forensics

Define DNA in your own words and explain its primary function in living organisms.

DNA (Deoxyribonucleic Acid) is the molecule that stores genetic information and provides instructions for building proteins and controlling cell activities.

Describe the overall structure of DNA.

DNA is a double helix made of two complementary strands. This structure allows DNA to replicate accurately and protects genetic information.

Explain how the nitrogenous bases are always paired.

A pairs with T, and C pairs with G. This ensures that each new DNA molecule is an exact copy during replication.

Differentiate between a gene, a chromosome, and a genome.

Gene: A specific segment of DNA that codes for a trait.

Chromosome: A tightly coiled structure of DNA containing many genes.

Genome: All the DNA in an organism.

In our DNA labs, what was the purpose of adding a detergent buffer, then adding ethanol?

Detergent is used to break the lipid cell membrane, ethanol is used to pull the dna into strands, and float to surface.

Trace the path of DNA from the entire organism down to a single gene. Use correct biological terms.

Organism → Cell → Nucleus → Chromosome → Gene → DNA sequence

Explain why red blood cells do not contain DNA and discuss how this affects forensic investigations.

Mature red blood cells lose their nucleus to carry more oxygen, making them useless for DNA profiling.

Compare nuclear DNA and mitochondrial DNA Location

Found in Nucleus

Found in Mitochondria- outside nucleus

Compare nuclear DNA and mitochondrial DNA Inheritance

From Both parents

Mother only

Compare nuclear DNA and mitochondrial DNA Forensic usefulness

Individual ID

Degraded samples can be tested

What is DNA typing and why is it such a powerful tool in forensic science?

DNA typing compares genetic patterns to identify individuals.

Describe the three main DNA typing methods and explain when each would be used.

RFLP - old, requires large samples

PCR - copies DNA

STR - modern forensic standard

Why is RFLP considered outdated, and not used as much compared to modern DNA typing methods?

Needs large, high-quality samples and is slow.

Explain how PCR has revolutionized forensic investigations.

Makes millions of copies of small DNA samples, in order to make a more complete picture of the DNA sample.

What are STRs and why are they ideal for identifying individuals?

Short Tandem Repeats are repeating DNA sequences that vary among individuals. Although we share almost the same DNA code, these are different for all individuals.

Why does analyzing more STR loci increase the reliability of DNA matches?

More loci drastically reduce chance of coincidental matches, and ensure positive matches.

Explain the difference between a match, partial match, and exclusion in DNA testing.

Match: Same person Inconclusive: Not enough evidence to make a match

Exclusion: Different individuals

In what situations might a partial match occur, and what could it suggest?

Family members or degraded samples.

Why might mitochondrial DNA be used instead of nuclear DNA in certain cases?

Old bones, hair shafts, burned remains. No tissue available for nuclear testing.

Discuss one ethical concern related to DNA databases such as CODIS.

Privacy, misuse of genetic data, racial bias, surveillance concerns

A crime scene sample is old, degraded, and very small. Which DNA typing method should be used and why?

PCR + STR because they work with small DNA amounts.

A suspect claims DNA evidence is unreliable because humans share 99.9% of their DNA. How would you scientifically respond to this claim?

STRs focus on the variable 0.1%, which is enough to uniquely identify individuals.

Bruce McArthur

serial murders of 8 gay men, bodies concealed in planters at properties he worked at as a landscaper, caught on surveillance footage after they discovered the remains, sentence to life imprisonment with no possibility of parole

The Golden State Killer

13 murders, 50+ rapes, 120+ burglaries in california, solved by using genetic genealogy by uploading dna to public ancestry data base, connected to family tree of a former police officer, found guilty on 13 counts of murder and other crimes

M-25 Rapist

drugged an raped dozens of women working as a london taxi driver, laced alcohol with sedatives, operated around m25 motorway, solved through similar methods, cctv footage, taxi records, and victim accounts, life sentence