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Forensic Bio Ch. 11
Hairs and Fibers
| Question | Answer |
|---|---|
| the scale structure covering the exterior of the hair | cuticle |
| the main body of the hair shaft | cortex |
| a cellular column running through the center of the hair | medulla |
| the initial growth phase during which the hair follicle actively produces hair | anagen phase |
| a transition stage between the anagen and telogen phases of hair growth | catagen phase |
| the final growth phase in which hair naturally falls out of the skin | telogen phase |
| a translucent piece of tissue surrounding the hair's shaft near the root; it contains the riches source of DNA associated with hair | follicular tag |
| DNA present within the nucleus of a cell; this form of DNA is inherited from both parents | nuclear DNA |
| DNA present in small structures outside the nucleus of a cell which supply energy to the cell; this form of DNA is inherited maternally | mitochondrial DNA |
| fibers derived entirely from animal or plant sources | natural fibers |
| fibers derived from either natural or synthetic polymers; the fibers are typically made by forcing the polymeric material through the holes of a spinneret | manufactured fibers |
| a molecule with a high molecular mass | macromolecule |
| two or more atoms held together by chemical bonds | molecule |
| the basic unit of structure from which a polymer is constructed | monomer |
| a substance composed of a large number of atoms; these atoms are usually arranged in repeating units or monomers | polymer |
| an appendage of the skin that grows out of the hair follicle | hair |
| can the body area from which a hair originated be determined? | normally, yes |
| can the racial origin of hair be determined | in some instances, yes |
| can the age and sex of an individual be determined from a hair sample | age: no, except for infant hair sex: no |
| is it possible to determine if a hair was forcibly removed from the body? | possibly, by examining the hair root |
| are efforts being made to individualize human hair? | yes, nuclear DNA can be found in hair roots (if present) and mitochondrial DNA can be found in the hair itself |
| is it possible to determine whether hair came from a deceased individual | at times, with certain hair |
| can DNA individualize a human hair | if the DNA is nuclear, yes. If it is mitochondrial, it can distinguish an individual to a maternal line |
| shaft diameter: moderate w/ minimal variation (mean diameter for human hair is 80 um) pigment granules: sparse to moderately dense with fairly even distribution cross-sectional shape: oval | caucasian |
| shaft diameter: moderate to fine w/ considerable variation pigment granules: densely distributed (hair shaft may be opaque) & arranged in prominent clumps shaft: prominent twist and curl cross-sectional shape: flattened | negroid |
| Shaft diameter: coarse and usually with little or no variation Pigment granules: densely distributed and often arranged in large patchy areas or streaks Medulla: prominent (often broad and continuous) Cuticle: thick Cross-sectional shape: round | mongoloid |
| Hair is an appendage of the skin, growing out of an organ known as the _________. | hair follicle |
| The three layers of the hair shaft are the _________, the _________, and the _________. | cuticle, cortex, and medulla |
| The scale pattern of hair’s _________ can be observed by making a cast of its surface in clear nail polish or softened vinyl. | cuticle |
| The _________ contains the pigment granules that impart color to hair. | cortex |
| The diameter of the medulla relative to the diameter of the hair shaft is the _________. | medullary index |
| Human hair generally has a medullary index of less than _________; the hair of most animals has an index of _________ or greater. | one-third; one-half |
| Human head hairs generally exhibit no ___________ | medullae |
| If a medulla exhibits a pattern, the hair is _________ in origin | animal |
| Much of a hair’s resistance and stability is attributed to the _________ | cuticle |
| The three stages of hair growth are the _________, _________, and _________ phases. | anagen, catagen, telogen |
| _________ hairs are short and curly, with wide variation in shaft diameter. | pubic |
| True or False: It is possible to estimate when hair was last bleached or dyed by microscopic examination._________ | true |
| Hair forcibly removed from the body (always, often) has follicular tissue adhering to its root. | often |
| Microscopic hair comparisons must be regarded by police and courts as presumptive in nature, and all positive microscopic hair comparisons must be confirmed by _________ typing. | DNA |
| A(n) _________ hair root is a likely candidate for DNA typing. | anagen |
| The onset of postmortem changes to the root portion of hair is only observed in __________ and ___________ hairs. | anagenic and catagenic |
| A minimum collection of _________ full-length hairs normally ensures a representative sampling of head hair. | 25 |
| A minimum collection of _________ full-length pubic hairs is recommended to cover the range of characteristics present in this region of the body. | 25 |
| The ultimate value of fibers as forensic evidence depends on the ability to narrow their _________ to a limited number of sources or even to a single source | origin |
| The most prevalent natural plant fiber is _________. | cotton |
| __________, such as rayon and acetate, are manufactured by chemically treating cellulose and passing it through a spinneret | regenerated fibers |
| Fibers manufactured solely from synthetic chemicals are classified as _________. | synthetic |
| _________was the first synthetic fiber. | nylon |
| A first step in the forensic examination of fibers is to compare _________and _________ | color and diameter |
| The microspectrophotometer employing _________ light is a convenient way for analysts to compare the colors of fibers through spectral patterns. | visible |
| The microspectrophotometer employing _________ light provides a rapid and reliable method for identifying the generic class of a single fiber. | infrared |
| Normally, fibers possess (individual, class) characteristics. | class |
| If a body is thought to have been wrapped at one time in a blanket or carpet, _________ of exposed body areas may reveal fiber strands. | adhesive tape lifts |
| _________ are composed of a large number of atoms arranged in repeating units. | polymers |
| The basic unit of the polymer is called the _________. | monomer |
| _________ are polymers composed of thousands of amino acids linked in a highly organized arrangement and sequence | proteins |
| Synthetic fibers possess the physical property of _________ because they are crystalline. | birefringence |
| How is the hair cuticle used to identify different animal species? | The hair cuticle, the outer layer of the hair shaft, has unique scale patterns (coronal, spinous, imbricate) that vary between species. Forensic scientists use microscopy and casting methods to examine these patterns to identify different animal species |
| What aspect of the hair cortex is most important for the criminalist and why? | hair cortex contains pigment granules that determine color, shape, & distribution, unique to each individual. Criminalists use microscopy to analyze these features, comparing characteristics like presence of a medulla and identifying dyed or abnormal hair |
| What is the follicular tag and why is it important to forensic scientists studying hair? | The follicular tag, found near the hair root, contains DNA crucial for forensic analysis. It’s a rich DNA source, especially when hair is forcibly removed. DNA typing from the tag helps link hair to individuals, aiding in criminal investigations |
| In comparing two hair samples, what aspects of the hair is the criminalist particularly interested in matching? What other features of hair are important to compare? | Forensic scientists compare hair samples based on color, length, diameter, medulla type, pigment granules, & signs of dye or bleach. also look for abnormalities, infections, or diseases & use a microscope to analyze differences in microscopic features |
| Which of the following can be confidently determined by a microscopic examination of hair: age, sex, racial origin, the part of the body from which the hair came, or whether the hair was pulled out or fell out? | racial origin, part of the body, and whether the hair was pulled out or fell out |
| Why are most hair specimens collected at crime scenes not good sources of DNA? | Most hair at crime scenes isn't a good DNA source due to growth phase (telogen hairs lack DNA), absence of follicular tissue, & the fact most hairs are naturally shed. Forcibly removed hairs are better, but mitochondrial DNA can be used as alternative |
| What type of hair specimens are potentially the richest source of nuclear DNA and why? | The follicular tag, found near the hair root, is the richest source of nuclear DNA, especially in hairs forcibly removed during the anagen phase. Telogen and catagen phase hairs, which are shed naturally, have insufficient DNA for typing |
| List three important considerations when submitting hair samples to a crime laboratory. | When submitting hair samples to a crime lab, include standard/reference samples from both the victim and suspects, collect hairs from the same body area, and ensure a representative sample (25 full-length hairs) to ensure accurate forensic analysis. |
| How has mass production limited the value of fiber evidence? | it reduces the value of fiber evidence by making fibers widely available, limiting the ability to trace them to a specific source. Identical fibers are common, making individual identification difficult and reducing their forensic significance |
| What is the first and most important step in the examination of a fiber? What physical characteristics of fibers might help an examiner identify it? | The first step in fiber examination is a microscopic comparison of color and diameter. Other characteristics like striations, delustering particles, and cross-sectional shape are also examined to help identify fibers and link them to specific sources |
| How can microspectrophotometry and chromatography be used to analyze fiber evidence? | Microspectrophotometry uses light to analyze fiber absorption spectra, revealing color and chemical composition. Chromatography, including GC, HPLC, and TLC, separates and identifies chemical components, helping distinguish fibers based on their makeup. |
| Name two analytical devices used by forensic scientists to determine the class of a fiber. | Forensic scientists use infrared microspectrophotometers & infrared spectrophotometers to analyze fibers. devices help identify fiber classes & subclasses by examining their chemical composition & absorption patterns, aiding accurate forensic comparisons |
| morphological features that could be important in comparing fibers | Lengthwise striations on the surface of the fiber Presence of delustering particles that reduce shine Cross-sectional shape of the fiber microscopic comparisons b/w questioned & standard/reference fibers for color & diameter characteristics |
| ___________ are composed of polymers, | Synthetic fibers |
| _________ fibers are manufactured. | Man-made |
| rayon, acetate, and triacetate are examples of what type of fiber | regenerated fibers |
| nylons, polyesters, and acrylics are examples of what type of fiber | synthetic fibers |
| ___________ are produced solely from synthetic chemicals | Synthetic fibers |
| ____________ are manufactured from natural raw materials | Regenerated fibers |
| Wool, Mohair, Cashmere, Furs, and Cotton are examples of what type of fiber | natural fibers |
| ___________ are derived in whole from animal or plant sources. | Natural fibers |
| What part of the hair shaft is most resistant to chemical decomposition? | cuticle |
| what was the first man-made fiber | rayon |
| what is the rate of human hair growth per month? | 1 cm |
| cellulose is the basic component of ______ | wood |
| the portion of the hair containing its scales | cuticle |
Created by:
hbhull05