Chapter 4: Sources of Biological Evidence

Blood Evidence

One of the most common types of biological evidence that is found at crime scenes.

Plasma

The fluid portion of blood; a subcompartment of extracellular fluid, which is the bodily fluid outside cells.

Erythrocytes, Leucocytes and Platelets

The cellular portion of the blood consists of:

Transcellular fluids

These fluids are considered to be a subcompartment of the extracellular fluid that is contained within epithelial-lined extracellular spaces.

extracellular nucleic acids

Blood plasma and other various bodily fluids usually contain small amounts of nucleic acids known as ________.

Circulating Nucleic Acids

The nucleic acids circulating in plasma.

Cell-Free Nucleic Acids

The nucleic acids that are found in other body fluids, such as saliva and urine.

Extracellular Vesicles (EVs)

The potential sources of extracellular nucleic acids.

Exosomes

____ are one potential source of extracellular nucleic acids.

multivesicular bodies (MVBs)

Exosomes are derived from ______, which are intracellular organelles of the endocytic pathway.

Microvesicles

Shed from the plasma membrane and thus carry along the membrane and cytosolic materials including nucleic acids.

Apoptotic bodies

Are a special type of microvesicle that is formed in apoptotic cells.

plasma membranes

All cells have membranes, also known as ____, which constitute their outer boundaries.

Cell Membranes

A phospholipid bilayer containing lipids, proteins, and carbohydrates.

Membrane proteins

Act enzymes, receptors, or ion channels.

Nucleus

It is surrounded by a nuclear envelope and contains chromosomes and a nucleolus.

**Nucleolus**

A dense, non-membrane-bound structure due to its high RNA content.

**Nucleolus**

Its function is to transcribe ribosomal RNA and to form ribosomes.

gametes

Spermatozoa and ova, which are formed by germ cells, are called ___.

22 autosomes

In humans, each gamete is haploid, containing _______ plus one *sex chromosome.*

**diploid**

Most somatic cells are **______**. It means that they have two copies of each autosome plus two sex chromosomes, XX for females or XY for males.

Homologous Chromosomes

The two chromosomes of a pair in a diploid cell.

nulliploid

Some differentiated cells such as red blood cells and platelets have no nuclei and are designated _____.

Polyploid

Cells that have more than two sets of chromosomes as a result of DNA replication without cell division.

nuclear chromosomes

The _____ of humans consist of complexes of DNA, histone proteins, and nonhistone chromosomal proteins.

chromatin fibers

The large amounts of DNA present in the human chromosome are compacted by their association with histones into nucleosomes and even further compacted by higher levels of folding of the nucleosomes into ____.

protein scaffold

Each chromosome contains a large number of looped domains of chromatin fibers attached to a ______.

chromatin

During the metaphase of mitosis and meiosis of the cell cycle, _____ is the most condensed.

Euchromatin regions

Are areas of chromosomes that undergo normal chromosome condensation and decondensation during the cell cycle.

Heterochromatin

Comprises the chromosomal regions that usually remain condensed throughout the cell cycle.

Centromeres

Are the DNA sequences that are found near the points of attachment of mitotic or meiotic spindle fibers.

Telomeres

The ends of the chromosome; they help stabilize the chromosome and play a role in the replication of DNA in the chromosome.

Cytogenetic Mapping

Each chromosome arm is divided into regions based on the cytogenic bands.

Chromosomes

_____ can be identified on the basis of the size and the positions of the centromeres and cytogenetic banding patterns.

Karyotype

The chromosome constitution.

Karyogram

Includes total number of chromosomes and the sex chromosome composition.

cytosol fluid

The cytoplasm contains the _____ in which organelles are suspended.

mitochondria

Multiple copies of _____ are located within the cytoplasm.

phospholipid membranes

Mitochondria are surrounded by ______ that separate them from the cytosol.

adenosine triphosphate (ATP)

The mitochondria are responsible for energy production through aerobic metabolism by producing molecules containing high-energy bonds, such as _______.

Smooth ER

It is involved in lipid synthesis.

Rough ER

It contains ribosomes on its outer surface and forms transport vesicles.

Golgi apparatus

It is responsible for the production of secretory vesicles and new membrane components, and also for the packaging of lysosomes.

Lysosomes

Vesicles containing digestive enzymes for the degradation of injured cells).

Peroxisomes

Carry enzymes that neutralize potentially harmful free radicals.

triplet codes

The genetic code is read as an array of ______, a sequence of three bases that specifies the identity of a single amino acid.

Tissue-specific mRNA

_______ can be potentially used for the identification of biological evidence.

translation

The proteins are synthesized in a process known as _____, in which amino acids are assembled based on the codons derived from the triplet code of the DNA contained in the sequence of the mRNA strand.

MicroRNAs (miRNAs)

_______ are short RNA molecules that are 21–23 nucleotides in length.

eukaryotic organisms

In _______, miRNAs function as *negative regulators* of gene expression.

Intergenic miRNA genes

____ are distinct transcriptional units that are found in genomic regions.

Intronic miRNAs

_____ reside within the introns of protein-coding and noncoding genes.

Exonic miRNAs

______ are rare in eukaryotic genomes and reside in genomic regions that overlap with an exon and an intron of a pseudogene, which is a noncoding gene or is no longer transcribed.

monocistronic miRNA

A _______ has a single transcriptional unit with its own promoter.

polycistronic miRNAs

In ______, several miRNAs reside as a cluster of transcriptional units with a shared promoter.

RNA polymerase II

miRNAs are transcribed by _______.

Nascent transcripts

______, referred to as primary transcripts (pri-miRNAs), can be several hundred to thousands of nucleotides in length.

Fingerprints

_____ are ridge skin impressions that are usually collected at crime scenes, and shed skin tissue is a source of DNA for human identification.

dorsal area

The skin of the _______ of the body is usually thicker than that of the ventral area of the body.

Epidermis

The outer layer of the skin. It also contains melanocytes that produce the skin pigment melanin.

Basal Layer

Contains newly formed keratinocytes that are proliferative.

cornified layer

As the cells reach the ______, these cells are filled with keratin filaments and are differentiated into corneocytes, which are dead, and terminally differentiated keratinocytes.

spinous and granular layers

Once the migrating keratinocytes reach the ______, the keratinocytes become nonproliferating and partially differentiated.

Dermis

The middle layer of the skin.

Dermis

It is filled with fibrous collagen proteins secreted by fibroblasts and contains hair follicles and sweat glands.

Dermis

It contains blood, lymph vessels, and nerves.

Subcutaneous layer

The deepest layer of the skin.

Subcutaneous layer

It consists of collagen networks and adipose tissue to prevent loss of heat.

Touched Evidence

Evidence from skin contact; which can be collected and used for forensic DNA analysis.

Transfer DNA

The DNA recovered from touched evidence.

polymerase chain reaction amplification technique

The development of the ________ made it possible to analyze very small quantities of DNA in hair, and the use of hair as evidence of identification has become more significant.

hair shaft

The human ______ is a keratinized cylindrical structure.

Medulla

The center or core of the hair.

Cortex

It surrounds the medulla; which is the outer layer of the hair shaft.

Cuticle

Consists of overlapping layers of flattened keratinized cells that protect the hair.

hair follicles

Hairs are produced in ___.

Bulge

Exports the stem cells that migrate down and give rise to bulb cells.

Matrix Cells

These generate the hair shaft cells, which are located at the lower portion of the bulb.

Dermal Papilla

It is situated at the base of the bulb and contains cells that regulate hair growth, which is nourished by blood vessels and nerves.

Anagen Phase

The growing phase of hair.

Catagen Phase

Occurs at the end of the anagen phase, where the matrix cells enter and undergo cell death.

Telogen Phase

Resting stage of the hair.

Nuclear DNA analysis

_____ is usually accomplished by using freshly plucked hair roots because cells at the root region may contain nuclear DNA.

telogen hairs

Multiple _____ with roots are necessary to isolate enough nuclear DNA.

sequence polymorphism

A ______ analysis of mtDNA from hair can be carried out. mtDNA is maternally inherited, which is useful to identify maternal relatives but cannot be used to perform paternity testing.

Heteroplasmy

The heterogeneous pool of mtDNA molecules.

melanocytes

Hair follicle _______ are formed at the beginning of each hair cycle and die at the end of the cycle. They’re are located in the bulb hair follicle.

Melanosome

an organelle of melanin.

dendritic processes

The melanosomes are transferred to neighboring keratinocytes though _______.

206 bones

An adult human skeleton consists of_____.

cortical bone

The shaft of a long bone, such as an arm or a leg bone, consists largely of an outer layer of _____, which is strong and solid.

marrow cavity

The shaft of a long bone forms a ______, which is filled with a specialized type of connective tissue called bone marrow.

bone marrow

The shaft of a long bone forms a marrow cavity, which is filled with a specialized type of connective tissue called _______.

Epiphysis

The portion at each end of a long bone, which is composed largely of cancellous bone and can bear the force of compression.

flat bone

A ______ can have primarily either cortical or cancellous bone.

skull bone

A ______ usually consists of largely cortical bone.

bone matrix

The ______ consists of an inorganic and an organic matrix.

inorganic bone matrix

*Calcium* and *phosphorus* are the major components of the _______, which consists mainly of hydroxyapatite crystals.

organic bone matrix

The _______ consists of collagens, primarily type I collagen, which are insoluble fibrous proteins.

osteoprogenitor cells

Developing bones contain small numbers of ________.