Biology Review Notes: Respiratory, Circulatory, and Genetics (Non-Mendelian Inheritance, ABO, and Sex-Linked Traits)

RESPIRATORY SYSTEM

  • Definition: Respiration – the exchange of gases in the body.
  • Major parts (in order):
    • Nose: entrance of oxygen into the body.
    • Nasal Cavity: lined with mucus membrane and cilia (tiny hairs) to filter particles.
    • Pharynx (throat): contains the epiglottis which closes off the opening of the trachea when you swallow.
    • Larynx (voice box): involved in sound production.
    • Trachea (windpipe): filters the air we inhale and directs it to the tracheal branches into the bronchi.
    • Lungs: main organs of the respiratory system.
    • Bronchi (singular: bronchus): extension of the trachea that divides the left and right lungs.
    • Bronchioles: hair-like tubes that connect to the alveoli.
    • Alveoli: site of gas exchange; surrounded by blood vessels.
  • Mnemonic to remember order: “No Naughty People Like To Laugh Before Being Angry”
    • No -> Nose
    • Naughty -> Nasal Cavity
    • People -> Pharynx
    • Like -> Larynx
    • To -> Trachea
    • Laugh -> Bronchi
    • Before -> Bronchioles
    • Being -> Alveoli
    • Angry -> Alveoli
    • Note: During gas exchange, capillaries exchange oxygen and carbon dioxide between blood and tissues.
  • Gas exchange (quick summary): Oxygen diffuses from alveoli into blood; carbon dioxide diffuses from blood into alveoli to be exhaled.

CIRCULATORY SYSTEM

  • Veins vs Arteries:
    • Veins – carry blood TO the heart.
    • Arteries – carry blood AWAY from the heart.
  • Four chambers of the heart:
    1. Right Atrium – receives deoxygenated blood from the body through large veins (vena cava).
    2. Right Ventricle – receives deoxygenated blood from the right atrium and pumps blood to the pulmonary arteries.
    3. Left Atrium – receives oxygenated blood from the lungs and passes it to the left ventricle.
    4. Left Ventricle – pumps oxygenated blood into the aorta.
  • Memory aid: Atrium (right/left) – receives blood that comes into the heart; Ventricles (right/left) – pumping chambers.
  • Flow diagram (simplified sample flow of blood):
    • Vena cava → Right Atrium → Right Ventricle → Pulmonary Artery → Lungs → Pulmonary Vein → Left Atrium → Left Ventricle → Aorta
  • Trivia: The increase in breathing rate and heart rate during running is because the respiratory and circulatory systems work together to supply oxygen and nutrients needed for muscle activity.

COMMON DISEASES OF RESPIRATORY AND CIRCULATORY SYSTEM

  1. Lung Cancer – main cause: smoking and exposure to cigarettes.
  2. Asthma – main causes: pollution, smoking.
  3. Pneumonia – main causes: bacteria, viruses, and fungi.

GENETICS

  • Genes: The basic unit of heredity. Segments of DNA that carry hereditary information.
  • Location: Can be found in chromosomes, nucleus, and DNA.
  • Chromosome: A structure that organizes and keeps genes in place; its shape does not affect gene use.
  • DNA (Deoxyribonucleic Acid):
    • Found in plant and animal cells.
    • A nucleic acid that carries information necessary for inheritance.
    • Composed of nucleotides: extA,extT,extC,extGext{A}, ext{T}, ext{C}, ext{G}
    • Base pairing: A↔T, extandC↔G.A \leftrightarrow T,\ ext{ and } C \leftrightarrow G.
  • Relationship between DNA, genes, and chromosomes:
    • Chromosomes contain genes, which are made of DNA.
    • DNA makes up chromosomes, and genes are specific DNA segments.
  • Very brief view of the chromosome model used to locate genes: mark genes at fixed points along a chromosome diagram.
  • Note: DNA exists in both plant and animal cells; it carries information necessary for inheritance.

NON-MENDELIAN INHERITANCE

  • Genotype – a unique sequence of DNA; represented by letters (e.g., BB, Bb, bb).
  • Phenotype – an observable trait (e.g., brown hair, roan cow, Type A blood).
  • Types (as listed in the notes):
  1. Codominance
    • Definition: Both parental traits display simultaneously and equally in offspring.
    • Example: Roan coat color in cattle (RW) x white (WW): Offspring genotypes → 50% RW, 50% WW; phenotypes → 50% Roan, 50% White.
    • Genotype ratio: 1:1 (RW:WW); Phenotype ratio: 1:1 (Roan:White).
  2. Incomplete Dominance
    • Definition: Blending of alleles in the genotype or blending of parental traits to form a new phenotype.
    • Example: Red (RR) x White (rr) yields Pink (Rr).
    • Punnett square note: If red flowers (RR) are crossed with white flowers (rr), all offspring are heterozygous (Rr) and pink in phenotype.
    • Genotype: 100% Rr; Phenotype: 100% Pink.
    • Genotype ratio: 1; Phenotype ratio: 1.
  3. Multiple Alleles
    • Definition: More than two phenotypes are expressed in offspring.
    • Classic example: ABO blood types – Type A, Type B, Type AB, Type O.
    • Genotypes for ABO system (illustrative): IAIA (Type A, Homozygous Dominant), IAi (Type A, Heterozygous), IBIB (Type B, Homozygous Dominant), IBi (Type B, Heterozygous), IAIB (Type AB), ii (Type O).
    • Punnett square example (cross): A person with blood type A (IAi) and a person with blood type B (IBi) mate.
    • Possible offspring genotypes: IAIA, IAi, IAIB, IBi, ii, etc. (in standard practice, the expected distribution is 25% IAIA, 25% IAi, 25% IBi, 25% ii; phenotypes: Type A (IAIA or IAi) 50%, Type B (IBi) 25%, Type O (ii) 25%, Type AB (IAIB) 25%). Note: The notes show IAIA, IAi, IBi, ii as the genotypes and Type A, Type B, Type AB, Type O as the phenotypes with equal 25% distribution in that particular schematic—conceptually this demonstrates multiple alleles and codominance considerations.
  4. Sex-linked traits
    • Involves genes on sex chromosomes (XX for female, XY for male).
    • Common examples: Colorblindness and hemophilia.
    • Example table (colorblindness):
    • GENOTYPE: XBXB → Unaffected daughter
    • XBXb → Carrier daughter
    • XBY → Unaffected son
    • XbY → Affected son
  • Note: Explanations indicate a standard approach to sex-linked traits using Punnett squares with the X chromosome for the gene in question. (Tables are noted as acceptable for index-card style study aids.)

PUNNETT SQUARES AND EXAMPLES (REVIEW)

  • Important general note: In many exercises, exponents on the X chromosome in Punnett squares are used to mark sex-linked inheritance patterns.
PUNNETT SQUARE EXAMPLE: Colorblindness (X-linked) – Normal female (XBXB) x Colorblind man (XbY)
  • Gametes from normal female: XB and XB
  • Gametes from colorblind man: Xb and Y
  • Punnett results:
    • XB Xb → XBXb (carrier daughter)
    • XB Y → XBY (unaffected son)
    • XB Xb → XBXb (carrier daughter)
    • XB Y → XBY (unaffected son)
  • Genotype distribution: 50% XBXb (carrier daughters), 50% XBY (unaffected sons)
  • Phenotype distribution: 50% carrier daughters, 50% unaffected sons
  • Genotypic ratio: 2:2 or 1:1; Phenotypic ratio: 2:2 or 1:1
HEMOPHILIA PATTERN (X-linked recessive) – Genotype vs Phenotype
  • Common genotype-phenotype map:
    • XX → Normal Female
    • XY → Normal Male
    • XhX → Female, Carrier
    • XhXh → Hemophiliac Female
    • XhY → Hemophiliac Male
  • Note: This table is commonly used on index cards for quick reference.
PUNNETT SQUARE EXAMPLE: Hemophilia cross – Carrier female XhX with affected male XhY
  • Gametes from carrier female: Xh and X
  • Gametes from affected male: Xh and Y
  • Punnett results:
    • Xh Xh → XhXh (Hemophiliac Female)
    • Xh Y → XhY (Hemophiliac Male)
    • X Xh → XhX (Carrier Female)
    • X Y → XY (Normal Male)
  • Genotype distribution: 25% XhXh, 25% XhY, 25% XhX, 25% XY
  • Phenotype distribution: 25% Hemophiliac Female, 25% Hemophiliac Male, 25% Carrier Female, 25% Normal Male
  • Genotypic ratio: 1:1:1:1; Phenotypic ratio: 1:1:1:1