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DNA Quiz 1
| Question | Answer |
|---|---|
| Plasma - fluid portion of blood makes up | 55% of blood volume |
| Red, white blood cells and platelets are | solid components suspended in plasma |
| blood types are determined by | presence or absence of antigen residing on surface of red blood cell |
| 4 blood types | A, B, AB, O |
| the Rh factor - a protein - can be either present (+) or absent (–). | This results in the eight most common blood types: A+, A-, B+, B-, O+, O-, AB+, and AB-. |
| Approximately 43% of the population is | type O |
| 42% is | type A |
| 12% is | type B |
| 3% is | type AB |
| universal donor type is | o negative |
| type o positive can donate to | any positive type A+, B+, O+, AB+ |
| CODIS | Combined DNA Index System |
| FBI introduced CODIS to USA in | 1998 |
| USA CODIS categories | Convicted offenders • Arrestees • Forensic index (crime scenes) • Missing persons • Unidentified humans • Biological relatives of missing persons |
| CODIS implemented in Canada in | 2000 |
| Canada's version of CODIS is | NDDB National DNA Data Bank |
| CODIS in Canada managed by | RCMP |
| NDDB categories are | Convicted Offenders Index • Crime Scene Index • Victims Index • Missing Persons Index • Voluntary Donors Index • Relatives of Missing Persons Index • Human Remains Index |
| Purpose and Use of CODIS | is to generate investigative leads when biological evidence is recovered from crime scenes. |
| If a match is found, law enforcement agencies from multiple jurisdictions can | coordinate their investigations and share independently developed leads. |
| This match can then be used by law enforcement to | obtain a court order (DNA warrant) authorizing the collection of a known biological sample from the suspect or offender. |
| Ontario's Centre of Forensic Sciences (CFS) maintains its own | local provincial database to support investigations across the province. |
| rapid DNA results | cannot be uploaded to NDDB |
| key characteristics of DNA | genetic building block - found in all living things including some viruses structure - double helix location - Virtually every cell contains DNA. Nuclear DNA is housed in the nuclei of cells |
| Four bases associated with DNA: | adenine (A), cytosine (C), guanine (G), and thymine (T) |
| Complimentary base pairing: | G always pairs with C and A always pairs with T |
| The average human chromosome has DNA containing | 100 million base pairs DNA |
| A nucleotide is a composed of | a sugar molecule, a phosphorous-containing group, and a nitrogen-containing molecule called a base |
| What is DNA Profiling | A scientific technique used to identify individuals based on their unique DNA sequence (also called DNA fingerprinting) |
| Development by Sir Alec Jeffreys | Identified variable regions in DNA called "mini-satellites," which differ between individuals. • Enabled the comparison of DNA samples with high accuracy. • The breakthrough took place at the University of Leicester, UK in 1985 |
| Significance of the Discovery | Provided a powerful tool for forensic science and criminal investigations. • DNA profiling could establish biological relationships and match suspects to evidence. |
| Early Applications | Used to prove guilt in criminal cases, Exonerated innocent ppl built public trust in forensic science, closed cold cases, Allowed for paternity testing to confirm familial relationships when there was doubt |
| Impact on Forensic Science | Late 1980s: DNA replaced blood typing for blood evidence analysis • Early 1990s: DNA testing became a more reliable and accurate identification method |
| Impact on Forensic Science | DNA profiling set a new standard for evidence analysis. • Provided a much higher degree of certainty • It highlighted the role of science in improving justice and solving cold cases |
| biological hazards | Blood • Saliva • Seminal fluid • Vaginal secretions • Urine • Feces |
| purpose of ppe | protect yourself from hazards at the scene and protect the scene from contamination |
| evidence collection | DNA is vulnerable to environmental contamination, must refrain from eating, drinking, smoking, littering etc Evidence should only be moved if it is at risk of being lost or destroyed. keep accurate unbroken chain of custody for all DNA materials |
| Collection of Blood Evidence Priority #1: | Personal Protective Equipment (PPE). • At minimum: Mask Gloves |
| The following information should be documented along with the date and time of the observation: | • Size of the stain • Shape of the stain • Location of the stain • Distribution of the stain(s) |
| If the stained object is transportable, | collect the entire item |
| Swabbing: | Use a sterile cotton swab. If sample is dry, moisten the swab with distilled water • Place the swab in a drying cabinet, or use a breathable drying envelope or cardboard box • Package the swab in a box and ensure it is properly labeled and sealed |
| Humans produce | 1–1.3 liters of saliva per day |
| Testing for Saliva: | • No specific test exists • Presumptive tests detect amylase, an enzyme found in saliva, perspiration, semen, vaginal secretions, and breast milk |
| Amylase: | • A digestive enzyme secreted by the pancreas and salivary glands • Found in saliva at 50x higher concentrations compared to other tissues |
| Visual and Fluorescence Properties: | • Saliva stains are not typically visible to the naked eye • Under ALS (Alternative Light Source), saliva fluoresces at the same wavelength as semen but less brightly |
| Collection of Saliva: | • Use a sterile cotton swab to collect saliva from surfaces • Allow samples to dry before final packaging to avoid contamination or mold growth • Store in a dry, cool environment and label clearly |
| in 1935, Waldemar Kutscher and Hajo Wolbergs identified that human semen contains uniquely high levels of | acid phosphatase AP |
| What is Acid Phosphatase? | • An enzyme produced by the prostate gland • Present in both humans and animals |
| Fluorescence Properties: | • Seminal fluid contains flavin, which causes it to fluoresce under ultraviolet (UV) light • Fluoresces blue in the UV range (300–450 nm) • UV light is often used to locate semen stains in forensic investigations |
| Collection of Semen: | under UV light can locate stains • Collect samples using a moistened sterile cotton swab • Allow samples to dry before final packaging to avoid contamination or mold growth • Avoid folding or compressing fabric with stains to prevent smearing |
| urine Detection: | • Identification of urine is rare but can be valuable in investigations • Often associated with cases of strangulation, as victims may involuntarily excrete urine prior to death |
| Testing for Urine: | • Presumptive tests detect creatine, found in high concentrations in urine. • Tests are conducted exclusively in laboratory settings • There is no confirmatory test regularly or specifically used for urine identification |
| Collection of Urine: | sterile cotton swabs or absorbent paper to collect samples from surfaces or fabrics, Allow samples to dry before final packaging Package in paper bags (not plastic) or box to prevent bacterial growth, Store in a dry, cool environment and label clearly |
| No widely used confirmatory test exists for | vaginal secretions |
| Alternative Light Source (ALS) Exams for vaginal secretions: | may fluoresce under ALS, UV or blue light • ALS can help locate biological evidence on clothing, bedding etc when stains are not visible. |
| collection of vaginal secretions | Use sterile cotton swabs • Allow samples to dry before final packaging • Package in paper evidence bags (not plastic) or a cardboard box to prevent bacterial growth • Store in a dry, cool environment and label clearly |
| Penile swabs may be collected from an accused person in specific, limited circumstances | • The process is governed by case law that outlines legal limitations and requirements • Each police service has strict protocols and policies regulating the collection of penile swabs to ensure legal compliance and integrity |
| Infrared (IR) cameras are increasingly being used in forensic investigations | to enhance the detection of blood at crime scenes |
| Non-Invasive Detection: | IR cameras provide a non-destructive method for searching for blood, allowing investigators to preserve the integrity of the scene while gathering evidence. |
| Improved Sensitivity: | IR technology can detect faint traces of blood that may not be visible using traditional methods like luminol or UV light, making it a useful tool in locating hidden or cleaned-up blood stains. |
| Versatility in Various Conditions: | Whether in dimly lit spaces or on surfaces with little contrast, IR cameras can enhance visibility and improve the accuracy of blood detection across different environmental condition |
| Presumptive test | • Preliminary identification • Strong possibility of blood + Highly sensitive + Minimal to no risk of false negatives + Quick, easy and inexpensive + Requires minimal equipment + Field tests – Risk of false positives – Not human specific |
| Confirmatory Tests | • Positive identification • Conclusive presence of blood + Minimal to no risk of false positives + Human specific – Expensive and time consuming – Sophisticated equipment/lab |
| Phenolphthalein | This is a non-destructive test so DNA analysis can still be done after. |
| The kit contains 3 solutions to be applied in sequence | Solution A is phenolphthalin, a colorless reduced form of phenolphthalein. Solution B is phenolphthalein, a colorless chemical that turns pink in the presence of blood when oxidized by hydrogen peroxide. Solution C is 3% hydrogen peroxide |
| An immediate fuchsia-pink colour change indicates a | presumptive positive for blood. |
| Hemastix | the unknown sample is collected and directly applied to the reagent strip. An immediate dark green colour change indicates a presumptive positive for blood. |
| Hexagon OBTI | antibody test, can detect human from animal except primates, weasels and badgers therefore is presumptive and needs further confirmation |
Created by:
skyep25