Some ratios to remember

• Dihybrid ratio: 9:3:3:1
• Duplicate gene action; 15:1
• Complementary gene: 9:7
• Modifying / Supplementary : 9:3:4
• Inhibitory:13:3
• Masking : 12:3:1
• Polymeric : 9:6:1
• Additive: 1:4:6:4:1

Characters of mutation

a) Recessive

b) Harmful effects

c) Recurrent

d) Rate of forward mutation is higher than reverse mutation

e) Mutation alleles are pleiotropic

Form

• DNA à Double stranded usually in B form
• RNA à Double stranded usually in A form