Extra information

Question 1

Tell me about the Pseudoautosomal region, PAR region

Answer 1

• It is homologous sequences on the x and y chromosome
• The PAR behaves like autosome and recombines during meiosis thus meaning it is inherited autosomally rather than in a sex linked fashion

Question 2

Tell me about Amelogenin

Answer 2

• A group of protein isoforms produced by alternative splicing or proteolysis from AMELX gene, on X chromosome, or AMELY on Y chromosome
• It allows for sex identification as AMELX intron 1 has a 6bp deletion relative to intron 1 of AMELY and this can be detected by PCR followed by electrophoresis

Question 3

Tell me the history of DNA profiling and the different methodologies used

Answer 3

• DNA STR profiling first used in 1994 by the FSS which used 4 STR loci but this wasnt very discriminating
• 1995 Second generation multiplex (SGM) was introduced which was based on** 6 STR loci and amelogenin**
• 1995 NDNAD also used
• 1996 The profiles of biological materials analysed from crime scenes was uploaded
• 1999 SGMPlus which used 10 loci was introduced to reduce chance of getting adventitious match between individuals
• 2014 DNA17 was used which uses 16 STR loci (10 from SGMPlus and 6 new ones) and amelogenin

Question 4

Tell me about the SRY region and why the Y chromosome has shrunk?

Answer 4

The SRY region is the sex determination region of the y chromosome
To keep the SRY region from getting ‘fixed’, the Y chromosome stopped recombinating with most of the X chromosome which led to the Y chromosome size shrinkage

Question 5

What is meant by a founder effect?

Answer 5

The loss of genetic variation that occurs when a new population is established by a small number of people from a large population

Question 6

Whats the bottleneck effect?

Answer 6

A sharp reduction in population size due to environmental effects e.g., famine, earthquakes or human activities e.g., international culling, violence

Question 7

How do you calculate the degrees of freedom for the HWE?

Answer 7

d.f.=number of genotypes - number of alleles

Question 8

After DNA amplification via PCR, capillary electrophoresis is carried out. What is the master mix for CE made up of?

Answer 8

1. Formamide to stop the strands annealing again
2. GS_600LIZ size standard dye

Question 9

Tell me about MtDNA and its forensic applications

Answer 9

• The section of human DNA in the mitochondrial genome is known as the mitochondrial hypervariable region -1 (HV-1)
• This area is highly polymorphic and DNA sequencing offers the best methods to characterise DNA
• In a forensic application the HV-1 DNA sequences can be analysed and compared
• MtDNA is very useful for highly degraded samples which contain little autosomal DNA
• More recently, some methodologies have began sequencing the entire hypervariable region; HV-1, HV-2 and HV-3

Question 10

What is one of the assumptions of Mendelian inheritance?

Answer 10

50% of genetics from mother and 50% for father
(HWE assumption)

Question 11

What is the Hypervariable region of the mitochondria?

Answer 11

A hypervariable region (HVR) is a location within nuclear DNA or the D-loop of mitochondrial DNA in which base pairs of nucleotides repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA)

Question 12

What is IrisPlex?

Answer 12

A set of 6 SNPs that have been developed to predict eye colour from DNA sample

The SNPs associated with genes involved in various aspects of human pigmentation, however most in introns and have no causal effect

Question 13

What blotting technique is used in DNA fingerprinting after electrophoresis

Answer 13

Southern blot analysis is a laboratory method used to study DNA. Specifically, purified DNA from a biological sample (such as blood or tissue) is digested with a restriction enzyme(s), and the resulting DNA fragments are separated by using an electric current to move them through a sieve-like gel or matrix, which allows smaller fragments move faster than larger fragments. The DNA fragments are transferred out of the gel or matrix onto a solid membrane, which is then exposed to a DNA probe labeled with a radioactive, fluorescent or chemical tag. The tag allows any DNA fragments containing complementary sequences with the DNA probe sequence to be visualized within the Southern blot. The method is named for its creator, British molecular biologist Edwin Southern.

Question 14

What act came in for the NDNAD in 2013?

Answer 14

The Protection of Freedom Act 2013 ensured that 1,766,000 DNA profiles taken from innocent adults and children were deleted from the UK National DNA Database.

Question 15

When may SNPs be more useful that STRs?

Answer 15

When DNA is degraded as have less bp available

Question 16

What are the different conditions for STR typing on capillary electrophoresis, what is each one

Answer 16

1. Sizing precision: Need to ensure that between runs sizing is consistant so alleles can be called properly
2. Spectral resolution: Need to separate different flourescent dye colours, name the common dyes (FAM, PET, VIC, NED, LIZ)
3. Spatial separation: Need to be able to separate alleles that differ in size by a single nucleotide, one dye allocated size standard e.g., Liz, the alleles need to be distinguishable by 1bp so sometimes** primer design or mobility modifiers** can be used, uses polyacrylamide gel electrophoresis (describe how this works)

Question 17

How are SNPs involved with DNA variation?

Answer 17

SNP –> Mutation –> DNA variation
ie.,
1.** Phenotyping- pigmentation: **SNPs involved in melanin variation, development of DNA phenyotyping (VNTRs –> STRs–> SNPs)
2. Facial feature predictions: based on 24 SNPs
3. Genealogy: Y-DNA, MtDNA and autosomal DNA testing
4. Metagenomics: Study of the structure and function of entire nucleotide sequence of organisms