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Forensic BioScience > Uses of DNA Profiling > Flashcards

Uses of DNA Profiling Flashcards

1
Q

Uses of DNA Profiling?

A

Forensic casework
Paternity
Identification- mass disasters, no ID on body
Genetic Diseases

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2
Q

What are the methods of DNA profiling?

A

RFLP (Restriction Fragment Length Polymorphisms)
PCR (polymerase chain reaction)->STRs (short tandem repeats)- amplifies specific sections of DNA (3-7 bases), more likely to get results especially with degraded samples
Low Copy Number
Familial Searching- similar profile on DNA database
Y-STR testing- targeting male cells, approx. 200 Y-STR sites on Y chromosome, problem- less variation meaning less discrimination between people
Mitochondrial DNA-link family members, hair sample with no root
DNA Boost- computer programme (2005) helps to separate mixed samples

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3
Q

What is the CODIS system used for?

A

Combined DNA index system (USA)

Use 13 core STR loci

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4
Q

What is the NDNAD used for?

A

National DNA Database UK

Use 10 STR loci and XY- X chromosome 6 bases shorter than Y chromosome (Amelogenin)

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5
Q

What is the percentage of the UK population with their DNA profile on the database?

A

5.2%

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6
Q

What is the percentage of the USA population with their DNA profile on the database?

A

0.5%

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7
Q

What do the labels above peaks represent?

A

The loci being looked ay

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8
Q

Why do peaks differ in size?

A

Number of bases present in DNA

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9
Q

What is the probability that someone would watch random DNA sample at any one site?

A

1/10

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10
Q

What is the probability that someone would watch random DNA sample at any three site?

A

1/1000

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11
Q

What is the probability that someone would watch random DNA sample at all 13 CODIS sites?

A

1 in ten trillion

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12
Q

How does site matching make the match likely to be reliable?

A

World population is 6 billion so very it can’t be anyone else if it’s one in ten trillion

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13
Q

Why do increased sites increase reliability?

A

Increased sites means less likely to match a sample at random

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14
Q

What does exclusion mean?

A

Non-match

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15
Q

What does inclusion mean?

A

Match

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16
Q

Why may there be inconclusive results?

A

May be due to analysis, quantity of DNA (difficult to get a full profile), difference in opinion between two analysts

17
Q

How do you calculate the frequency of two allele locus?

A

Frequency of allele 1, f(1)=p

Frequency of allele 2 f(2)=pxp p2

18
Q

When is low copy number used?

A

Very few cells, international cases

Skin sweat in fingerprints (few cells)

19
Q

Why does LCN take longer?

A

Repeat more cycles because less DNA to start with, issues with sensitivities, may obtain DNA profile that’s not connected to the case

20
Q

What are cold cases?

A

Cases open for a long time but are never solved

21
Q

What is familial searching?

A

Have full DNA profile
No matches on DNA database
Similar DNA within family group
Alternatively- partial profile- try to match

22
Q

What can particular markers indicate?

A

Ethnicity

23
Q

What has DNA technology led to an increase of?

A

Examination of “Cold cases”

24
Q

What are the issues to consider?

A

Contamination
Changes in guidelines- samples weren’t collected as efficiently as they are now
Continuity of evidence i.e. possibility of tampering from collection to storage
Storage of material e.g. microscope slides- may have badly degraded if not properly stored

25
Q

How can DNA evidence be used to identify paternity?

A

Attempting to match alleles of the child, other than those that match the mother

26
Q

What are the rules of inheritance

A
  1. Child has 2 alleles for each autosomal marker (one from mother and one from biological father
  2. Child will have mother’s mitochondrial DNA haplotype (barring mutation)
  3. Child, if a son, will have father’s Y-chromosome haplotype (barring mutation)
27
Q

What are some features that identify a person?

A 
Hair colour
Height
Sex
Weight
Race
Tattoos/piercings/birthmarks
28
Q

What are the guidelines by interpol?

A

Genetic linking of victims to members of natural family
Conclusion victims not related
Matching body parts

29
Q

What are some examples of personal effects?

A

Hairbrushes, toothbrushes

30
Q

What is the use of DNA profiling for genetic diseases?

A

Current standard Forensic DNA tests do not look at genes
Mutations in genes can leads to defects
Genetic diversity-polymorphism
Mutations within restriction sites changes the size of fragments
Detect genetic diseases by RFLP or PCR
e.g. sickle-cell anaemia, cystic fibrosis

31
Q

What is the modern use of Y-STR testing?

A

Matching Y-STR Haplotype used to confirm identities

E.g. Sadaam Hussein- carried out Y-STR testing because he had a number of body doubles

Forensic BioScience (19 decks)

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