Chapter 7 DNA Fingerprinting

Introduction and History of Biological Evidence in Forensics

DNA ______, also known as DNA profiling, is used in criminal or legal cases with a high degree of ______.

Biological evidence such as ______, ______, ______, ______, and ______is examined for the presence of inherited traits.

What examples can you give of how laboratory techniques used in forensics were originally developed for other purposes?

The Function and Structure of DNA

DNA molecules make up ______structures and are found in the ______of cells in the human body.

How would you describe and explain the double helix, twisted-ladder structure of a chromosome?

Can you explain the terms allele, genome, and junk DNA?

DNA Identification

______DNA contains many of the ______of repeated base sequences that identify individuals.

In a human population, these are called ______.

In 1984 a technique was developed for ______and ______these variable areas.

This DNA Fingerprinting appears as a pattern of ______on X-ray film. These patterns can be used for ______of individuals.

The number of ______of the same repeated base sequence in DNA ______among individuals.

Variable Number of Tandem Repeats (_____)

Within junk DNA, ______of DNA are repeated multiple times.

Some can be ______bases in length.

Short Tandem Repeats (____)

Within junk DNA, other ______of DNA also are repeated multiple times.

These usually are only ______bases in length and are becoming the ______sequences for analysis.

DNA Profiling and DNA Population Databases

VNTR and STR data are analyzed for (a) ______matching and (b) ______matching.

______is the study of variation in genes among groups of individuals.

Calculations can be made based on these groups to determine the ______a random person would have the same alternative form of a gene (an allele) as (a) a ______in a crime or (b) an ______in a paternity case.

Sources of DNA

A perpetrator may leave ______evidence, such as saliva or blood, at a crime scene.

This ______evidence is capable of identifying a specific person.

But a small amount of biological evidence might be considered only ______evidence, and it may be consumed during forensic testing.

In 1993, however, the ______(PCR) technique was invented. It generates ______of DNA evidence.

Avoiding contamination in the collection and preservation of DNA

  1. Use disposable ______and collection ______.
  2. Avoid physical ______, ______, ______, and ______in the evidence area.
  3. _____-_____ evidence and put it into new ______bags or envelopes.
  4. If evidence cannot be dried, ______it.
  5. Keep evidence ______and ______during transportation and storage.

Preparing DNA Samples for Fingerprinting

  1. DNA is mixed with special ______.
  2. The enzymes ______the DNA in specific places forming different sized ______.
  3. The DNA is loaded into the chambers found on an ______.
  4. An electric ______is passed through the gel separating the fragments by ______.

Preparing DNA Samples for Fingerprinting--Extraction

  1. ______are isolated from biological evidence such as blood, saliva, urine, semen, and hair.
  2. The cells then are ______to release the DNA from proteins and other cell components.
  3. Once released, the DNA can be ______from the cell nucleus.

Preparing DNA Samples for Fingerprinting

Amplification

With some VNTR analysis, polymerase chain reaction (PCR) can be used to ______the DNA that contains the VNTRs.

In STR profiles, restriction enzymes are ______; PCR allows the amplification of the strands with STR sequences.

Electrophoresis

DNA samples are placed in ______through which electronic ______are passed.

DNA fragments line up in ______along the length of each gel.

Probes

DNA probes are used to identify the ______in a person’s DNA.

Different DNA probes are made up of different ______of DNA bases complimentary to the DNA strand.

The probe binds to ______in the strand (see the fragmentary DNA bands above).

In most criminal cases, 6-8 probes are used.

Analysis of DNA Fingerprints and Applications

Bands and widths are ______in matching samples of DNA.

DNA fingerprinting can (a) match crime scene DNA with a ______, (b) determine maternity, paternity, or match to ______, (c) eliminate a ______, (d) free a ______individual, and (e) identify ______.

...... Summary ......

DNA contains the information needed for ______in a sequence of nitrogenous bases.

DNA analysis allows even a ______of tissue to be identified with a single individual.

DNA contains, in non-coding regions called ______, many repeated sequences that vary in number between individuals.

These differences between individuals can be used to produce a ______for an individual.

______(PCR) for DNA ______has largely eliminated the problem resulting from the ______samples usually available.

DNA evidence must be collected carefully to avoid ______with other DNA.

DNA analysis involves ______, ______, and visualization.

DNA profiles are kept by police agencies in ______databases.