artificial propagation

The production of new plants through encouraging the growth of a stem cutting

Factors affecting artificial propagation

Stem length, number of leaves on the stem, condition of soil and water, how the stem is cut, covering with a plastic bag (reduces transpiration, preventing the stem cutting from dying too quickly)

Somatic cell nuclear transfer (SCNT)

Remove the differentiated, diploid nucleus of a somatic cell in one organism; enucleate (remove nucleus) the egg cell; transplate the somatic nucleus into the enucleated egg cell; place the egg cell into the endometrium (lining of the uterus) of the host; offspring will be genetically identical to the somatic nucleus donor