AP bio biotechnology (unit 6b)

early examples of biotechnology

selective breeding, food preservation (drying/salting)

modern examples of biotechnology

medicine, gmo crops, using organisms to clean up environmental pollution

how does gel electrophoresis work?

DNA samples (negatively charged) run through a specific kind of gel that has an asymmetrical webbed structure, allowing shorter pieces to travel through quicker while longer pieces move slower. the samples are placed into wells on the negative side of the machine next to a ladder that contains pieces of DNA of given lengths so we know about how long each of our samples are. buffer is placed on the top to conduct charge. when the machine runs, opposite charges are conducted at both ends of the gel—a negative charge where we placed the DNA, and a positive charge where the DNA moves

electrophoresis separates molecules according to which two factors?

size and charge

what is pcr?

polymerase chain reaction; a method of copying certain genes of interest over and over again (amplifying them)

what are the steps of pcr

denaturation, annealing, and extension

denaturation

separates complementary strands of DNA by heating the sample, breaking the hydrogen bonds that hold the two strands together

annealing

specifies the region to be copied using lots of primers (of about 20 nucleotides) that attach to specific regions. the mixture is cooled to allow the primers to attach to the strand.

extension

copies the region specified by the primers. DNA polymerase finds the primers we added and constructs from 5’ to 3’ in order to make the complementary strand. (we use a special polymerase called Taq polymerase that won’t denature at high temperatures) the heating and cooling cycles of the process specified in the previous steps occur over and over again to multiply the copies of DNA and give us a rich sample of the gene of interest

what is CRISPR Cas-9?

a system that helps modify the genome of organisms to edit, insert, or knock out target genes.

what are SNPs?

single nucleotide polymorphisms; one single nucleotide that varies from another genome sequence

why are SNPs useful?

they help scientists find patterns and identify genetic contributions to certain conditions by helping them determine the regions of DNA that should be further investigated to identify the specific gene sequences associated with the different conditions

what is a plasmid?

an extra piece of circular DNA found mainly in bacteria cells that is not the main chromosomal DNA code. it is helpful to program these smaller pieces of DNA to transform larger pieces of DNA

what does it mean to transform an organism?

change/insert a gene to alter the phenotype of an organism

restriction enzymes

special proteins that are specifically coded to look for and cut specific regions/nucleotide sequences of DNA. they look for these sequences, and if they find them, they cut the DNA at this spot, forming two smaller pieces of DNA (that will travel faster through a gel) as opposed to one long piece (that travels more slowly through a gel)

how has antibiotic resistance emerged?

through genetic mutation, like any new trait. it is the result of a random mutation in the bacteria cells that is then selected for. when an individual takes antibiotics, they kill off the nonmutated bacteria cells but could leave behind the ones with resistant mutations (especially if they don’t take their whole round of antibiotics), effectively selecting for them.

what is bacterial transformation?

a process by which bacterial cells take up foreign DNA from external sources (only during specific times). can be incorporated directly into the bacterial chromosome or exist separately in the cytosol as a plasmid

uses for bacterial transformation

makes medicines, helps modify food, amplifies DNA

DNA sequencing (sanger)

chain-terminating versions of all four nucleotides with different dye colors are created and placed into a solution with regular nucleotides, the DNA of interest, and primers. basically, a bunch of rounds of PCR take place so that (hopefully) there has been a chain-terminating nucleotide (instead of a regular one) added at every spot along the sequence. these copies of different lengths are sent through a gel with a laser reader at the positive end to sort the fragments by length and read the color (by the terminating nucleotide) to determine the sequence of the nucleotides.