Maharashtra State Board · Class 12 · All chapters

Biology — Complete Formula Sheet

Board Formulas

52 formulas · 5 chapters

Ch 1 · Reproduction in Lower and Higher Plants

1.Double Fertilisation★
$Syngamy: male gamete + egg \to zygote (2n); Triple fusion: male gamete + 2 polar nuclei \to PEN (3n)$
Discovered by S.G. Nawaschin in Lilium and Fritillaria. Two male gametes take part; hence 'double'.
2.Types of Ovules (Placentation)
$Orthotropous, Anatropous, Campylotropous, Amphitropous, Hemitropous, Circinotropous$
Orientation of micropyle relative to funicle and chalaza. Anatropous is the commonest form (in most angiosperms).
3.Types of Pollination★
$Autogamy (same flower); Geitonogamy (same plant); Xenogamy (different plant)$
Autogamy and geitonogamy are genetically self-pollination; xenogamy is cross-pollination.
4.Pollen–Pistil Interaction
$Pollen germination \to tube growth \to entry into ovule \to fertilisation$
Regulated by chemical (γ-aminobutyric acid, Ca²⁺) and self-incompatibility genes.
5.Endosperm Development★
$PEN (3n) \to Nuclear \to Cellular \to Helobial$
Three types of endosperm development. Coconut water is nuclear endosperm.
6.Embryo Development in Dicot★
$Proembryo \to Globular \to Heart-shaped \to Torpedo \to Mature$
Follows Onagrad type in Capsella bursa-pastoris (Balbharati standard example).
7.Post-fertilisation Changes
$Ovule \to Seed; Ovary \to Fruit; Ovule wall \to Seed coat$
Petals, stamens, style, stigma wither. Sepals may persist (e.g. tomato).
8.Vegetative Propagation Structures★
$Runner, Sucker, Offset, Bulbil, Rhizome, Corm, Tuber, Leaf buds$
Balbharati lists 8 forms — memorise with one example each.
9.Apomixis
$Seed formation without fertilisation$
Diploid embryo from nucellus/integument. Example: Citrus, Mango. Used in hybrid crop production.
10.Polyembryony
$Two or more embryos in a single ovule/seed$
Example: Citrus, Mango. Common in gymnosperms too.

Ch 3 · Genetics and Evolution

1.Monohybrid Cross Ratio★
$A a \times A a \to 1 AA : 2 A a : 1 aa (genotypic) = 3 : 1 (phenotypic)$
Basis of Mendel's law of segregation. Complete dominance assumed.
2.Dihybrid Cross Ratio★
$9 A_B_ : 3 A_bb : 3 aaB_ : 1 aabb$
Independent assortment of two genes on different chromosomes.
3.Test Cross★
$A a \times aa \to 1 A a : 1 aa$
Cross with homozygous recessive to determine genotype of the unknown.
4.Incomplete Dominance
$R R \times r r \to R r (intermediate phenotype)$
Neither allele fully dominant. Example: Mirabilis jalapa (4 o'clock plant).
5.Codominance
$I^{A} I^{B} \to AB blood group$
Both alleles fully expressed. ABO blood group in humans.
6.Multiple Alleles — ABO Blood Group★
$I^{A}, I^{B}, i; I^{A} = I^{B} > i$
Three alleles at one locus. Six genotypes; four phenotypes (A, B, AB, O).
7.Chromosomal Sex Determination★
$XY: mammals; XO: grasshopper; ZW: birds; ZO: moth$
In XY and XO systems, male is heterogametic. In ZW and ZO, female is heterogametic.
8.Sex-Linked Inheritance
$X-linked recessive: haemophilia, colour blindness$
Affects males more (only one X). Females can be carriers.
9.Hardy–Weinberg Equation★
$p^{2} + 2 pq + q^{2} = 1, p + q = 1$
Genotype frequencies in a stable population. Conditions: no mutation, no selection, no migration, random mating, large population.
10.Linkage Frequency
$Recombination frequency (RF) = \frac{recombinants}{total offspring} \times 100$
Used in gene mapping. 1% RF = 1 map unit (cM).
11.Pleiotropy
$One gene \to multiple phenotypic effects$
Example: sickle cell anaemia; phenylketonuria.

Ch 4 · Molecular Basis of Inheritance

1.Chargaff's Rule★
$% A = % T, % G = % C, A + G = T + C$
Empirical base-pair rule preceding Watson–Crick model. Purines = pyrimidines.
2.Watson–Crick Structure Parameters★
$Diameter = 2 nm; Rise/bp = 0.34 nm; Pitch = 3.4 nm; 10 bp/turn$
Right-handed double helix. Antiparallel strands with major and minor grooves.
3.Base Pairing★
$A = T (2 H-bonds), G \equiv C (3 H-bonds)$
Purine (A, G) pairs with pyrimidine (T, C). GC-rich regions are more stable.
4.DNA Length Calculation
$Length = No. of bp \times 0.34 nm$
Human genome ≈ 6.6 × 10⁹ bp ≈ 2.2 m long DNA.
5.Semi-conservative Replication★
$Each daughter DNA = 1 parental strand + 1 new strand$
Verified by Meselson–Stahl experiment (1958) using ¹⁵N/¹⁴N.
6.Central Dogma★
$DNA replication DNA transcription RNA translation Protein$
Proposed by Crick. Reverse transcription (RNA → DNA) exists in retroviruses.
7.Codon and Anticodon
$Codon: mRNA triplet; Anticodon: tRNA triplet complementary to codon$
64 codons; 61 code for 20 amino acids; 3 stop codons (UAA, UAG, UGA).
8.Genetic Code Properties★
$Triplet, degenerate, universal, non-overlapping, comma-less$
Balbharati lists all five properties — memorise as a bullet list.
9.Lac Operon Components★
$i \to repressor, P, O \to control, z, y, a \to structural genes$
Regulated by lactose (inducer). Model of prokaryotic gene regulation.
10.Start and Stop Codons
$Start: AUG (Met); Stop: UAA, UAG, UGA$
AUG codes for Methionine (Met) and initiates translation. Stop codons do not code for any amino acid.
11.Enzymes in Replication
$Helicase, Primase, DNA polymerase, Ligase, Topoisomerase$
DNA polymerase reads 3' to 5'; synthesises new strand 5' to 3'.

Ch 10 · Human Health and Diseases

1.Types of Immunity★
$Innate (nonspecific) vs Acquired (specific)$
Innate present from birth; acquired develops after antigen exposure.
2.Active vs Passive Immunity★
$Active: body makes antibodies (vaccine, infection); Passive: preformed antibodies given (colostrum, ATS)$
Active is slow but long-lasting. Passive is quick but temporary.
3.Types of Acquired Immunity★
$Humoral (antibody-mediated, B-cells) + Cell-mediated (T-cells)$
B-cells make antibodies. T-cells attack infected cells directly.
4.Immunoglobulin Types
$IgG, IgA, IgM, IgD, IgE$
IgG most abundant (~75%). IgE is involved in allergic responses. IgM: first line.
5.Antibody Structure★
$Y-shaped, 2 heavy chains (H₂) + 2 light chains (L₂), 2 antigen-binding sites$
H₂L₂ formula. Disulfide bonds hold the chains. Fab region binds antigen; Fc binds effector.
6.HIV Structure and Type★
$Retrovirus with RNA + reverse transcriptase; targets CD4+ T-cells$
Causes AIDS. Discovered by Luc Montagnier and Robert Gallo. Transmitted by blood, sexual contact, mother to child.
7.Cancer Types★
$Carcinoma (epithelial), Sarcoma (connective), Leukaemia (blood), Lymphoma (lymphoid)$
80% of human cancers are carcinomas. Blood cancer = leukaemia.
8.Metastasis
$Cancer cells detach and migrate to distant organs via blood/lymph$
The most dangerous property of malignant tumours.
9.Common Diseases and Pathogens (Balbharati list)
$Typhoid: S a l m o n e l l a, Pneumonia: S t r e pt ococc u s, Malaria: P l a s m o d i u m$
Also: Ascariasis (Ascaris), Filariasis (Wuchereria), Ringworm (Microsporum).
10.Drugs of Abuse
$Opioids: heroin (Papaver); Cannabinoids: cannabis; Cocaine: coca$
Drug source plants — Balbharati specific 2-mark question.

Ch 12 · Biotechnology

1.Steps of rDNA Technology★
$1) Isolation \to 2) Cutting \to 3) Amplification/Ligation \to 4) Transformation \to 5) Selection$
Five sequential steps. Balbharati asks each with a specific example.
2.Restriction Endonuclease Cutting★
$EcoRI: 5’-GAATTC-3’ \to 5’-G + AATTC-3’; makes sticky ends$
Palindromic recognition site (6 bp). Sticky ends allow ligation of two DNAs cut with same enzyme.
3.Vector Requirements
$ori, selectable marker, cloning sites, small size$
pBR322 has ori, ampR, tetR, and multiple cloning sites.
4.PCR Amplification Cycle★
$Denaturation (94°C) \to Annealing (55°C) \to Extension (72°C)$
One cycle doubles DNA (2ⁿ amplification after n cycles). Uses Taq polymerase.
5.PCR Amplification Formula
$N = N_{0} \times 2^{n}$
n = number of cycles. Starting from 1 molecule, after 30 cycles ≈ 10⁹ molecules.
6.Bt Toxin Gene★
$cry1Ac gene from Bacillus thuringiensis \to Bt cotton (bollworm resistance)$
Cry protein activated in alkaline gut of insect. Non-toxic to mammals.
7.Golden Rice
$psy gene (daffodil) + crtI (bacteria) \to β-carotene in endosperm$
β-carotene is a precursor of vitamin A. Combats vitamin A deficiency.
8.Recombinant Insulin★
$Human insulin gene \to E . co l i \to humulin$
First rDNA therapeutic (Eli Lilly, 1982). Chains A and B produced separately and joined.
9.Transgenic Animals
$Rosie (transgenic cow) — produces human α-lactalbumin in milk$
First transgenic mammal producing human protein in milk.
10.Gel Electrophoresis
$DNA fragments separated by size in agarose gel under electric field$
Smaller fragments move faster. Visualised with ethidium bromide under UV light.