Question

I’m so confused by this, please explain

Punnett Squares

Reginald Punnett was a British geneticist who developed the Punnett square to explain how the chromosomes of parents cross and produce offspring. In order to solve genetics problems using a Punnett square, it is necessary to a) understand the associated vocabulary and b) understand some of the rules for solving the problems.

· Before you continue with the problems below, review the meaning of the terms allele, dominant, recessive, homozygous, heterozygous, genotype and phenotype.

· You should also review the Punnett Square Basics video linked in the unit lesson.

In this first problem (question #3), the key and genotype of the parents will be done for you as an example. For problems #4 and #5, you will fill in those details based on the information in the question.

Remember, when asked for the genotypic ratio, it may be expressed as 25%(GG):50%(Gg):25%(gg), for example. Or, you may write it more succinctly as 1GG:2Gg:1gg. Either way will be correct.

The phenotypic ratio will use descriptive terms, for example, 3(Green):1(clear), 2(Green):2(clear), or whatever it may be depending on the results of your cross.

3. In corn plants, the allele for green kernels (G) is dominant over clear kernels (g). Cross a homozygous dominant plant with a homozygous recessive plant.

Fill in the Punnett square below and give the ratios for each question beneath the Punnett Square.

Key: G = green kernels, g = clear kernels

Genotype of parents: _GG_ x _gg_

Parent #1

Parent #2

What is the genotypic ratio of the offspring in Question 3?

What is the phenotypic ratio of the offspring in Question 3?

4. Yellow seeds are dominant over green seeds in pea plants. Cross a heterozygous (yellow seeded) plant with a green seeded plant.

Key: __________

Genotype of parents: __________ x __________

Parent #1

Parent #2

What is the genotypic ratio of the offspring in Question 4?

What is the phenotypic ratio of the offspring in Question 4?

5. Now cross two of the heterozygous F1 offspring from question #2.

Parent #1

Parent #2

What is the genotypic ratio of the offspring in Question 5?

What is the phenotypic ratio of the offspring in Question 5

Answer 1

​​​​​​In all the problems, the percentage of dominant character will be more than recessive character.