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CHY183 > Lecture 15: DNA > Flashcards

Lecture 15: DNA Flashcards

1
Q

What is the length of repeat units on chromosome 1?

A

16 bp

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2
Q

How many different alleles can exist for the repeat units on chromosome 1?

A

27

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3
Q

Why is PCR technology not suitable for RFLP DNA typing?

A

RFLP strands are too long, often numbering in the thousands of bases

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4
Q

What technology is best for DNA strands under a couple of hundred bases?

A

PCR

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5
Q

What is the latest method of DNA typing that emerged as the most successful?

A

Short Tandem Repeat (STR) analysis

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6
Q

What is the length of short tandem repeats (STR) on the chromosome?

A

Less than 450 bases

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7
Q

Why are STRs ideal candidates for amplification by PCR?

A

Due to their shortness and overcoming limited-sample size problem

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8
Q

How much DNA is required for STR analysis, often equivalent to 18 DNA containing cells?

A

As little as 125 picograms of DNA

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9
Q

What is the advantage of STRs over RFLP in terms of susceptibility to
degradation?

A

STRs are much less susceptible to degradation

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10
Q

How can one determine the number of repeats of a specific sequence in an
STR?

A

By examining the distance the STR has migrated on an electrophoretic plate

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11
Q

Why are STRs highly attractive to forensic scientists?

A

Due to the hundreds of different STRs found in the human genome

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12
Q

What is the concept of multiplexing in relation to STR analysis?

A

Simultaneously extracting and amplifying a combination of different STRs

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13
Q

What does capillary electrophoresis use instead of flat gels for separation?

A

Thin tubes

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14
Q

What rule allows for a high degree of discrimination by analyzing a
combination of STRs?

A

Product Rule

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15
Q

How is the probability of having a particular combination of STR alleles
calculated?

A

By the product of their frequency of occurrence in a population

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16
Q

How many standard STRs have U.S. crime laboratories standardized on for
entry?

A

13

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17
Q

What are primers in DNA replication?

A

Short strands of DNA used to target specific regions for replication

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18
Q

How are DNA fragments sorted in RFLP analysis?

A

By cutting DNA with restriction enzymes and separating fragments by electrophoresis.

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19
Q

Describe the role of restriction enzymes in RFLP.

A

They act as specialized scissors, cutting DNA at specific base sequences.

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20
Q

What is the purpose of Southern blotting in RFLP?

A

To transfer DNA fragments to a nylon membrane for visualization.

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21
Q

Explain how DNA can be characterized using electrophoresis.

A

DNA fragments are separated by size and mobility in a gel matrix

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22
Q

What is the key principle behind DNA typing using RFLP?

A

Variations in repeated sequences and lengths of DNA fragments

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23
Q

What are tandem repeats in DNA?

A

Portions of DNA with repeated sequences of bases, like microsatellites and minisatellites.

24
Q

How are RFLPs visualized in DNA fingerprinting?

A

By treating a nylon sheet with radioactive probes and exposing it to X-ray film.

25
Q

What is the function of DNA polymerase in DNA replication?

A

To rebuild each of the strands by adding free nucleotides.

26
Q

How can the differences in DNA length be detected in RFLP?

A

By cutting DNA with restriction enzymes and analyzing fragment sizes.

27
Q

What is CODIS and who developed it?

A

CODIS is a DNA database system developed by the FBI

28
Q

What types of DNA profiles are stored in CODIS?

A

DNA profiles from convicted offenders, unsolved crime evidence, and missing persons.

29
Q

How many profiles does CODIS currently contain?

A

How many profiles does CODIS currently contain?

30
Q

List at least 3 uses of DNA forensics mentioned in the notes

A

Link suspects with crime scenes, identify unknown victims, and establish paternity.

31
Q

What are common sources of DNA evidence at crime scenes?

A

Blood, semen, saliva, urine, skin cells, hair, bone, teeth.

32
Q

How should dried blood on a surface be collected?

A

Dried blood should be removed using a sterile cotton swab lightly moistened with distilled
water.

33
Q

What precautions should be taken when handling biological evidence?

A

Wear disposable gloves, face mask, lab coat, eye protection, and shoe covers

34
Q

Why should biological evidence not be packaged in plastic containers?

A

Residual moisture in plastic containers can contribute to the growth of DNA-destroying bacteria

35
Q

What is CODIS used for

A

CODIS is used as a national DNA database.

36
Q

Describe the characteristics of Unlinked loci.

A

Unlinked loci are independently inherited and have no physical characteristics

37
Q

What is the significance of the amelogenin gene in Sex Determination by STRs?

A

The amelogenin gene helps determine the sex of an individual by showing different band
patterns.

38
Q

How is sex determined using the amelogenin gene?

A

Males show two bands, while females show one band.

39
Q

Explain Y-STR analysis and its purpose.

A

Y-STR analysis focuses on markers located on the Y chromosome, useful for male
identification and family relationships.

40
Q

What key advantage does Y-STR analysis offer over conventional STR
analysis?

A

Y-STR analysis has simpler results, with a single band instead of two bands.

41
Q

How does DNA Fingerprinting help in criminal investigations?

A

DNA Fingerprinting can link suspects to evidence or victims through DNA profiles.

42
Q

What type of DNA is used for individual characterization apart from nuclear
DNA?

A

Mitochondrial DNA is used, inherited maternally and located outside the nucleus

43
Q

Explain the difference between Mitochondrial DNA and Nuclear DNA.

A

Mitochondrial DNA is maternal and outside the nucleus, while nuclear DNA is from both
parents and inside the nucleus.

44
Q

What is the role of mtDNA in forensic analysis

A

Mitochondrial DNA is used for samples where STR analysis may not be possible.

45
Q

What type of forceps should be used for picking up items of evidence?

A

Disposable forceps

46
Q

How should evidence such as cigarette butts be handled during collection?

A

With clean forceps

47
Q

Why is it recommended to use disposable forceps for evidence collection?

A

So they can be discarded after single use

48
Q

How should each item of evidence be stored?

A

In its own well-ventilated container

49
Q

What percentage of the human genome encodes proteins?

A

5%

50
Q

Define DNA polymerase.

A

An enzyme that assembles new DNA strands during replication.

51
Q

Explain the structure of a nucleotide.

A

Comprised of a sugar, a phosphate group, and a base

52
Q

What is the function of DNA in directing protein production?

A

Determines the sequence of amino acids in a protein

53
Q

Describe the complementary base pairing in DNA.

A

Adenine pairs with thymine; guanine pairs with cytosine.

54
Q

What is the role of polymerase chain reaction (PCR) in DNA testing?

A

Replicate small amounts of DNA for analysis.

55
Q

What is the significance of primers in PCR?

A

Short DNA strands used to target specific regions for replication.

56
Q

Explain the process of DNA replication

A

Involves unwinding DNA, adding free nucleotides, and polymerase synthesizing new strands.

CHY183 (17 decks)

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