Module 6 Lesson 3 - 6 (Lab)

Lab: Chicken Genetics (one trait)

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Introduction

Not all genes have one dominant and one recessive allele. Sometimes, the presence of any allele leads to some kind of change in phenotype. With flower phenotype, one of each allele produces a blend, and the resulting phenotype is pink.

In this simulation, you will explore chicken colours. You will conduct various breeding cycles until you determine the mode of inheritance and until you can answer the questions based on codominance.

Background

Different versions of the same gene are called alleles. Organisms inherit one copy of an allele from each parent. Thus, an organism has two alleles per gene. These two alleles make up the organism's genotype. The way the alleles interact with each other and the environment control how the gene is expressed. The physical expression of a gene is the organism’s phenotype.

Gregor Mendel studied traits in pea plants that were governed by a dominant-recessive inheritance pattern. In a dominant-recessive pattern, one version of a gene is dominant over another version. If the dominant allele is present, it always will be expressed. The recessive allele will be expressed only if the dominant allele is absent.

Many other patterns of inheritance occur in addition to the dominant-recessive pattern. The table below summarizes some of the other patterns of inheritance.

Inheritance Pattern	Description
Codominance	the phenotypes produced by both alleles are completely expressed
Incomplete dominance	one allele is not completely dominant over another allele
Multiple alleles	a gene that is governed by more than two alleles
Polygenic traits	a trait that is controlled by two or more genes

The pattern of inheritance modelled by the Chicken Genetics Gizmo is codominance. The Gizmo reflects a real-world example of codominance. In several chicken breeds, feather colour is determined by codominant alleles. For example, crossing a white-feathered chicken with a red-feathered chicken will produce the hybrid red-white chicken.

Problem

Breeding chickens has never been easier! You will complete a Gizmo on Chicken Genetics and all the activities indicated in the lab. Manipulate the P1 breeding pair and observe the resulting offspring to determine the mode of inheritance for colour in chickens.

Materials

For this simulation, you need access to the Internet and a word processing program to record your results.

Procedure

Open the Gizmo, Chicken Genetics 

In this investigation, you will follow the instructions listed in the Exploration Guide for the part titled "Activity A: Codominant Trait". The top two spots in the hen house are the P1, or parental generation. Whichever two chickens you place here will breed to produce the other five spots you see in the hen house.

As you read and follow the instructions, be sure you are able to answer the questions listed for yourself

Analysis

1. One red and one white chicken were bred in this lab. 
   
   
   1. What kind of offspring results?
      
   2. Does it matter how many times you click "breed"?
      


2. Two heterozygous birds were bred in this lab.
   
   
   1. What kind of offspring results after 25 crosses?
      
   2. What is the phenotypic ratio of the offspring?
      
   3. Which pattern of inheritance is this?
      

Assessment Questions

Complete the assessment questions in the simulation and check your answers.