Late Nite Labs

Genetics of Corn
SHORT ANSWER
Experiment 1: A Monohybrid Cross
Directions: Use complete sentences and bold the answers and have them in a different color. Failure
to do so will result in points being deducted.
Lab Results
1. What proportion of purple kernels is expected in the progeny of the monohybrid cross in Experiment 1?

2. Fill in the table below with the data you collected during Experiment 1

Purple Kernels

Yellow Kernels

Row 1

Row 2

Row 3

Row 4

Row 5

Total

Data Analysis

3. Use the data you collected in Experiment 1 to calculate the percentage of each phenotype.

4. Suppose you observed 240 progeny that resulted from a monohybrid cross and involved genes that obeyed Mendelian
inheritance, how many heterozygous progeny would you expect to observe?

Experiment 2: A Dihybrid Cross
Lab Results
1. Fill in the table below with the data you collected during Experiment 2.

Purple, Smooth Kernels

Purple, Wrinkled Kernels

Yellow, Smooth Kernels

Yellow, Wrinkled Kernels

Row 1

Row 2

Row 3

Row 4

Row 5

Total

Data Analysis
2. Fill in the following table with the percentage of each type of kernel.
Phenotype
Purple, Smooth
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Proportion of Progeny

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Purple, Wrinkled

Yellow, Smooth

Yellow, Wrinkled

3. According to your results in Experiment 2, what would be the correct hypothesis to test to see if the traits were inherited
through Mendelian genetics? Record this answer for use in a later question.

4. For the cross in Experiment 2, how many degrees of freedom are there? Record this answer for use in a later question.

5. Determine the ?2 value for Experiment 2 using the following equation. Record your answer for use in a later question.
Phenotype

Observed

Expected

(O­E) 2

(O­E)

(O­E) 2/E

Purple, smooth

Purple, winkled

Yellow, smooth

Yellow, wrinkled

Sum

6. Use the degrees of freedom and ?2 value from earlier questions to determine the p value for Experiment 2 using the table
of critical values for ?2 . Record your answer for use in a later question.

Conclusions
1. Use the hypothesis, degrees of freedom, ?2 , and p value determined in earlier questions to conclude whether corn #2 is
following Mendelian genetics. Explain your reasoning.

2. If you crossed Cat #1 and Cat #2 and observed two unlinked traits that follow Mendelian genetics, what must the genotype
and phenotype of Cat #2 be?
Hair length:
Dominant = long hair (L)
Recessive = short hair (l)
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Coat color:
Dominant = white (W)
Recessive = some color (w)

3. In a test population of 1000 people, 200 display albinism. You hypothesize that this trait follows Mendelian genetics with a
3:1 ratio of non­albinism to albinism. Use the ?2 test to determine whether the data support the hypothesis or not. Show
your steps and explain your reasoning.
?2 = ? [(O – E)2 /E
where O is the observed number of individuals in a defined class, and E is the expected number of individuals in a defined
class based on the hypothesis. The ? symbol indicates that you should sum the results for each defined class.

Sources
Pierce et al., Genetics 2nd Edition.
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Late Nite Labs

4/4 BIO 111 – Genetics of Corn Experiment 1 A Monohybrid Cross

 

MORE INFO 

A Monohybrid Cross

Introduction

A monohybrid cross is a cross between two plants that are the same species. This can be useful for breeding certain traits in plants. In this article, we’ll go over all of the steps involved with making a monohybrid cross and what you will need to do so that you can use it later on!

Purpose

The purpose of a monohybrid cross is to determine the genotypic ratio of a plant. In other words, it’s used to determine how many homozygous dominant or recessive genes are present in one allele (either from each parent).

The phenotypic ratio can be used to predict whether your seedling will exhibit any traits that you’re interested in seeing in your final plant population.

Materials

Materials

• A plant (hopefully a monohybrid) and its paired seeds.

• A container to hold the plants while they grow, such as a plastic box with lid or an old shoebox with holes poked in it.

• A piece of paper for recording observations (and a pencil).

Procedure

You can cross two pure-bred strains to produce a hybrid. To do this, you will have to observe the phenotypes of the offspring and record them.

Afterwards, compare these data with their genotypes (the information stored in each parent’s DNA).

Analysis

You should now have a good understanding of the results of your crosses, and be able to make some predictions about what will happen.

You’ll find that your crosses are producing mostly true-breeding progeny, but not quite exactly as you expected. This is because there’s an element of randomness involved in any cross between two different species. For example, if you were breeding dogs with cats and expecting 75% of the puppies to be purebreds (like Labrador retrievers), then instead you would get 100% purebreds! That’s because one dog gene doesn’t tend to match very well with another dog gene—in fact, it might not even occur at all! So while this particular cross might produce 100% purebred dogs over time—maybe even within just a few generations after breeding stops—it doesn’t mean we can say anything meaningful about how each individual puppy was created or what its phenotype looked like when it was born (that is where epistasis comes into play).

Extensions

You can also make an additional test cross by crossing a backcross plant with another plant. This is called backcrossing, and it’s an effective way to maintain traits that aren’t readily available from other sources (such as wild varieties).

You may want to backcross your seeds if you want only one trait from one parent, or if you want two distinct traits from two parents. Once again, there are many different ways that you could do this—for example:

• A single-trait backcross (also known as single-parent) involves getting all the male gametes from one parent and injecting them into anther female gamete of another plant so that their offspring inherit half their genes from each parent. This results in 100% genetic material being shared between parents instead of 50%, which makes it easier for researchers who are trying out new techniques when working with plants!

• Multiple-trait backcrosses involve getting multiple genomes from different organisms together into one organism; this means having more specific information about how plants work than just looking at individual genes alone would provide.”

Takeaway:

Now that you know how to work with monohybrid crosses, it’s time for the big question: how do you use them?

You might be surprised at how simple this process is. The only real decision you need to make is which parent to breed with and when. Here are some tips on doing so!

Conclusion

I hope this article has been helpful to you in understanding how a monohybrid cross works and why it is so important. There are many different ways that these crosses can be done and each one has its own advantages, but I think this one has some great benefits because it gives you more flexibility when selecting your parents’ genotypes. If you want to learn more about breeding different plants together, head over to our other articles at www.plantedscience.com/articles!