CBSE 2026-27 Class 12 Biology Chapter 4 Principles of Inheritance Variation syllabus topics

https://cdnbbsr.s3waas.gov.in/s3kv03b7b00c918a9674f4256026aa…

ls -la /home/daytona/workspace/ 2>/dev/null || echo "workspace not found"

mkdir -p /home/daytona/workspace/bio-ch4-notes

~/bio-ch4-notes/generate_pdf.py

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import cm, mm
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, PageBreak, KeepTogether
)
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.platypus import BaseDocTemplate, PageTemplate, Frame

OUTPUT = "/home/daytona/workspace/bio-ch4-notes/Ch4_Inheritance_Variation_Notes.pdf"

# ── Colours ──────────────────────────────────────────────────────────────────
DARK_BLUE   = colors.HexColor("#1a237e")
MID_BLUE    = colors.HexColor("#1565c0")
LIGHT_BLUE  = colors.HexColor("#e3f2fd")
GREEN       = colors.HexColor("#1b5e20")
LIGHT_GREEN = colors.HexColor("#e8f5e9")
ORANGE      = colors.HexColor("#e65100")
YELLOW_BG   = colors.HexColor("#fffde7")
GREY_BG     = colors.HexColor("#f5f5f5")
RED         = colors.HexColor("#b71c1c")
TEAL        = colors.HexColor("#006064")
PURPLE      = colors.HexColor("#4a148c")

# ── Styles ────────────────────────────────────────────────────────────────────
ss = getSampleStyleSheet()

def make_style(name, parent="Normal", **kwargs):
    return ParagraphStyle(name, parent=ss[parent], **kwargs)

title_style = make_style("MyTitle", parent="Title",
    fontSize=22, textColor=DARK_BLUE, spaceAfter=4,
    fontName="Helvetica-Bold", alignment=TA_CENTER)

subtitle_style = make_style("MySubtitle",
    fontSize=11, textColor=MID_BLUE, spaceAfter=2,
    fontName="Helvetica", alignment=TA_CENTER)

chapter_style = make_style("ChapterH",
    fontSize=15, textColor=colors.white, spaceAfter=6, spaceBefore=14,
    fontName="Helvetica-Bold", backColor=DARK_BLUE,
    borderPad=6, leading=20)

topic_style = make_style("TopicH",
    fontSize=12, textColor=colors.white, spaceAfter=4, spaceBefore=10,
    fontName="Helvetica-Bold", backColor=MID_BLUE,
    borderPad=5, leading=17)

sub_style = make_style("SubH",
    fontSize=11, textColor=DARK_BLUE, spaceAfter=3, spaceBefore=6,
    fontName="Helvetica-Bold")

body_style = make_style("MyBody",
    fontSize=9.5, leading=14, spaceAfter=3,
    fontName="Helvetica")

bullet_style = make_style("MyBullet",
    fontSize=9.5, leading=13, spaceAfter=2,
    leftIndent=14, firstLineIndent=0,
    fontName="Helvetica")

mnemonic_style = make_style("Mnemonic",
    fontSize=9.5, leading=13, spaceAfter=4,
    fontName="Helvetica-BoldOblique", textColor=PURPLE,
    backColor=YELLOW_BG, borderPad=6, leftIndent=8, rightIndent=8)

note_style = make_style("Note",
    fontSize=9, leading=13, spaceAfter=4,
    fontName="Helvetica-Oblique", textColor=TEAL,
    backColor=LIGHT_GREEN, borderPad=5, leftIndent=8, rightIndent=8)

mcq_q_style = make_style("McqQ",
    fontSize=10, leading=14, spaceAfter=3, spaceBefore=6,
    fontName="Helvetica-Bold", textColor=DARK_BLUE)

mcq_opt_style = make_style("McqOpt",
    fontSize=9.5, leading=13, spaceAfter=1, leftIndent=16,
    fontName="Helvetica")

answer_style = make_style("Ans",
    fontSize=9.5, leading=13, spaceAfter=2,
    fontName="Helvetica", textColor=GREEN)

# ── Helper builders ───────────────────────────────────────────────────────────
def h_chapter(text):
    return [Paragraph(text, chapter_style), Spacer(1, 2)]

def h_topic(text):
    return [Spacer(1, 4), Paragraph(text, topic_style), Spacer(1, 3)]

def h_sub(text):
    return [Paragraph(text, sub_style)]

def body(text):
    return Paragraph(text, body_style)

def bullet(text):
    return Paragraph(f"•  {text}", bullet_style)

def mnemonic(text):
    return Paragraph(f"<b>Mnemonic:</b> {text}", mnemonic_style)

def note(text):
    return Paragraph(f"<b>Note:</b> {text}", note_style)

def spacer(h=4):
    return Spacer(1, h)

def hr():
    return HRFlowable(width="100%", thickness=0.5, color=colors.lightgrey, spaceAfter=4, spaceBefore=4)

def make_table(data, col_widths=None, header_bg=DARK_BLUE, header_fg=colors.white,
               alt_bg=LIGHT_BLUE, row_bg=colors.white, font_size=8.5):
    style = TableStyle([
        ("BACKGROUND",   (0,0), (-1,0),  header_bg),
        ("TEXTCOLOR",    (0,0), (-1,0),  header_fg),
        ("FONTNAME",     (0,0), (-1,0),  "Helvetica-Bold"),
        ("FONTSIZE",     (0,0), (-1,-1), font_size),
        ("ALIGN",        (0,0), (-1,-1), "LEFT"),
        ("VALIGN",       (0,0), (-1,-1), "MIDDLE"),
        ("ROWBACKGROUNDS",(0,1),(-1,-1), [row_bg, alt_bg]),
        ("GRID",         (0,0), (-1,-1), 0.4, colors.HexColor("#b0bec5")),
        ("LEFTPADDING",  (0,0), (-1,-1), 6),
        ("RIGHTPADDING", (0,0), (-1,-1), 6),
        ("TOPPADDING",   (0,0), (-1,-1), 4),
        ("BOTTOMPADDING",(0,0), (-1,-1), 4),
    ])
    t = Table(data, colWidths=col_widths, repeatRows=1)
    t.setStyle(style)
    return t

def punnett_table(col_headers, row_headers, cells, title="Punnett Square"):
    data = [[""] + col_headers]
    for rh, row in zip(row_headers, cells):
        data.append([rh] + row)
    style = TableStyle([
        ("BACKGROUND",   (0,0), (-1,0),  MID_BLUE),
        ("BACKGROUND",   (0,0), (0,-1),  MID_BLUE),
        ("TEXTCOLOR",    (0,0), (-1,0),  colors.white),
        ("TEXTCOLOR",    (0,0), (0,-1),  colors.white),
        ("FONTNAME",     (0,0), (-1,-1), "Helvetica-Bold"),
        ("FONTSIZE",     (0,0), (-1,-1), 9),
        ("ALIGN",        (0,0), (-1,-1), "CENTER"),
        ("VALIGN",       (0,0), (-1,-1), "MIDDLE"),
        ("GRID",         (0,0), (-1,-1), 0.8, DARK_BLUE),
        ("LEFTPADDING",  (0,0), (-1,-1), 10),
        ("RIGHTPADDING", (0,0), (-1,-1), 10),
        ("TOPPADDING",   (0,0), (-1,-1), 7),
        ("BOTTOMPADDING",(0,0), (-1,-1), 7),
        ("ROWBACKGROUNDS",(1,1),(-1,-1), [LIGHT_BLUE, LIGHT_GREEN]),
    ])
    t = Table(data)
    t.setStyle(style)
    return t

# ── Build story ────────────────────────────────────────────────────────────────
story = []

# Cover block
story += [
    spacer(30),
    Paragraph("Class 12 Biology", subtitle_style),
    Paragraph("Chapter 4", subtitle_style),
    Paragraph("Principles of Inheritance", title_style),
    Paragraph("and Variation", title_style),
    spacer(4),
    Paragraph("Complete NCERT Notes | CBSE 2026-27 Board Level", subtitle_style),
    spacer(6),
    HRFlowable(width="60%", thickness=2, color=MID_BLUE, spaceAfter=6),
    Paragraph("Covers: Mendel's Laws | Deviations | Sex Determination | Linkage |<br/>Mutation | Pedigree | Genetic Disorders | MCQs", subtitle_style),
    spacer(30),
    PageBreak(),
]

# ═══════════════════════════════════════════════════════════════════
# SECTION: KEY TERMS
# ═══════════════════════════════════════════════════════════════════
story += h_chapter("KEY TERMS")

terms_data = [
    ["Term", "Definition"],
    ["Genetics", "Study of inheritance and variation"],
    ["Heredity", "Transmission of characters from parents to offspring"],
    ["Variation", "Differences between parents and offspring"],
    ["Gene", "A unit of inheritance (discrete factor)"],
    ["Allele", "Alternative forms of a gene (e.g. T and t)"],
    ["Homozygous", "Both alleles are same (TT or tt) - true breeding"],
    ["Heterozygous", "Alleles are different (Tt)"],
    ["Phenotype", "Observable character (e.g. Tall)"],
    ["Genotype", "Genetic makeup (e.g. Tt)"],
    ["Dominant", "Allele that expresses in heterozygous condition"],
    ["Recessive", "Allele that is masked in heterozygous condition"],
]
story.append(make_table(terms_data, col_widths=[4*cm, 13*cm]))
story.append(spacer(6))
story.append(mnemonic('"Gene Hunters Have Absolutely Perfect Genuine Dedication" -> G-ene, H-eredity, H-omozygous, A-llele, P-henotype, G-enotype, D-ominant'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 1: MENDEL
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 1: Mendel and His Experiments")

story += h_sub("Why Mendel Succeeded")
for t in [
    "Chose <b>pea plant (Pisum sativum)</b> - short life cycle, easy to grow, large offspring",
    "Studied <b>7 pairs of contrasting characters</b> one at a time",
    "Used <b>statistics and mathematics</b> - a new approach in biology",
    "Maintained <b>large sample sizes</b> to reduce error",
]:
    story.append(bullet(t))

story.append(spacer(6))
story += h_sub("Mendel's 7 Characters in Pea Plant")

chars_data = [
    ["Character", "Dominant Trait", "Recessive Trait"],
    ["Stem height", "Tall (T)", "Dwarf (t)"],
    ["Seed shape", "Round (R)", "Wrinkled (r)"],
    ["Seed colour", "Yellow (Y)", "Green (y)"],
    ["Pod shape", "Inflated (I)", "Constricted (i)"],
    ["Pod colour", "Green (G)", "Yellow (g)"],
    ["Flower position", "Axial (A)", "Terminal (a)"],
    ["Flower colour", "Violet (V)", "White (v)"],
]
story.append(make_table(chars_data, col_widths=[5*cm, 6*cm, 6*cm]))
story.append(spacer(4))
story.append(mnemonic('"The Silly Yellow Pigs Go Around Villages" -> T-all, S-hape(seed), Y-ellow, P-od(shape), G-reen(pod), A-xial, V-iolet'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 2: MENDEL'S LAWS
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 2: Mendel's Laws of Inheritance")

story += h_sub("Law 1 - Law of Dominance")
for t in [
    "Characters are controlled by <b>discrete units called factors (genes)</b>",
    "Factors occur <b>in pairs</b>",
    "In a heterozygous pair, one factor <b>dominates</b> the other",
    "Dominant allele expresses itself; recessive stays hidden",
]:
    story.append(bullet(t))

story.append(spacer(6))
story += h_sub("Law 2 - Law of Segregation")
story.append(body('<i>"During gamete formation, the two alleles of a character pair in parents segregate so that a gamete receives only ONE of the two alleles."</i>'))
story.append(spacer(4))
story += h_sub("Monohybrid Cross: TT x tt")

mono_table = punnett_table(
    col_headers=["T", "t"],
    row_headers=["T", "t"],
    cells=[["TT (Tall)", "Tt (Tall)"],
           ["Tt (Tall)", "tt (Dwarf)"]],
)
story.append(mono_table)
story.append(spacer(4))

ratios_mono = [
    ["Ratio Type", "F1", "F2"],
    ["Phenotypic", "All Tall", "3 Tall : 1 Dwarf (3:1)"],
    ["Genotypic", "All Tt", "1 TT : 2 Tt : 1 tt (1:2:1)"],
]
story.append(make_table(ratios_mono, col_widths=[4*cm, 5.5*cm, 7.5*cm], header_bg=GREEN))
story.append(spacer(4))
story.append(mnemonic('"3 for Show, 1 Below" -> phenotypic 3:1. "1-2-1 is genotype fun"'))

story.append(spacer(6))
story += h_sub("Test Cross")
for t in [
    "Cross unknown genotype with <b>homozygous recessive (tt)</b>",
    "All offspring tall -> unknown parent was TT",
    "50% tall, 50% dwarf -> unknown parent was Tt",
]:
    story.append(bullet(t))

story.append(spacer(6))
story += h_sub("Law 3 - Law of Independent Assortment")
story.append(body('<i>"When two or more pairs of characters are inherited together, the segregation of one pair is independent of the segregation of the other pair."</i>'))
story.append(spacer(4))
story += h_sub("Dihybrid Cross: RRYY x rryy")

di_table = punnett_table(
    col_headers=["RY", "Ry", "rY", "ry"],
    row_headers=["RY", "Ry", "rY", "ry"],
    cells=[
        ["RRYY", "RRYy", "RrYY", "RrYy"],
        ["RRYy", "RRyy", "RrYy", "Rryy"],
        ["RrYY", "RrYy", "rrYY", "rrYy"],
        ["RrYy", "Rryy", "rrYy", "rryy"],
    ],
)
story.append(di_table)
story.append(spacer(4))

di_ratio = [
    ["Ratio Type", "F2 Result"],
    ["Phenotypic (F2)", "9 Round Yellow : 3 Round Green : 3 Wrinkled Yellow : 1 Wrinkled Green (9:3:3:1)"],
    ["Genotypic (F2)", "1:2:1:2:4:2:1:2:1 (9 genotypic classes)"],
]
story.append(make_table(di_ratio, col_widths=[4.5*cm, 12.5*cm], header_bg=GREEN))
story.append(spacer(4))
story.append(mnemonic('"Nine Three Three One - Big Families Need Love" (9 is biggest, 1 is the loner)'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 3: DEVIATIONS
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 3: Deviations from Mendelism")

story += h_sub("3A - Incomplete Dominance")
for t in [
    "Neither allele is fully dominant",
    "Heterozygous offspring shows <b>intermediate phenotype</b>",
    "<b>Example:</b> Snapdragon (Antirrhinum) - Red (RR) x White (rr) -> Pink (Rr)",
    "F2 phenotypic ratio = <b>1:2:1</b> (same as genotypic ratio)",
]:
    story.append(bullet(t))

story.append(spacer(4))
inc_punnett = punnett_table(
    col_headers=["R", "r"],
    row_headers=["R", "r"],
    cells=[["RR (Red)", "Rr (Pink)"], ["Rr (Pink)", "rr (White)"]],
)
story.append(inc_punnett)
story.append(spacer(4))
story.append(mnemonic('"Incomplete = 1:2:1 (same as genotype ratio)"'))

story += h_sub("3B - Codominance")
for t in [
    "Both alleles express <b>simultaneously and equally</b> in heterozygous condition",
    "<b>Example:</b> ABO Blood Groups - I<super>A</super> and I<super>B</super> are codominant; i is recessive",
]:
    story.append(bullet(t))

story.append(spacer(6))
story += h_sub("3C - Multiple Alleles + ABO Blood Groups")
for t in [
    "More than two alleles for the same gene exist in a population",
    "An individual can only have 2 alleles at a time",
    "<b>Example:</b> ABO blood group - three alleles: I<super>A</super>, I<super>B</super>, i",
]:
    story.append(bullet(t))

story.append(spacer(4))
blood_data = [
    ["Blood Group (Phenotype)", "Genotype(s)", "Allele relationship"],
    ["A", "I\u1d2aI\u1d2a or I\u1d2ai", "I\u1d2a dominant over i"],
    ["B", "I\u1d2bI\u1d2b or I\u1d2bi", "I\u1d2b dominant over i"],
    ["AB", "I\u1d2aI\u1d2b", "I\u1d2a and I\u1d2b codominant"],
    ["O", "ii", "Recessive"],
]
story.append(make_table(blood_data, col_widths=[4.5*cm, 5*cm, 7.5*cm], header_bg=TEAL))
story.append(spacer(4))
story.append(mnemonic('"A = II or Ii, B = II or Ii, AB = codominant pair, O = ii (double recessive)" -> Remember O is ZERO dominant alleles'))

story.append(spacer(6))
story += h_sub("3D - Pleiotropy")
for t in [
    "<b>One gene controls MANY traits</b>",
    "<b>Example:</b> Seed texture gene in pea also affects starch synthesis",
    "<b>Human example:</b> Phenylketonuria (PKU) - affects skin colour, mental ability, urine odour",
]:
    story.append(bullet(t))
story.append(mnemonic('"PLEIOtropy = PLEnty of effects from ONE gene"'))

story += h_sub("3E - Polygenic Inheritance")
for t in [
    "<b>Many genes control one trait</b> (opposite of pleiotropy)",
    "Shows continuous variation across population",
    "<b>Example:</b> Skin colour, height in humans; grain colour in wheat",
    "More dominant alleles = more extreme phenotype",
]:
    story.append(bullet(t))
story.append(mnemonic('"PolyGENIC = Many GENES, One Trait" (Poly = many)'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 4: CHROMOSOMAL THEORY
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 4: Chromosomal Theory of Inheritance")
for t in [
    "<b>Sutton and Boveri (1902)</b> proposed chromosomes are carriers of genes",
    "Both chromosomes and Mendelian factors occur in <b>pairs</b>",
    "They separate during <b>gamete formation</b> (meiosis)",
    "Independent assortment of chromosomes = independent assortment of genes",
]:
    story.append(bullet(t))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 5: LINKAGE & CROSSING OVER
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 5: Linkage and Crossing Over")
story += h_sub("Linkage")
for t in [
    "Genes on the <b>same chromosome</b> tend to be inherited <b>together</b>",
    "They do NOT follow the law of independent assortment",
    "<b>Thomas Hunt Morgan</b> worked on <i>Drosophila melanogaster</i> (fruit fly)",
    "Fruit fly advantages: short life cycle, large offspring, many visible mutations",
]:
    story.append(bullet(t))

story += h_sub("Crossing Over")
for t in [
    "<b>Exchange of genetic material</b> between non-sister chromatids of homologous chromosomes",
    "Occurs during <b>Prophase I of Meiosis I</b>",
    "Creates <b>recombinant chromosomes</b> with new gene combinations",
    "<b>Recombination frequency</b> = (Recombinant offspring / Total offspring) x 100",
    "Used to construct <b>genetic maps / linkage maps</b>",
]:
    story.append(bullet(t))
story.append(mnemonic('"Crossing over CROSSES the barrier of linkage to CREATE recombinants"'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 6: SEX DETERMINATION
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 6: Sex Determination")

sex_data = [
    ["Organism", "Female", "Male", "Who determines sex?"],
    ["Humans", "44 + XX", "44 + XY", "Father (Y-bearing sperm)"],
    ["Birds", "ZW", "ZZ", "Mother (W-bearing egg)"],
    ["Grasshopper", "XX", "XO", "No Y chromosome"],
    ["Honey Bee", "2n (diploid)", "n (haploid)", "Parthenogenesis"],
]
story.append(make_table(sex_data, col_widths=[4*cm, 3.5*cm, 3.5*cm, 6*cm], header_bg=ORANGE))
story.append(spacer(4))
for t in [
    "In humans: <b>females are XX (homogametic)</b>, males are <b>XY (heterogametic)</b>",
    "In birds: <b>females are ZW (heterogametic)</b>, males are <b>ZZ (homogametic)</b>",
    "In honey bees: males (drones) are haploid (from unfertilized eggs); females are diploid",
]:
    story.append(bullet(t))
story.append(mnemonic('"Humans XY Father, Birds ZW Mother, Bees are Lazy (haploid males from eggs)"'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 7: SEX-LINKED INHERITANCE
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 7: Sex-Linked Inheritance")
story.append(body("Genes located on <b>sex chromosomes</b> show sex-linked inheritance. The X chromosome carries many genes; the Y chromosome carries very few."))

story += h_sub("Haemophilia (X-Linked Recessive)")
for t in [
    "Blood does not clot normally (deficiency of clotting Factor VIII or IX)",
    "Much <b>more common in males</b> (only one X chromosome)",
    "<b>Queen Victoria of England</b> was a famous carrier",
]:
    story.append(bullet(t))

story.append(spacer(4))
haemo_data = [
    ["Genotype", "Sex", "Phenotype"],
    ["X\u1d34X\u1d34", "Female", "Normal"],
    ["X\u1d34X\u02b0", "Female", "Carrier (normal phenotype)"],
    ["X\u02b0X\u02b0", "Female", "Haemophilic"],
    ["X\u1d34Y", "Male", "Normal"],
    ["X\u02b0Y", "Male", "Haemophilic"],
]
story.append(make_table(haemo_data, col_widths=[5*cm, 4*cm, 8*cm], header_bg=RED))
story.append(spacer(4))
story += h_sub("Key Cross: Carrier Female x Normal Male")
story.append(body("X<super>H</super>X<super>h</super> x X<super>H</super>Y -> offspring: X<super>H</super>X<super>H</super> (Normal female), X<super>H</super>X<super>h</super> (Carrier female), X<super>H</super>Y (Normal male), X<super>h</super>Y (Haemophilic male)"))
story.append(body("<b>25% chance of haemophilic son; 50% of sons will be haemophilic</b>"))
story.append(spacer(4))
story += h_sub("Colour Blindness (X-Linked Recessive)")
story.append(body("Same inheritance pattern as haemophilia. Inability to distinguish <b>red and green colours</b>. Males more commonly affected."))
story.append(mnemonic('"Males are MORE LIKELY to show X-linked disorders - only ONE X, no spare copy to rescue them!"'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 8: MUTATION
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 8: Mutation")
story.append(body("<b>Mutation</b> = A sudden, heritable change in the genetic material (DNA sequence or chromosome number/structure)"))
story.append(spacer(4))
story += h_sub("Types of Mutations")

mut_data = [
    ["Type", "Description", "Example"],
    ["Point / Gene Mutation", "Change in a single base pair of DNA", "Sickle Cell Anaemia: GAG -> GUG (Glu -> Val)"],
    ["Chromosomal Aberration", "Changes in chromosome structure (deletion, duplication, inversion, translocation)", "Various cancers, Down Syndrome"],
    ["Aneuploidy - Trisomy", "2n+1: one extra chromosome", "Down Syndrome (Trisomy 21)"],
    ["Aneuploidy - Monosomy", "2n-1: one chromosome missing", "Turner's Syndrome (45, X)"],
]
story.append(make_table(mut_data, col_widths=[4*cm, 7*cm, 6*cm], header_bg=PURPLE))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 9: PEDIGREE ANALYSIS
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 9: Pedigree Analysis")
story.append(body("A <b>diagrammatic representation</b> of inheritance of a trait across generations in a family. Used to determine inheritance pattern of a trait."))
story.append(spacer(4))

symbols_data = [
    ["Symbol", "Meaning"],
    ["Circle (O)", "Normal female"],
    ["Square ([])", "Normal male"],
    ["Filled circle", "Affected female"],
    ["Filled square", "Affected male"],
    ["Half-filled circle/square", "Carrier female / Carrier male"],
    ["Horizontal line (=)", "Mating / Marriage"],
    ["Vertical line", "Offspring"],
]
story.append(make_table(symbols_data, col_widths=[5*cm, 12*cm], header_bg=TEAL))
story.append(spacer(4))

story += h_sub("Determining Inheritance Pattern")
pattern_data = [
    ["Observation", "Conclusion"],
    ["Trait skips generations", "Recessive"],
    ["Trait in every generation", "Dominant"],
    ["Only males affected", "X-linked recessive likely"],
    ["Affected father has affected sons", "Autosomal (not X-linked)"],
    ["Carrier mothers pass to sons", "X-linked recessive"],
]
story.append(make_table(pattern_data, col_widths=[9*cm, 8*cm], header_bg=GREEN))
story.append(mnemonic('"SKIP = Recessive, EVERY GEN = Dominant, ONLY MALES = X-linked"'))

# ═══════════════════════════════════════════════════════════════════
# TOPIC 10: GENETIC DISORDERS
# ═══════════════════════════════════════════════════════════════════
story += h_topic("TOPIC 10: Genetic Disorders")

story += h_sub("A. Chromosomal Disorders")
story.append(spacer(3))

chrom_data = [
    ["Feature", "Down Syndrome", "Klinefelter's Syndrome", "Turner's Syndrome"],
    ["Chromosome No.", "47 (Trisomy 21)", "47 (XXY)", "45 (XO)"],
    ["Type", "Autosomal trisomy", "Sex chromosome", "Sex chromosome monosomy"],
    ["Sex", "Male / Female", "Male", "Female"],
    ["Key Features", "Mental retardation, short stature, furrowed tongue, broad palm", "Gynaecomastia, sterile", "Webbed neck, short, rudimentary ovaries, sterile"],
    ["Fertility", "Reduced", "Sterile", "Sterile"],
    ["Extra Notes", "Risk increases with maternal age", "Develops breasts (male)", "No secondary sexual characters"],
]
story.append(make_table(chrom_data, col_widths=[3.5*cm, 4.5*cm, 4.5*cm, 4.5*cm], header_bg=ORANGE, font_size=8))
story.append(spacer(4))
story.append(mnemonic('"Down\'s goes to 21 (Trisomy 21), Kline has EXTRA X makes male BREASTS, Turner has ONLY ONE X with webbed neck"'))

story.append(spacer(6))
story += h_sub("B. Mendelian / Gene Disorders")
story.append(spacer(3))

gene_data = [
    ["Disorder", "Inheritance", "Cause", "Key Feature"],
    ["Sickle Cell Anaemia", "Autosomal Recessive", "GAG->GUG mutation in beta-globin gene; Glu->Val; HbS forms fibres", "Sickle-shaped RBCs; carriers resistant to malaria"],
    ["Phenylketonuria (PKU)", "Autosomal Recessive", "Deficiency of phenylalanine hydroxylase; Phe accumulates", "Mental retardation, light skin, musty odour (pleiotropy example)"],
    ["Thalassemia", "Autosomal Recessive", "Reduced synthesis of alpha or beta globin chains (NOT structural change)", "Anaemia; quantitative deficiency of Hb chains"],
]
story.append(make_table(gene_data, col_widths=[3.5*cm, 3.5*cm, 6*cm, 4*cm], header_bg=RED, font_size=8))
story.append(spacer(4))
story.append(note("Key distinction: Sickle Cell = STRUCTURAL change in Hb (wrong amino acid); Thalassemia = QUANTITATIVE reduction (less Hb made)"))
story.append(mnemonic('"SiPhThal" - Si(ckle cell), Ph(enylketonuria), Thal(assemia) - ALL autosomal recessive!'))

# ═══════════════════════════════════════════════════════════════════
# MASTER RATIO SUMMARY
# ═══════════════════════════════════════════════════════════════════
story += h_chapter("MASTER RATIO QUICK REFERENCE")
story.append(spacer(4))

ratio_data = [
    ["Cross Type", "F2 Phenotypic Ratio", "F2 Genotypic Ratio"],
    ["Monohybrid", "3:1", "1:2:1"],
    ["Dihybrid", "9:3:3:1", "1:2:1:2:4:2:1:2:1"],
    ["Incomplete Dominance", "1:2:1", "1:2:1"],
    ["Test Cross (Tt x tt)", "1:1", "1:1"],
    ["Codominance (AB blood)", "Equal expression of both alleles", "I\u1d2aI\u1d2b"],
]
story.append(make_table(ratio_data, col_widths=[5*cm, 7*cm, 5*cm], header_bg=DARK_BLUE))
story.append(spacer(4))
story.append(mnemonic('"Mono is 3:1 | Di is 9:3:3:1 | Incomplete flips to 1:2:1 | Test gives 1:1" - say it like a chant!'))

story.append(PageBreak())

# ═══════════════════════════════════════════════════════════════════
# MCQs
# ═══════════════════════════════════════════════════════════════════
story += h_chapter("3 CHALLENGING MCQs - Test Your Recall!")
story.append(spacer(6))

story.append(Paragraph("Attempt all questions before checking the answer key at the bottom.", note_style))
story.append(spacer(8))

# Q1
story.append(Paragraph("Q1. In a cross between a carrier female for haemophilia (X<super>H</super>X<super>h</super>) and a normal male (X<super>H</super>Y), what is the probability that a SON born will have haemophilia?", mcq_q_style))
for opt in ["(A) 25%", "(B) 50%", "(C) 100%", "(D) 0%"]:
    story.append(Paragraph(opt, mcq_opt_style))
story.append(spacer(8))

# Q2
story.append(Paragraph("Q2. A man with blood group A (genotype I<super>A</super>i) marries a woman with blood group B (genotype I<super>B</super>i). Which of the following blood groups is NOT possible in their children?", mcq_q_style))
for opt in ["(A) Blood group A", "(B) Blood group O", "(C) Blood group AB", "(D) All of the above are possible"]:
    story.append(Paragraph(opt, mcq_opt_style))
story.append(spacer(8))

# Q3
story.append(Paragraph("Q3. In snapdragon (Antirrhinum), a red-flowered plant (RR) is crossed with a white-flowered plant (rr). The F1 plants (Rr) are self-pollinated. What will be the phenotypic ratio in F2?", mcq_q_style))
for opt in ["(A) 3 Red : 1 White", "(B) 1 Red : 2 Pink : 1 White", "(C) 1 Red : 1 White", "(D) All Red"]:
    story.append(Paragraph(opt, mcq_opt_style))

story.append(spacer(30))
story.append(HRFlowable(width="100%", thickness=1, color=DARK_BLUE))
story.append(spacer(10))
story.append(Paragraph("ANSWER KEY", make_style("AKH", fontSize=11, fontName="Helvetica-Bold", textColor=DARK_BLUE)))
story.append(spacer(6))

ans_data = [
    ["Q", "Answer", "Explanation"],
    ["1", "B - 50%", "Cross: X\u1d34X\u02b0 x X\u1d34Y gives X\u1d34X\u1d34, X\u1d34X\u02b0, X\u1d34Y, X\u02b0Y. Among sons (X\u1d34Y and X\u02b0Y), 1 in 2 = 50% are haemophilic."],
    ["2", "D - All possible", "I\u1d2ai x I\u1d2bi gives I\u1d2aI\u1d2b (AB), I\u1d2ai (A), I\u1d2bi (B), ii (O). All 4 blood groups are possible. Classic trap!"],
    ["3", "B - 1:2:1", "Incomplete dominance. F2 = 1 RR (Red) : 2 Rr (Pink) : 1 rr (White). Phenotypic ratio = genotypic ratio = 1:2:1."],
]
story.append(make_table(ans_data, col_widths=[1*cm, 3.5*cm, 12.5*cm], header_bg=GREEN))

story.append(spacer(16))
story.append(Paragraph("Pro Tip for Boards: Punnett squares, chromosomal disorder tables, and blood group crosses are very high yield. Practice drawing the 4x4 dihybrid Punnett square from memory!", note_style))
story.append(spacer(6))
story.append(Paragraph("- Notes compiled as per NCERT Class 12 Biology Chapter 4 | CBSE 2026-27 -",
    make_style("Footer", fontSize=8, fontName="Helvetica-Oblique", textColor=colors.grey, alignment=TA_CENTER)))

# ── Build doc ─────────────────────────────────────────────────────────────────
doc = SimpleDocTemplate(
    OUTPUT,
    pagesize=A4,
    rightMargin=1.8*cm, leftMargin=1.8*cm,
    topMargin=2*cm, bottomMargin=2*cm,
    title="Ch4 Principles of Inheritance and Variation - NCERT Class 12",
    author="Orris Biology Tutor",
)
doc.build(story)
print("PDF created:", OUTPUT)

python /home/daytona/workspace/bio-ch4-notes/generate_pdf.py 2>&1

ls -lh /home/daytona/workspace/bio-ch4-notes/