STRs

What is antigen polymorphism? What are the forensic applications?

Means there's different locations on the gene with many different allele types for antigens. Most commonly used in blood typing

Who invented the first form of DNA polymorphism?

Sir Alec Jeffrey

What was the technique created by Jeffrey?

Used varaible near tandem repeats to solve a UK murder case in 1986

How much DNA do humans differ in?

0.3%

Where do we find most of the variation in human dna? Why?

Most variation is in the length of noncoding regions. These can have variation without harming the individual

How are repeats classified?

Length and number of repeat unit. Overall length of repeat region.

What is a long repeat? Where are they typicall found?

100s to 1000s bps. Found around centromere

What are mini-satellite repeats? What are they used in?

10s to 100 bps. Used in PCR

What are micro-satellite repeats?

STR and simple sequence repeats. 2-7 bp. Most commonly used in forensics

How many sets of STRs should an individual have?

Two sets which can vary in length of repeats

Explain how the primer sequence for STRs work.

Primer sequences are the same for everyone since only the length changes, not the flanking sequences

What are allele numbers?

Show the amount of repeats at a marker

What is the amplicon number?

Total number of basepairs from primer to primer

What types of STRs are NOT used for forensic analysis?

Dinucleotides

What is the most common type of nucleotide used for forensic analysis?

Tetranucleotides

What is the differnce between a simple and compound repeat?

Simple repeat is the same sequence repeated again while compound repeats are two or more adjacent repeats

What is a complex repeat?

Several repeat blocks of variable length with intervening sequences

What are features that are considered good for forensic STRs?

Loci should be far apart or on different chromosomes. Should be able to multiplex. Aim for less than 400 bp.

Describe the first generation multiplex

4 loci. chances of two nonrelated people matching was 1 in 10,000

What is the second generation multiplex?

6 loci. 1 in 5 million chances of random matching. AKA FSS

What is the first commercial kit? How many loci did it include?

Promega CTT triplex. 1 in 500 chances of matching

Originally, how many loci was required for CODIS?

13

What was the European standard set framed around?

Second generation FSS

Why did the Us expand the loci requirements? What was it expanded to?

9 million profiles in the database, began to search for new loci to decrease risk of random matches and improve international compatability. 20 Loci in total.

What is an allelic ladder? How is it made?

Made by combining DNA or PCR amplifications of several people in order to represent the common allele types for a loci. Then, it acts as a reference size to compare the unknowns.

What is a mobility modifier?

Shifts the size of basepair products without the need for creating new primers

If a person's loci has one peak, what would that suggest?

homozygous

What are types of lineage markers?

Mtdna and y chromosome

Why are Y-strs considered supplemental?

Since all strs would be on the same chromosome, they don't hold the same statistical power

What is euchromatin?

Contains functional genes

What is heterochromatin?

noncoding genes

What are pseudoautosomal regions?

5% of the Y chromosome. Only part of y chromosome that can undergo recombination in meiosis

What is the average number of Y-str loci in commerical kits?

23-27

True or false: is there a required y-str marker in CODIS?

False

What is the minimal haplotype loci?

8 common loci that must be included in commercial Y-str kits

What is a A/B bilocal loci?

Occurs when entire sequence is duplicated somewhere else ont he sequence. Alleles are similar in size and you can't tell which is from which section of the chromosome.

What is a I/II bilocal loci?

Occurs when the forward primer binds to the target but also a different location. II will be much larger and most are treated as separate loci

What was the first company to create a commercial kit for Y-STR testing?

Reliagene

What are the three most common results from Y-STR testing?

Exclusion, inconclusive, failure to include

What are rapidly mutating Loci? Why are they useful in forensics?

Particular loci on the y chromosome that can mutate in a single generation.