Molecular Genetics 7-12 Flashcards
What is forensic science?
The application of science to criminal and civil laws, mainly on the criminal side during criminal investigation, as governed by the legal standards or admissible evidence and criminal procedure
What are the three fundamental principles that fingerprinting follows?
1) A fingerprint is an individual characteristic - no two people have been found to have the same fingerprint pattern.
2) A fingerprint pattern remains unchanged for life, however the print itself may change due to permanent scars and skin diseases.
3) Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.
When was fingerprinting first used?
1892
What are the three specific classes for all fingerprints based upon their visual pattern?
Arch
Loop
Whorl
What is the arch fingerprint class subdivided into?
Plain arch
Tented arch
What is the loop fingerprint class subdivided into?
Radial loop
Ulnar loop
What is the whorl fingerprint class subdivided into?
Plain whorl
Central pocket whorl
Double loop whorl
Accidental
When was blood typing discovered and by whom?
1901
Karl Landsteiner
Who invented DNA fingerprinting and what had they actually been researching?
Alec Jeffreys
He was researching the myoglobin gene, but discovered simple tandem-repeat regions of DNA
What are simple tandem-repeat regions of DNA?
Short repeated DNA sequences within introns. There is a polymorphism of repeat lengths among individuals which arises from unequal pairing and crossing over between repeats.
When was the first DNA fingerprint produced?
September 1984 in Leicester University
When was the first immigration case solved by DNA fingerprinting?
1985 - proved child belonged to certain parents entering the country
When was the first paternity case solved by DNA fingerprinting?
1985
When was the first identification of identical twins solved by DNA fingerprinting?
1985
When was the first criminal investigation solved by DNA fingerprinting?
1986
What are simple tandem-repeats also known as?
Minisatellites
What are the features of minisatellite DNA sequences?
1) Highly polymorphic
2) Stable within a lifetime
3) Inherited by offspring
4) Measurable by gel-based techniques
What size are minisatellites compared to microsatellites?
Larger
What is DNA fingerprinting?
A forensic technique used to identify individuals by characteristics of their DNA
How do minisatellites vary within individuals?
DNA sequence
Length of repeats
How is DNA fingerprinting used in criminal investigations?
To match DNA obtained from a crime scene to suspects
Multiple minisatellites will be used in actual criminal investigations to increase accuracy
What is the downside of DJA fingerprinting?
Relatively large amount of DNA needed - 50-250ng (several thousand cells)
Not ideal for forensic evidence with small degraded samples
The four steps of minisatellites typing:
1) Extract and purify DNA
2) Carry our PCR
3) Run PCR product on genetic analyser
4) Assign genotypes
What is multiplex PCR?
Amplifies multiple pieces of DNA in one PCR mixture using multiple sets of forward and reverse primers, one for each DNA template
Advantages of minisatellite typing
Less than 1ng of DNA required to type 13-15 loci
Can be processed within 24 hours
Relatively degraded DNA samples can be used
What is the issue with whole genome amplification (WGA)?
As screens become more sensitive the possibility of contamination becomes greater
What is clonal identity?
Small samples of crops are taken and tested in labs to ensure they are what they are being sold as
What is distinctness, uniformity and stability (DUS) testing?
A way of determining whether a newly bred variety differs from existing varieties within the same species (distinctness), whether the characteristics used to establish distinctness are expressed uniformly (uniformity) and that these characteristics do not change over subsequent generations (stability)
Why does DUS testing exist?
So that new varieties can legally gain access to their market via the U.K. National List and the granting of Plant Breeders Rights (intellectual rights)
Where is a DUS test normally conducted?
In the field or glasshouse over two consecutive growing seasons, and over this time a number of mainly morphological characteristics are measured and established.
What is marker-assisted selection (MAS)?
The use of DNA markers that are tightly linked to target loci as a substitute for or to assist genetic screening
What is the assumption made during marker-assisted selection (MAS)?
That DNA markers can reliably predict phenotype
What is the process of marker-assisted selection?
Cross parents with desirable characteristics, screen offspring of F2 generation for even better desirable characteristics e.g. resistance to high salinity, bacterial blight or phosphorus deficiency
Advantages of marker-assisted selection (MAS):
1) Simpler method compared to phenotypic screening
2) Selection at seedling stage
3) Increased reliability
4) More accurate and efficient at selection of specific genotypes
5) More efficient use of resources