PCR test and Genetic finger printing Flashcards
what is the purpose of a PCR test?
-it can create many copies of selected DNA in a very short time
what does PCR stand for?
-Polymerase Chain Reaction
what are the steps of the PCR test?
-DNA section heated to 95 degrees which breaks the hydrogen bonds to make it single stranded
-DNA cooled to 40-60 degrees which allows primers to bind to bind to each strand which are small strand that have complementary bases
-the primers jobs include stopping the DNA stands rejoining
-bracket the section of DNA that needs to be copied and they also stop DNA replication
-free nucleotides and DNA polymerase are are also added tp the strand
-the mix is heated again to 70 degrees
-DNA polymerase copies each strand, this polymerase is thermostable so it works rapidly at high temps
-the type of polymerase used depends on whether the dependence is on speed or accuracy of replication
-the two strand that are created are used as template strand to allow the process to continue again
when may the PCR test be used?
-forensic analysis
-medical research e.g. genetic screening and research reguarding genetic diseases
what are primers?
-short sections of DNA
-attach to the DNA strand to stop DNA replication, stop the strand rejoining and to bracket the section that needs to be replicated
what are the limitations of the PCR test, what could go wrong?
-if the DNA contains any type of contamination then even this will be copied too
what are the two ways that differences in the nucleotide sequence can be detected?
-gene sequencing/ working out the order of bases
-genetic markers
what is the basis of genetic screening in terms of genetic diseases?
-the identification that a particular sequence of DNA will indicate whether someone may have a genetic disease or not
what are the two types of gene markers that are used to show the differences in individuals nucleotides?
-MRSs Microsatellite repeat sequences
-SNPs Single nucleotide polymorphisms
what does MRSs stand for and what are they?
-Microsatellite repeat sequences
-the non coding section of DNA where a small number of bases are repeated
-the number of repeated bases vary between people
what does the difference in MRSs form in every individual? what is the term given to the amount of small sections that are repeated?
-it forms the basis of the genetic finger print
-the number of MRS repeats is also known as short tandem repeats
what does SNPs stand for and what does it mean? what is an example of a disease which is caused by a SNP?
-Single nucleotide polymorphisms
-one nucleotide differences between sections of DNA
-sickle cell anemia is caused by a mutation in just one of the nucleotides
what are the steps involved in genetic fingerprinting?
-DNA is extracted from an sample
-PCR test then occurs to amplify the amount of DNA for testing
-DNA is cut into different sized fragments using restriction endonuclease
-Primers are used to ensure that only the desired section is cut
-the fragments are then separated by gel electrophoresis into their different sizes
-DNA is either heat or alkaline treated to separate the strands
-fragments then transferred onto a nylon membrane by Southern Blotting
-DNA probes added, either radioactive or fluorescent (attach to complementary bases and if these bases aren’t present they will wash away)
-the labelled DNA is then added to an X-ray and the fingerprint can be seen
what are the 3 uses of genetic fingerprinting?
-criminal justice systems
-paternal courts
-used to show evolutionary relationships
what is the basic principle/ idea about what genetic fingerprinting shows?
-everyone has a unique genetic fingerprint but as relationships become closer the match also becomes closer
-the only people who have the same fingerprint will be identical twins
what is the risk of DNA fingerprinting/ ethical questions it raises?
-it is only effective if contamination is completely avoided
-the development of DNA databases also raises security issues
