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Forensics > DNA- Technology > Flashcards

DNA- Technology Flashcards

1
Q

Who first discovered DNA profiling

A

Alex Jeffreys

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2
Q

When was DNA profiling discovered?

A

1984

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3
Q

What was the first application of DNA profiling?

A

The conviction of Colin Pitchfork

Who murdered and raped a girl

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4
Q

What is DNA?

A

Unique and hereditary material
(Except identical twins)
Made up of nucleotides- phosphate, sugar, base (CAGT)
The bases make up a genetic code- produces proteins

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5
Q

What is unique about mitochondrial DNA?

A

It comes from the mother

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6
Q

What are the possible sources of DNA?

A

Saliva, hair root, cells, blood, semen, urine, tissues, bones, teeth

We hope for a trail, i.e. Fingerprints, weapons and bite marks

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7
Q

How much blood to you need to obtain a DNA profile?

A

Only a small quantity

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8
Q

What is the RFLP method to obtain a DNA profile?

A

Restriction fragment length polymorphism
Requires large amounts of DNA, UNDEGRADED-so unlikely in warm conditions
Look for variable number tandem repeats

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9
Q

How does PCR obtain a DNA profile?

A

Polymerase chain reaction
Requires less DNA that can be partially degraded
Short tandem repeats (1-5 bases, repeated 17 times) analysed

However more sensitive to contamination

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10
Q

How does RFLP occur?

A

Variable number tandem repeats
Patterns match
Restriction enzymes cut at points of DNA
Separated by gel electrophoresis

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11
Q

How does PCR occur?

A

Short tandem repeats are copied in many cycles with different temperature changes
95 degrees- DNA separates
Lower temp- primers anneal/bind
72 degrees- taq polymerase synthesises new DNA strand

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12
Q

Why is PCR beneficial?

A

It can make lots of copies of specific sections of DNA

it can analyse degraded samples of DNA as it makes so many copies

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13
Q

What is done after PCR makes the copies of STRs?

A

Analyse it through gel electrophoresis
Primers are labelled with fluorescence
Products exposed to laser bear a

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14
Q

What happens in gel electrophoresis?

A

Smaller sections of DNA travel further through the gel

Thicker bands- same number of repeats for each allele (one from mum one from dad)

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15
Q

What are short tandem repeats?

A

STR’s

People vary in the number of repeats at STR locus

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16
Q

What are the two DNA profiling methodologies?

A

RFLP (restriction fragment length polymorphism)

PCR (polymerase chain reaction)

17
Q

What is the normal appearance of peaks from a DNA profile?

A

They are coloured because they have a fluorescent molecule attached to them during PCR

18
Q

What are stutter bars?

A

DNA repeats slipping out of register during PCR
Usually only 1 repeat length smaller than the main band
Insertion caused by backward slippage
Deletion caused by forward slippage

19
Q

What is LCN?

A

Low copy number
Copy 10 informative sites from smaller amounts of starting material
Takes longer as number of cycles has to increase

20
Q

What is the use of partial profiles?

A

Used for familial searching (on data base)

Can use lcn profiling

21
Q

What is SNP?

A

Single nucleotide polymorphism

22
Q

What is single nucleotide polymorphism?

A 
Difference in a single base unit
Covers 90% of genetic variation
Happens during meiosis
SNP ever 300 base pairs
Helps with phenotyping
23
Q

What is the use of the Y chromosome in STR testing?

A

The amelogenin locus (involved in mineralisation of enamel in developing teeth) is 6 bases shorter in the X chromosome than the Y
One peak on X, 2 on Y

24
Q

What is mitochondrial DNA?

A

1 mitochondrial has 5-10 identical circular molecules of DNA

25
Q

Why is mitochondrial DNA useful?

A

It is useful in mass disasters to link family members as the mitochondrial DNA is only inherited from the mother

26
Q

Why is DNA profiling important?

A

Forensic case work
Identity
Paternity tests
Genetic diseases

Forensics (11 decks)

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