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Chapter 18 INVESTIGATIONS

How Do Environmental Factors

Affect Gene Expression?

Many environmental factors can affect the phenotype of a

plant. Traits such as growth rate, colour, leaf size, and leaf

shape can be affected by environmental factors such as light

intensity, hours of darkness, wavelength of radiation, and air

temperature. In this investigation, you will design an exper-

iment to explore how one environmental factor of your choice

affects the phenotype of a plant.

You can find more information about designing an exper-

iment in Appendix A1. Have your teacher check the procedure

before beginning the experiment. Then, write a lab report,

following the guidelines in Appendix A3.

Purpose Design Analysis

Problem Materials Evaluation

Hypothesis Procedure Synthesis

Prediction Evidence

INVESTIGATION 18.1 Report Checklist

Genetics of Corn

Corn is one of the world’s most important food crops. It has been

subject to selective breeding techniques and hybridization

for many years, which have resulted in vigorous, high-yielding

varieties. Nearly all corn grown today is hybrid corn. Some

varieties of corn are chosen for their sweet flavour while the

mixed coloration of other, inedible varieties makes them pop-

ular decorations during the autumn months.

Purpose

To determine the genotypes of parents by examining pheno-

types of corn for two different and independent traits.

Problem

To determine the probable genotypes of the parents of the

sample corn ears.

Materials

dihybrid corn ears (sample A, sample B)

Procedure

1. Obtain a sample A corn ear from your instructor
   (Figure 1). The kernels display two different traits
   that are located on different chromosomes.

Purpose Design Analysis

Problem Materials Evaluation

Hypothesis Procedure Synthesis

Prediction Evidence

Report Checklist

620 Chapter 18 NEL

INVESTIGATION 18.2

Figure 1

(a) Indicate the two different traits.

(b) Predict the dominant phenotypes.

(c) Predict the recessive phenotypes.