Human Biology: Genetics, Tissues, Blood, and the Cardiovascular System

Comprehensive practice flashcards covering human chromosome inheritance, Mendelian and non-Mendelian genetics, tissue classification, blood physiology, and cardiovascular function.

Chromosomes

Structures composed of DNA and organizational proteins located in the nucleus that carry genetic instructions within genes; humans have 46 in 23 pairs.

Chromatin

The collective network of DNA and structural proteins that appears as a tangled mass of thin threads when a cell is not dividing.

Autosomes

The 22 pairs of chromosomes in human cells that are found in both males and females and do not determine gender.

Sex Chromosomes

The single pair of chromosomes that determine biological gender, consisting of $X$ and $Y$ in males and two $X$ chromosomes in females.

SRY Gene

The sex-determining region $Y$ gene located on the short arm of the $Y$ chromosome that triggers the development of male testes.

Karyotype

A visual display of the chromosomes present in a cell, arranged into paired homologues according to size, shape, and banding pattern.

Sister Chromatids

Two identical parts of a duplicated chromosome containing the same genes, joined together at the centromere prior to nuclear division.

Centromere

The constricted region of a chromosome that holds sister chromatids together and attaches to spindle fibers until dividing during mitosis or meiosis II.

Cell Cycle

The orderly sequence of stages in a cell comprising interphase ($G_1$, $S$, and $G_2$) and cell division (mitosis and cytokinesis).

$G_1$ Stage

The phase of interphase during which the cell performs normal functions, doubles its organelles, and gathers materials needed for DNA synthesis.

S Stage

The synthesis stage of interphase where DNA replication occurs, resulting in each chromosome consisting of two identical sister chromatids.

$G_2$ Stage

The phase of interphase following DNA replication during which the cell synthesizes the proteins necessary for cell division.

$G_0$ Stage

A permanently or temporarily arrested non-dividing state in which cells perform their normal biological functions without replicating DNA.

Apoptosis

Programmed cell death that eliminates cells that are damaged beyond repair or no longer needed by the body.

Cell Cycle Checkpoints

Regulatory stopping points ($G_1$, $G_2$, and mitotic checkpoints) that delay cell cycle progression until critical molecular conditions are met.

$G_1$ Checkpoint

The primary checkpoint of the cell cycle where available nutrients, growth signals, and DNA integrity are evaluated before the cell commits to division.

p53 Protein

A regulatory protein that checks DNA integrity and can halt the cell cycle at the $G_1$ checkpoint to initiate repair or trigger apoptosis.

Mitotic Spindle

A microtubule assembly originating from duplicated centrosomes that separates sister chromatids during mitosis.

Centrosome

The primary microtubule-organizing center of the cell containing a pair of centrioles, which duplicates and forms the spindle poles during division.

Cleavage Furrow

An indentation around the cell circumference formed by an actin contractile ring that pinches the cytoplasm into two daughter cells during cytokinesis.

Meiosis

A reduction division process consisting of two consecutive cell divisions without an intervening interphase, yielding four genetically distinct haploid ($n$) cells.

Homologous Chromosomes

Pairs of matching chromosomes that possess the same size, shape, and gene loci for particular traits, with one inherited from each parent.

Synapsis

The pairing of homologous chromosomes side by side along their lengths during prophase I of meiosis, allowing crossing-over to take place.

Crossing-Over

The reciprocal exchange of genetic material between non-sister chromatids of a homologous pair during prophase I of meiosis, producing non-identical chromatids.

Spermatogenesis

The continuous production of sperm in the testes starting at puberty, producing approximately $300{,}000$ sperm per minute and over $400\text{ million}$ per day.

Oogenesis

The formation of female egg cells in the ovaries that begins during embryonic development and yields one functional haploid egg and polar bodies.

Williams Syndrome

A genetic deletion syndrome caused by the loss of an end piece of chromosome 7, characterized by a missing elastin gene, premature skin aging, turned-up nose, and strong verbal and musical skills.

Cri du Chat Syndrome

A chromosomal deletion disorder where chromosome 5 is missing an end piece, causing facial abnormalities, intellectual disabilities, and an abnormal larynx that results in a cat-like cry.

Gene

A specific nucleotide sequence of DNA located on a chromosome that codes for a functional protein product.

Allele

An alternate form of a particular gene having a distinct nucleotide sequence that codes for a specific variation of a protein.

Phenotype

The physical and outward appearance or observable biochemical characteristic of an individual organism.

Genotype

The specific genetic composition or combination of inherited alleles present in an individual or zygote.

Dominant Allele

An allele that masks the expression of an alternate recessive allele, requiring only one copy to produce its characteristic phenotype.

Recessive Allele

An allele whose phenotypic expression is masked by a dominant allele and can only be observed when two copies are present in a homozygous state.

Homozygous

A genotypic state in which an organism possesses two identical alleles at a specific gene locus (e.g., $FF$ or $ff$).

Heterozygous

A genotypic condition in which an organism carries two different alleles for a specific gene locus (e.g., $Ff$).

Monohybrid Cross

A genetic cross designed to examine the inheritance and phenotypic outcome of a single trait.

Punnett Square

A grid diagram used by geneticists to calculate and predict all possible allele combinations and probabilities resulting from a genetic cross.

Testcross

A cross between an organism showing a dominant phenotype and an organism with a homozygous recessive phenotype to determine whether the dominant parent is homozygous or heterozygous.

Dihybrid Cross

A mating between individuals that differ in two distinct inherited traits governed by separate gene loci.

9:3:3:1 Phenotypic Ratio

The classic phenotypic distribution expected among offspring of a dihybrid cross involving two heterozygous individuals ($FfSs \times FfSs$) exhibiting simple dominance.

Autosomal Dominant Disorder

A hereditary condition where individuals carrying either one or two copies of the mutant allele ($Aa$ or $AA$) manifest the disease phenotype.

Autosomal Recessive Disorder

A genetic disease that manifests only in individuals who inherit two copies of the mutated recessive allele ($aa$).

Carrier

A clinically unaffected heterozygous individual ($Aa$) who carries a recessive disease allele capable of being transmitted to offspring.

Pedigree

A charted representation of family lineages utilizing standardized symbols (squares for males, circles for females) to analyze patterns of inheritance across generations.

Sickle Cell Disease

A genetic hemolytic anemia caused by two copies of the abnormal hemoglobin gene ($\text{HbS}\text{HbS}$), resulting in rigid, crescent-shaped erythrocytes that block small blood vessels.

Sickle Cell Trait

The heterozygous state ($\text{HbS}\text{HbA}$) wherein individuals have one normal and one mutated hemoglobin allele, typically remaining symptom-free under standard conditions.

Malaria Protection Advantage

An evolutionary survival advantage in which sickle cell carriers ($\text{HbS}\text{HbA}$) resist severe malaria because macrophages rapidly destroy parasite-infected red blood cells.

Polygenic Inheritance

A mode of inheritance wherein a single phenotypic trait (such as height or skin color) is governed by the additive effects of two or more independent pairs of alleles.

Multifactorial Traits

Characteristics governed by multiple genes (polygenes) that are also subject to substantial modification by environmental influences.

Pleiotropy

A genetic phenomenon where a single mutated gene produces multiple distinct, seemingly unrelated physical effects throughout the body.

Marfan Syndrome

An autosomal condition caused by a defective fibrillin gene resulting in extensive connective tissue abnormalities affecting the skeleton, eyes, heart, lungs, and skin.

Incomplete Dominance

A pattern of inheritance in which the heterozygous phenotype is an intermediate blend between the two homozygous phenotypes (e.g., wavy hair from curly and straight hair alleles).

Codominance

An inheritance pattern where both alleles are equally and simultaneously expressed in a heterozygote, such as in blood type $AB$.

Sex-Linked Trait

An inherited characteristic controlled by genes situated on a sex chromosome, most commonly found on the $X$ chromosome.

Color Blindness

An $X$-linked recessive condition that occurs more frequently in males because they require only one inherited mutant allele on their single $X$ chromosome.

Tissue

A collection of specialized cells of similar structure that cooperate to perform a common physiological function within an organism.

Connective Tissue

One of the four primary tissue types that binds, supports, and protects body structures; it consists of specialized cells, ground substance, and protein fibers.

Ground Substance

The noncellular, hydrated material filling the space between cells and fibers within connective tissue matrices.

Collagen Fibers

Flexible and strong protein fibers found within connective tissue that provide tensile strength and structural support.

Elastic Fibers

Connective tissue fibers composed of the protein elastin that possess the ability to stretch and recoil.

Loose Connective Tissue

A fibrous connective tissue category with an open framework of fibers found beneath epithelial tissues, around blood vessels, and surrounding organs.

Dense Fibrous Connective Tissue

Connective tissue packed with parallel collagen fibers that provides strong attachments in structures such as tendons and ligaments.

Adipose Tissue

A specialized loose connective tissue containing adipocytes that stores lipids for energy, insulates against heat loss, and cushions organs.

Supportive Connective Tissue

A functional class of rigid or semi-rigid connective tissues consisting of cartilage and bone that provides posture, leverage, and physical protection.

Cartilage

A solid, flexible, avascular supportive connective tissue consisting of chondrocytes embedded within small spaces called lacunae.

Lacunae

Tiny chambers or cavities within the extracellular matrix of cartilage and bone that enclose chondrocytes or osteocytes.

Hyaline Cartilage

The most common and flexible variety of cartilage containing fine collagen fibers, found at the ends of long bones, the nose tip, and the fetal skeleton.

Fibrocartilage

The toughest and least flexible cartilage form, reinforced with thick collagen fibers to withstand pressure in intervertebral disks and knee joints.

Elastic Cartilage

The most flexible type of cartilage, rich in elastic fibers, which maintains the structural shape of external ears.

Compact Bone

Dense osseous tissue forming the shafts of long bones, organized into repeating cylindrical structural subunits termed osteons.

Osteon

The basic cylindrical structural unit of compact bone consisting of concentric matrix lamellae surrounding a neurovascular central canal.

Spongy Bone

Lighter, porous osseous tissue with thin, interlacing trabeculae situated within the ends of long bones.

Muscular Tissue

Tissue specialized for contraction and body movement composed of elongated muscle fibers utilizing actin and myosin filaments.

Skeletal Muscle

Voluntary, striated muscle containing multinucleated cylindrical fibers attached to bones for bodily locomotion.

Smooth Muscle

Involuntary, non-striated muscle containing spindle-shaped cells with single central nuclei, located in the walls of internal organs and blood vessels.

Cardiac Muscle

Involuntary, striated muscle located exclusively in heart walls, composed of branching uninucleated cells united by intercalated disks.

Nervous Tissue

Tissue located in the brain, spinal cord, and nerves responsible for sensory reception, impulse conduction, and data processing.

Neurons

Electrically excitable cells of nervous tissue that generate, conduct, and transmit nerve impulses and neurotransmitters.

Neuroglia

Non-conducting supportive cells of the nervous system that physically protect, insulate, and nourish neighboring neurons.

Epidermis

The thin, stratified squamous epithelial surface layer of skin that is dead, keratinized, and waterproof.

Dermis

The thick inner layer of skin beneath the epidermis composed of dense connective tissue containing glands, hair follicles, nerves, and blood vessels.

Hypodermis

The subcutaneous layer situated directly beneath the dermis, primarily composed of adipose tissue that provides cushioning and thermal insulation.

Body Cavities

Internal spaces in the body that house and protect organs; divided into a posterior dorsal cavity and an anterior ventral cavity separated by the diaphragm.

Homeostasis

The physiological capacity of the body to maintain a dynamic, relatively constant internal environment despite fluctuating external conditions.

Negative Feedback

The primary homeostatic control mechanism wherein a sensor detects a stimulus and a control center activates an effector to reverse the deviation back to normal.

Blood

A fluid connective tissue consisting of formed elements suspended in liquid plasma, comprising about $8\%$ of total body weight ($4\text{ to }6\,\text{L}$ in adults).

Plasma

The liquid, noncellular extracellular matrix of blood, accounting for approximately $55\%$ of whole blood volume and composed of $90\%$ water, salts, and proteins.

Formed Elements

The cellular fractions of blood, comprising red blood cells, white blood cells, and platelets, that together constitute $45\%$ of whole blood volume.

Buffy Coat

The thin, white intermediate layer visible after centrifuging whole blood that contains leukocytes and platelets, representing less than $1\%$ of blood volume.

Hematocrit

The volume percentage of whole blood that consists of erythrocytes after centrifugation, typically measuring about $45\%$.

Albumin

The most abundant plasma protein synthesized by the liver, functioning chiefly to maintain osmotic pressure and regulate blood volume.

Acidosis

A pathological state in which arterial blood $\text{pH}$ drops below the normal range ($<7.35$), triggering an increased respiration rate to expel carbon dioxide.

Alkalosis

A physiological condition characterized by blood $\text{pH}$ rising above the normal limit of $7.45$, prompting a compensatory reduction in breathing rate.

Erythrocytes

Salmon-colored, anucleate, biconcave disks filled with hemoglobin that transport oxygen; numbering $4\text{ to }6\text{ million per mm}^3$ with a lifespan of $100\text{ to }120\,\text{days}$.

Hemoglobin

An iron-containing respiratory pigment protein packaged in red blood cells that reversibly binds and transports oxygen molecules.

Leukocytes

Nucleated white blood cells functioning in immune defense against disease, normally numbering $4{,}800\text{ to }10{,}800\text{ per mm}^3$ of blood.

Diapedesis

The process by which white blood cells actively slip through intact capillary walls to enter surrounding inflamed tissues.

Positive Chemotaxis

The directional migration of white blood cells toward high concentrations of chemical signaling molecules released by damaged cells or pathogens.

Granulocytes

A subgroup of white blood cells possessing prominent stained cytoplasmic granules and lobed nuclei, including neutrophils, eosinophils, and basophils.