Q6 of 53 Page 33

What are the characteristic features of a true-breeding line?

A true breeding line is one that, having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations. It increases homozygosity of the organism. This also helps to eliminate the harmful recessive genes through deletion. Thus promoting accumulation of superior genes.


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4

How was it concluded that genes are located on chromosomes?

 5

A plant with red flowers was crossed with another plant with yellow flowers. If F1 showed all flowers orange in colour, explain the inheritance.

 7

In peas, tallness is dominant over dwarfness, and red colour of flowers is dominant over the white colour. When a tall plant bearing red flowers was pollinated with a dwarf plant bearing white flowers, the different phenotypic groups were obtained in the progeny in numbers mentioned against them:

Tall, Red = 138


Tall, White = 132


Dwarf, Red = 136


Dwarf, White = 128


Mention the genotypes of the two parents and of the four offspring types.


 8

Why is the frequency of red-green colour blindness is many times higher in males than that in the females?