How was it concluded that genes are located on chromosomes?
Chromosome theory of inheritance was proposed by Sutton and Boveri independently in 1902. The theory believes that chromosomes are vehicles of heriditary information, possess Mendelian factors or genes and it is the chromosomes which segregate and assort independently during transmission from one generation to the next.
A plant with red flowers was crossed with another plant with yellow flowers. If F1 showed all flowers orange in colour, explain the inheritance.
Incomplete dominance is the phenomenon where neither of the two alleles shows dominance thus producing intermediate hybrid between the expression of two alleles in homozygous state. In this case, a new phenotype in between the two original phenotype appears.
What are the characteristic features of a true-breeding line?
True breeding is a stable trait inheritance and expression for several generations as a result of continuous self-pollination.
Characteristic features of a true-breeding line
(i) They are used as parents in artificial hybridisation as they provide gametes with all similar traits.
(ii) Homozygous recessive plants are used in test cross to determine the genotype.
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
$$ \begin{aligned} & \text { Tall, Red }=138 \\ & \text { Tall, } \text { White }=132 \\ & \text { Dwarf, Red }=136 \\ & \text { Dwarf, } \text { White }=128 \end{aligned} $$
Mention the genotypes of the two parents and of the four offspring types.
The result shows that the four types of offspring are in a ratio of $1: 1: 1: 1$. Such a result is observed in a test cross progeny of a dihybrid cross.
The cross can be represented as
Parents Tall and red $(\mathrm{TtRr}) \times$ Dwarf and white (ttrr)
Offsprings
Why is the frequency of red-green colourblindness is many times higher in males than that in the females?
Colourblindness is a X-inked sex inheritance. For becoming colourblind, the female must have the allele for it in both her X-chromosomes and if only one X-chromosome of female possess allele for colour blind character she becomes the carrier for this characteristics But males develop colourblindness when their sole X- chromosome has the allele for it. Thus males are more prone to colour blindness while females are carriers.