Three pairs of genes with two alleles each A1 and A2, B1 and B2, and C1 and C2 control the height of a plant. The alleles of these genes have an additive relationship: each copy of alleles A1, B1, and C 1 contributes 6 cm to plant height, and each copy of alleles A 2, B2, and C2 contributes 3 cm.

A) What is the expected height of plants with the homozygous genotype A1B1C1? (answer is not 18cm - can someone show me how to work this)

B) What is the expected height of plants with the homozygous genotype A2B2C2?

C) What height is expected in the F1 progeny of a cross between A1 A1 B1 B1C1 C1 and A2 A2 B2 B2 C2 C2?

D) What is the expected height of a plant with the genotype A1 A2 B2 B2C1 C2?

E) Identify all possible genotypes for plants with an expected height of 33 cm

Ans A) Plant height is 6+6+6+6+6+6 = 36cm

Ans B) Plant height is 3+3+3+3+3+3 = 18cm

Ans C) Plant height is 6+3+6+3+6+3 = 27cm

Ans D) Plant height becomes 6+3+3+3+6+3 = 24cm

Ans E) A1A1B1B1C1C2 = 6+6+6+6+6+3 = 33cm

A1A1B1B2C1C1 = 6+6+6+3+6+6 = 33cm

A1A2B1B1C1C1 = 6+3+6+6+6+6 = 33cm

Explanation:

Three pairs of genes with two alleles each A1 and A2, B1 and B2, and C1 and C2 control the height of a plant. The alleles of these genes have an additive relationship:

This Statement means every allele contribute the height by simple addition.

Each copy of alleles A1, B1, and C 1 contributes 6 cm to plant height.

Each copy of alleles A 2, B2, and C2 contributes 3 cm to plant height.

A) Expected height of plants with the homozygous genotype A1B1C1.

Ans 1) Recall the term Homozygous which means that its both alleles are of same type so homozygous genotype becomes A1A1B1B1C1C1.

Plant height is 6+6+6+6+6+6 = 36cm

B) Expected height of plants with the homozygous genotype A2B2C2.

Ans 2) homozygous genotype becomes A2A2B2B2C2C2.

Plant height is 3+3+3+3+3+3 = 18cm

C) Expected height in the F1 progeny of a cross between A1 A1 B1 B1C1 C1 and A2 A2 B2 B2 C2 C2.

Ans 3) A1 A1 B1 B1C1 C1 and A2 A2 B2 B2 C2 C2

Gametes formation results in half alleles. so

A1B1C1 X A2B2C2

F1 generation become A1A2B1B2C1C2

Plant height is 6+3+6+3+6+3 = 27cm

D) Expected height of a plant with the genotype A1 A2 B2 B2C1 C2?

Ans 4) Plant height becomes 6+3+3+3+6+3 = 24cm

E) Identify all possible genotypes for plants with an expected height of 33 cm

Ans 5) A1A1B1B1C1C2 = 6+6+6+6+6+3 = 33cm

A1A1B1B2C1C1 = 6+6+6+3+6+6 = 33cm

A1A2B1B1C1C1 = 6+3+6+6+6+6 = 33cm