Genetics & Biotechnology

Selective breeding occurs when we (humans) breed organisms with certain traits to produce offspring with desired traits.

A method of selective breeding

Crossing parents with different traits to produce offspring that are hybrids of the parents

The goal is to get certain traits in the hybrids that aren’t in either parent

Can take a long time (expensive)

A method of selective breeding

Closely related organisms with desired traits are bred to keep the desired traits and remove unwanted traits in the offspring

Not all undesired traits may be removed - sometimes harmful recessive traits show up in the offspring populations

Genotype = alleles (versions) of a gene present in the genome of the individual

When an individual's genotype is not known, a test cross can be used

Test cross = unknown individual is crossed with a homozygous recessive for the desired trait

An alternative to selective breeding

Manipulate the DNA to select for traits in offspring

Adding DNA from another organism

Goal: isolate the gene from the genome and manipulate the DNA (decrease/increase expression of that gene)

Restriction enzymes = enzymes that cut DNA into fragments by recognizing certain DNA sequences

Gel electrophoresis = separates DNA fragments by size

DNA fragments are loaded into a gel

An electrical current causes the negatively charged DNA to move through the gel

Smaller DNA fragments travel further/faster than larger fragments

Once the fragments of DNA (genes) have been cut out of the genome and separated, we can combine them with other fragments/genomes

Once combined, we can replicate the recombinant DNA for further study

A technique for replicating recombinant DNA

The DNA is recombined in a plasmid (withing a bacterium)

When the bacterium replicates, so does the plasmid (and the gene)

Polymerase Chain Reaction is another method of replicating the gene

PCR can make multiple copies of 1 gene from a single template

A tool used to study the isolated gene

Once the sequence (A,G,T,Cs) of a gene is known, its function can be inferred by comparing it to known genes with similar sequences

Biotechnology is the application of genetic engineering to genetic problems

Organisms that contain DNA/genes from other organisms are called transgenic organisms

Animals are commonly used to study diseases

Plants are commonly used to study disease and pest resistance