Maharashtra State Board · Class 10 · Biology · Chapter 1

Heredity and Evolution — Formula Sheet

Board Formulas

6 formulas

1.Monohybrid Ratio (F₂ Generation)★
$3 : 1 (phenotype); 1 : 2 : 1 (genotype)$
Cross of two heterozygotes (Tt × Tt). 3 tall : 1 short by phenotype; 1 TT : 2 Tt : 1 tt by genotype.
2.Dihybrid Ratio (F₂)
$9 : 3 : 3 : 1$
Two independent traits. 9 both dominant : 3 one dom : 3 other dom : 1 both recessive.
3.Sex Determination in Humans★
$Father XY, Mother XX \to Offspring XX or XY$
Father's sperm determines sex — X from father → girl, Y from father → boy.
4.DNA Base Pairing
$A \equiv T, G \equiv C$
Adenine pairs with Thymine (2 H-bonds), Guanine pairs with Cytosine (3 H-bonds).
5.Gene, Chromosome, DNA★
$Gene \subset DNA \subset Chromosome$
Chromosome contains DNA, which is made up of genes (functional units).
6.Natural Selection (Darwin's Formula)
$Variation + Struggle for existence + Survival of fittest \to Evolution$
Favourable variations survive and reproduce; unfavourable die out.