Question

how do mendel's experiment show that traits are inherited independently depict with the help of a cross?

Answer 1

Mendel crosses varieties of pea plants that differed in more than one characters from each other by two pairs of genes. This is called dihybrid cross. By performing this cross he stated the law of independent assortment which explains that alleles of different genes are assorted independently of each other at the time of gamete formation. In monohybrid cross produces two phenotypes (3:1) whereas dihybrid cross produces four phenotypes in the ratio of 9:3:3:1. This 9:3:3:1 ratio also shows that the two different genes independently express the phenotypic ratio of 3:1 each. This proves that all the traits in an organism are inherited independently.

The cross will be
Parents Tall, Smooth seeded (TS) X Dwarf, wrinkle seeded(ts)

Gametes Ã	TS	Ts	tS	ts
TS	TTSS (tall,smooth)	TTSs (tall, smooth)	TtSS (tall, smooth)	TtSs (tall, smooth)
Ts	TTSs (tall, smooth)	TTss (tall, wrinkled)	TtSs (tall, smooth)	Ttss (tall, wrinkled)
tS	TtSS (tall, smooth)	TtSs (tall, smooth)	ttSS (dwarf, smooth)	ttSs (dwarf, smooth)
ts	TtSs (tall, smooth)	Ttss (tall, wrinkled)	ttSs (dwarf, smooth)	ttss (dwarf, wrinkled)

Here we get four different types of phenotype - 9 tall, smooth + 3 tall, wrinkled + 3 dwarfs, smooth + 1 dwarf, wrinkled. Thus the ratio will be 9:3:3:1.