Question

1)Wild-type snapdragon plants have green leaves.

Gardeners discovered and bred a new variety of the snapdragon plant that had golden leaves rather than green leaves. A cross between two golden snapdragons produced two types of progeny, some with golden leaves and some with green leaves, in a 2:1 ratio.

This phenotype ratio is typical of:

Group of answer choices

Incomplete dominance

Complementation

Maternal effect

Recessive lethality

2)Wild-type plants of the squash family synthesize a bitter chemical, cucurbitacin, that is toxic.

Through selective breeding, gardeners created squash varieties that are edible; these carry mutations in the enzymes needed to synthesize cucurbitacin. However, cross-pollination between different varieties with mutations in different genes produces progeny that are toxic!

This is an example of:

Group of answer choices

1-Maternal effect

2-Complementation

3-Recessive lethality

4-Incomplete penetrance

Answer 1

1) when two plants with golden leaves have crossed the progenies include plants with green leaves so golden leaves is dominant to green leaves, and golden leaves is homozygous lethal.

let the alleles be G- golden, g- green

Gg- golden gg- green GG- lethal

Gg * Gg

	G	g
G	GG ( lethal)	Gg ( golden)
g	Gg (golden)	gg ( green)

the phenotypic ratio is

Golden: green=2:1

d) recessive lethal.

Incomplete dominance- heterozygotes show an intermediate phenotype compared to homozygotes.

Complementation- functional copies of two genes are required to produce the normal phenotype.

Maternal effect- phenotype of the progeny depends on the genotype of the mother.

Recessive lethality- lethal in homozygous condition.

2) two genes are involved in the production of toxin and functional copies of both genes are required to produce toxin.

let the genes be A and B and the alleles of the genes be A- functional allele, a- recessive allele, B- functional allele, b- mutated allele.

varieties which does not produce toxin have genotype AAbb and aaBB

AAbb * aaBB

AaBb

so the answer is 2) complementation ( functional copy of two genes are requred to produce normal phenotype).