Forensics Mid Term

What is the molecular structure of the DNA molecule?

DNA is a double helix, composed of two complementary single strands held together by hydrogen bonds.

What are the subunits of DNA?

DNA is made up of monomer nucleotides, which consist of a sugar, a phosphate, and a base (A, T, C, or G).

What forms the backbone of the DNA molecule?

The sugar and phosphate components of the nucleotides form the backbone of the DNA molecule.

What is compared in forensic DNA profiling?

Non-coding tandem repeat regions of DNA are compared, not the gene sections.

What are VNTRs and STRs in the context of DNA profiling?

VNTRs (Variable Number Tandem Repeats) are longer repeating sequences, while STRs (Short Tandem Repeats) are shorter sequences.

What does polymorphic mean in DNA profiling?

Polymorphic refers to sections of DNA that have many different forms in the population, allowing differentiation among individuals.

How is a person's DNA type at each locus represented in writing?

It is represented by two numbers separated by a comma (e.g., 14, 22).

How many sites of DNA repeats are compared in a standard forensic profile?

13 sites plus Amelogenin for sex determination.

How is the probability of a random match calculated?

Multiply the frequency of the first repeat number by the frequency of the second repeat number for each site, adjusting for homozygous and heterozygous results accordingly.

Why is it better to compare more loci in forensic work?

It narrows down the group of possible suspects and allows more exclusions based on differing DNA at single sites.

What is the molecular goal of gel electrophoresis?

The goal is to separate pieces of DNA by size.

How does gel electrophoresis work?

Add DNA samples to one end of the gel, apply power, and allow DNA to move through the gel, with smaller pieces moving farther.

What is the function of restriction enzymes in RFLP?

Restriction enzymes cut DNA into fragments for easier analysis in forensic comparison.

What is a DNA probe?

A small piece of radioactive DNA complementary to a repeat section, used to visualize the size of DNA fragments.

What is the purpose of PCR in DNA analysis?

PCR (Polymerase Chain Reaction) is used to copy specific sections of DNA, such as STR regions.

What role do primers play in PCR?

Primers are short sequences that anneal to single-stranded DNA, allowing Taq polymerase to replicate the DNA.

What is CODIS?

CODIS stands for Combined DNA Index System, a federal DNA database from crime scenes and offenders.

How do DNA profiles from a biological parent and child compare?

A child should have one allele in common with each biological parent at every tested locus.

What is the purpose of documenting a crime scene?

Documentation is important for establishing the details of the scene, preserving evidence, and supporting investigations.

What does individualization in forensic evidence ensure?

Individualization ensures near 100% certainty that two samples come from the same source.

What criteria do forensic scientists use to evaluate the reliability of testimonial evidence?

Testimonial evidence is often unreliable due to subjective perceptions and varying interpretations by witnesses.