Advertisements
Advertisements
Question
In a monohybrid cross of plants with red and white flowered plants, Mendel got only red-flowered plants. On self-pollinating these F1 plants got both red and white flowered plants in 3:1 ratio. Explain the basis of using RR and rr symbols to represent the genotype of plants of parental generation.
Solution
On crossing red and white flower only red colour flower appeared in the F1 generation. But the white colour flower again appear in the F2 generation which is raised out of the F1 individuals only. Mendel reasoned that there is a factor of each and every character. Accordingly, there has to be one factor (R) for red flower and other one factor (r) for white flower. In case, an organism possess only one copy of the gene then the possibility of reappearance of white flower in the F2 generation of the given cross is not there. Also the ratio (3:1 of red and white) indicates that each organism must possess two copies of a particular gene.
APPEARS IN
RELATED QUESTIONS
Differentiate between the following -
Homozygous and Heterozygous
Given below are the F2 – phenotypic ratios of two independently carried monohybrid crosses :
(i) 1 : 2 : 1
(ii) 3 : 1
Mention what does each ratio suggest.
A certain couple got four daughters in a sequence and no son. Does it mean that the husband does not produce Y-chromosome bearing sperms? Explain. What is the chance of this couple having a daughter?
Differentiate Between Monohybrid and Dihybrid cross.
Pure-bred tall pea plants are first crossed with pure-bred dwarf pea plants. The pea plants obtained in the F1 generation are then selfed to produce F2 generation of pea plants.
What is the ratio of tall plants to dwarf plants in the F2 generation?
Pure-bred tall pea plants are first crossed with pure-bred dwarf pea plants. The pea plants obtained in the F1 generation are then selfed to produce F2 generation of pea plants.
Which type of plants was missing in the F1 generation but reappeared in the F2 generation?
Cross between hybrid and recessive parent:
Assertion (A): In humans, if gene (B) is responsible for black eyes and gene (b) responsible for brown eyes, then the colour of eyes of the progeny having gene combination Bb, bb or BB will be black only.
Reason (R): The black colour of the eyes is a dominant trait.
