Working out cross ratios on paper — practice questions

Question 1 · difficulty L2 · understanding

The classic F2 phenotypic ratio for independently assorting genes with complete dominance:

• A. 1:2:1
• B. 9:3:3:1
• C. 1:1:1:1 only
• D. 3:1

Question 2 · difficulty L2 · understanding

The F2 phenotypic ratio under complete dominance:

• A. 9:3:3:1
• B. 3:1
• C. 1:2:1
• D. 1:1

Question 3 · difficulty L3 · application

A heterozygous tall pea plant, Tt, is crossed with a dwarf plant, tt. What phenotypic ratio is expected if T is completely dominant?

• A. All tall
• B. 3 tall : 1 dwarf
• C. 1 tall : 1 dwarf
• D. 1 tall : 3 dwarf

Question 4 · difficulty L3 · understanding

In a plant, black seed color $$(\mathrm{BB} / \mathrm{Bb})$$ is dominant over white seed color $$(\mathrm{bb})$$. In order to find out the genotype of the black seed plant, with which of the following genotype will you cross it?

• A. $$\mathrm{BB}$$
• B. $$\mathrm{bb}$$
• C. $$\mathrm{Bb}$$
• D. $$\mathrm{BB} / \mathrm{Bb}$$

Question 5 · difficulty L3 · understanding

A heterozygous pea plant with violet flowers was crossed with homozygous pea plant with white flower. Violet is dominant over white. Which one of the following represents the expected combinations among 40 progenies formed?

• A. 30 produced violet and 10 produced white flowers
• B. 20 produced violet and 20 produced white flowers
• C. All 40 produced violet flowers
• D. All 40 produced white flowers

Question 6 · difficulty L3 · understanding

What is the expected percentage of F 2 progeny with yellow and inflated pod in dihybrid cross experiment involving pea plants with green coloured, inflated pod and yellow coloured constricted pod?

• A. 9%
• B. 100%
• C. 56.25%
• D. 18.75%

Question 7 · difficulty L3 · understanding

The production of gametes by the parents, formation of zygotes, the F 1 and F 2 plants, can be understood from a diagram called :

• A. Net square
• B. Bullet square
• C. Punch square
• D. Punnett square

Question 8 · difficulty L3 · understanding

How many true breeding pea plant varieties did Mendel select as pairs, which were similar except in one character with contrasting traits?

• A. 14
• B. 4
• C. 2
• D. 8

Question 9 · difficulty L5 · analysis

Two pea plants with genotype RrYy are crossed, with the two gene pairs assorting independently. What is the probability of an offspring with genotype rryy?

• A. 1/4
• B. 1/16
• C. 1/8
• D. 3/16