• 38 questions

Monohybrid Cross Quiz

Pick the ratio a cross gives and see the four combinations behind it.

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Which cross is expected to give 3 offspring with the dominant trait for every 1 with the recessive trait?

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Unofficial practice questions, not affiliated with any school, exam board or textbook publisher. Bank checked October 8, 2026.

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All 38 questions with answers

Ratios from a cross 20

  • A heterozygous tall plant (Tt) is crossed with a short plant (tt). What ratio of tall to short offspring is expected? Answer: 1 : 1. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • A tall plant is crossed with a short plant (tt). About half of the offspring are tall and half are short. What is the genotype of the tall parent? Answer: Tt. Source: Wikipedia, Test cross. Read 2026-10-08.
  • A tall plant of unknown genotype is crossed with a short plant (tt). All of the many offspring are tall. What is the tall parent most likely to be? Answer: TT. Source: Wikipedia, Test cross. Read 2026-10-08.
  • A Tt × Tt cross has already given three tall offspring. What is the chance that the next one is short? Answer: 1 in 4. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • The cross Rr × Rr gives 400 seeds. Round (R) is dominant over wrinkled (r). About how many seeds are expected to be wrinkled? Answer: 100. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • The cross Tt × tt gives 60 offspring. Tall (T) is dominant. About how many are expected to be tall? Answer: 30. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
Show all 38 questions (32 more)

Ratios from a cross, continued

  • In a plant, purple flowers (P) are dominant over white flowers (p). In the cross Pp × pp, what percent of the offspring is expected to have white flowers? Answer: 50%. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • In a plant, tall (T) is dominant over short (t). What do the offspring of the cross TT × tt look like? Answer: All tall. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • In pea plants, round seeds (R) are dominant over wrinkled seeds (r). A pure-breeding round plant (RR) is crossed with a wrinkled plant (rr). What genotype do the offspring have? Answer: All Rr. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • In the cross Pp × Pp, what percent of the offspring is expected to be heterozygous (Pp)? Answer: 50%. Source: Wikipedia, Punnett square. Read 2026-10-08.
  • In the cross Rr × Rr, what fraction of the round seeds is expected to be heterozygous (Rr)? Answer: 2/3. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Purple (P) is dominant over white (p). In the cross PP × Pp, what fraction of the offspring is expected to have white flowers? Answer: None. Source: Wikipedia, Punnett square. Read 2026-10-08.
  • Short is the recessive trait, so a short plant is tt. What do the offspring of two short plants look like? Answer: All short. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Tall (T) is dominant over short (t). In the cross Tt × Tt, what fraction of the offspring is expected to be short? Answer: 1/4. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Two heterozygous plants are crossed: Tt × Tt. What is the expected ratio of the genotypes TT : Tt : tt? Answer: 1 : 2 : 1. Source: Wikipedia, Punnett square. Read 2026-10-08.
  • Two Rr pea plants are crossed. Round (R) is dominant over wrinkled (r). What ratio of round to wrinkled seeds is expected? Answer: 3 : 1. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Two tall plants are crossed, and about a quarter of their offspring are short. Tall (T) is dominant. What are the genotypes of the parents? Answer: Tt and Tt. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Which cross gives offspring that are all heterozygous? Answer: TT × tt. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Which cross is expected to give 3 offspring with the dominant trait for every 1 with the recessive trait? Answer: Tt × Tt. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • Which genotypes are expected among the offspring of the cross PP × Pp? Answer: Half PP and half Pp. Source: Wikipedia, Punnett square. Read 2026-10-08.

Genetics words 18

  • A plant has the genotype Tt, and tall (T) is dominant over short (t). How does the plant look? Answer: Tall. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance. Read 2026-10-08.
  • An organism with two different alleles of a gene, such as Tt, is called… Answer: Heterozygous. Source: National Human Genome Research Institute, Talking Glossary: Heterozygous. Read 2026-10-08.
  • An organism with two identical alleles of a gene, such as TT or tt, is called… Answer: Homozygous. Source: National Human Genome Research Institute, Talking Glossary: Homozygous. Read 2026-10-08.
  • How is the F2 generation made in a monohybrid cross? Answer: By crossing F1 plants with each other, or letting them self-pollinate. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • In a cross written with letters, what does a capital letter such as T stand for? Answer: The dominant allele. Source: Wikipedia, Punnett square. Read 2026-10-08.
  • Round (R) is dominant over wrinkled (r). Which of these is a phenotype? Answer: Wrinkled seeds. Source: National Human Genome Research Institute, Talking Glossary: Phenotype. Read 2026-10-08.
  • What does a monohybrid cross follow? Answer: One trait, controlled by one gene. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance. Read 2026-10-08.
  • What does the principle of segregation say? Answer: The two alleles of a gene separate, so each gamete carries only one. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance. Read 2026-10-08.
  • What is a genotype? Answer: The alleles an organism has, written with letters such as Tt. Source: National Human Genome Research Institute, Talking Glossary: Genotype. Read 2026-10-08.
  • What is a phenotype? Answer: A trait that can be observed, such as tall or short. Source: National Human Genome Research Institute, Talking Glossary: Phenotype. Read 2026-10-08.
  • What is a pure-breeding (true-breeding) plant? Answer: A homozygous plant: its self-pollinated offspring keep the same trait. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance. Read 2026-10-08.
  • What is a test cross? Answer: A cross with a homozygous recessive organism, to find out a hidden genotype. Source: Wikipedia, Test cross. Read 2026-10-08.
  • What is an allele? Answer: One of the versions of a gene. Source: National Human Genome Research Institute, Talking Glossary: Allele. Read 2026-10-08.
  • What is the F1 generation? Answer: The offspring of the two parent plants. Source: Wikipedia, Monohybrid cross. Read 2026-10-08.
  • When does a recessive trait show? Answer: Only when both alleles are the recessive one. Source: National Human Genome Research Institute, Talking Glossary: Recessive. Read 2026-10-08.
  • Which describes a dominant allele? Answer: It shows in the organism even when only one copy is present. Source: National Human Genome Research Institute, Talking Glossary: Dominant. Read 2026-10-08.
  • Which gametes can a Tt plant make? Answer: T and t, in equal numbers. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance. Read 2026-10-08.
  • Who worked out these ratios by crossing pea plants? Answer: Gregor Mendel. Source: Nature Education, Scitable: Gregor Mendel and the Principles of Inheritance; Wikipedia, Punnett square. Read 2026-10-08.

How this list was compiled: Questions, wrong choices and explanations were written for this site. Each definition and rule was checked on the page named in the question's source line: the National Human Genome Research Institute Talking Glossary (Allele, Dominant, Recessive, Homozygous, Heterozygous, Genotype, Phenotype), https://www.genome.gov/genetics-glossary; Nature Education, Scitable, Gregor Mendel and the Principles of Inheritance; and Wikipedia (Monohybrid cross, Punnett square, Test cross). All read 2026-10-08. Every ratio, fraction, percent and count was worked out from the four combinations of the cross and checked again. Licence: own work

How it works

This monohybrid cross quiz has 38 questions in two sets: the offspring ratios of crosses such as Tt × Tt and Tt × tt, and the words behind them, from allele and genotype to test cross.

Read the full guide

Two sets

Ratios from a cross gives the parents' genotypes and asks for the expected offspring as a ratio, a fraction, a percent or a count, and works parents back from their offspring. Genetics words adds dominant, recessive, homozygous, heterozygous, phenotype, F1 and F2.

One gene at a time

A monohybrid quiz keeps to one gene with two alleles, a capital letter for the dominant one. The traits are seed shape, height and flower color in plants. Crosses of two genes at once are left out.

  • Write the four combinations first: each parent gives one of its two letters to each offspring.
  • Each offspring is a fresh draw: after three tall plants from Tt × Tt, the chance of a short one is still 1 in 4.

Questions and answers

What is a monohybrid cross?

A cross that follows one trait controlled by one gene. In the classic case two pure-breeding parents, TT and tt, give offspring that are all Tt, and crossing those offspring gives the next generation in a 3 : 1 ratio.

What is the phenotypic ratio of a monohybrid cross?

For two heterozygous parents, Tt × Tt, three offspring are expected to show the dominant trait for every one that shows the recessive trait: 3 : 1. For Tt × tt the expected ratio is 1 : 1.

What is the genotypic ratio of a monohybrid cross?

For Tt × Tt it is 1 TT : 2 Tt : 1 tt. One quarter of the offspring are expected to be homozygous dominant, half heterozygous and one quarter homozygous recessive.

What is the difference between a monohybrid and a dihybrid cross?

A monohybrid cross follows one trait, such as seed shape. A dihybrid cross follows two at once, such as seed shape and seed color, and parents heterozygous for both give four kinds of offspring in a 9 : 3 : 3 : 1 ratio.

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