A farmer cultivates a unique species of tomato plants. The two traits selected for breeding were the colour of the fruits and the height of the plants. The farmer initially crosses a homozygous tall plant bearing red fruits (TTRR) with a dwarf plant bearing yellow fruits (ttrr), and the genotype of all the offsprings of the F1 generation was TtRr. Next, he crosses two F1 generation plants (TtRr).
State Mendel’s Law of Independent Assortment.
Topic: Mendel’s Law of Independent Assortment
Answer
MENDEL’S LAW OF INDEPENDENT ASSORTMENT states that when two or more pairs of contrasting characters are considered together, the alleles of one pair segregate and are inherited INDEPENDENTLY of the alleles of the other pair.
The essential word is INDEPENDENTLY — one character is inherited without reference to the other.
THE EVIDENCE is in part (b) of this very question. If height and colour were linked, the F2 generation could only produce the parental combinations — tall-red and dwarf-yellow. The appearance of TALL-YELLOW and DWARF-RED plants proves the two characters assorted independently, and the 9:3:3:1 ratio is the numerical expression of that.
Mendel’s three laws, worth knowing as a set: LAW OF DOMINANCE — in a hybrid, only the dominant character is expressed LAW OF SEGREGATION — the two alleles of a pair separate during gamete formation, each gamete receiving only one LAW OF INDEPENDENT ASSORTMENT — different pairs of alleles are inherited independently of one another