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2020Q7(a)(iv)Genetics – Some Basic Fundamentals
DefinitionModerate1 mark
7(a)

A homozygous dominant tall pea plant bearing red flowers (TTRR) is crossed with a homozygous recessive dwarf pea plant bearing white flowers (ttrr).

State Mendel’s Law of Independent Assortment.

Topic: Law of Independent Assortment

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Answer

Exam 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.

Explanation

The essential word is INDEPENDENTLY — one character is inherited without reference to the other.

THE EVIDENCE is in part (iii) of this very question. If height and flower colour were linked, the F2 generation could produce only the parental combinations — tall-red and dwarf-white. The appearance of TALL-WHITE and DWARF-RED plants proves the two characters assorted independently, and 9:3:3:1 is the numerical expression of it.

Mendel’s three laws: DOMINANCE (only the dominant shows in a hybrid), SEGREGATION (the two alleles of a pair separate into different gametes), INDEPENDENT ASSORTMENT (different pairs are inherited independently).

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