Chapter 12, Problem 9STP

Summary Introduction

To determine:

The dihybrid cross of heterozygous yellow round seeds using law of independent assortment.

Introduction:

The law of independent assortment was first observed by Gregor Johann Mendel in 1865 during his studies of genetics. This law describes how different factors called genes independently separate from one another when reproductive or germ cells develop. This law states that different genes and their alleles are inherited independently within sexually reproducing organisms. The Chromosomes are separated into multiple gametes during meiosis. The factor or genes linked on a chromosome can rearrange themselves through the process of crossing-over.

Explanation of Solution

A dihybrid cross refers to a cross between two organisms that are identically hybrid for two characters. A hybrid organism is one that is heterozygous, which means that is carries two different alleles at a particular locus.

In the given case, Heterozygous yellow, round (YyRr) seed pea plants are crossed. The gametes produced are YR, Yr, yR and yr.

The cross will be as shown in Punnett square:

Gametes	YR	Yr	yR	yr
YR	YYRR	YYRr	YyRR	YyRr
Yr	YYRr	YYrr	YyRr	Yyrr
yR	YyRR	YyRr	yyRR	yyRr
yr	YyRr	Yyrr	yyRr	yyrr

The phenotypic ratio of yellow round: yellow wrinkled: green round: green wrinkled will be 9:3:3:1