Chapter 4.2, Problem 36AQP

a.

Summary Introduction

To determine:

The mode of inheritance of signed and purple.

Introduction:

Genotypic is the genetic constitution of an individual organism, “Drosophila melanogaster”. The drosophila is a genus of flies, belonging to the family of “drosophilidae”, and phylum “Arthropoda”. It is also known by the name of fruit fly.

Explanation of Solution

When homozygous flies singed and purple and homozygous flies for normal bristle and eye color are crossed ${\text{F}}_{\text{1}}$ progeny produced,

In cross I is $420$ female, normal bristles, red eyes and $426$ male, normal bristles, red eyes

${\text{F}}_{\text{2}}$ progeny produced:

“$337$ female, normal bristles, red eyes

$113$ female, normal bristles, purple eyes

$168$ male, normal bristles, red eyes

$170$ male, singed bristles, red eyes

$56$ male, normal bristles, purple eyes

$58$ male, singed bristles, purple eyes”

Cross II: When female, singed bristles, purple eyes crossed with male, normal bristles, red eyes then ${\text{F}}_{\text{1}}$ progeny produced is:

504 female, normal bristles, red eyes and 498 male, singed bristles, red eyes.

${\text{F}}_{\text{2}}$ Progeny produced:

“227 female, normal bristles, red eyes

223 female, singed bristles, red eyes

225 male, normal bristles, red eyes

225 male, singed bristles, red eyes

78 female, normal bristles, purple eyes

76 female, singed bristles, purple eyes

74 male, normal bristles, purple eyes

72 male, singed bristles, purple eyes”

In cross I, ${\text{F}}_{\text{1}}$ progeny has normal bristle it mean that allele for singed bristles s is recessive to normal bristles allele S. but in the cross II ${\text{F}}_{\text{1}}$ progeny female is having normal bristles and male is having singed bristles, it mean that it is an X-linked trait. So the mode of inheritance in signed is X-linked.

In cross I, ${\text{F}}_{\text{1}}$ progeny has all red eyes that mean allele for purple eyes p is recessive to the allele for red color of eye P. in both the cross I and II, color of the eye is red. Hence it is an autosomal trait, so the mode of inheritance is autosomal.

b.

Summary Introduction

To determine:

The genotype of parent and offspring in the P, ${\text{F}}_{\text{1}}$ and ${\text{F}}_2$ generation of cross I and II.

Introduction:

Genotypic is the genetic constitution of an individual organism, “Drosophila melanogaster”. The drosophila is a genus of flies, belonging to the family of “drosophilidae”, and phylum “Arthropoda”. It also known by the name of fruit fly.

Explanation of Solution

Pictorial representation:

Fig 1. Showing cross I, ${\text{F}}_{\text{1}}$ and ${\text{F}}_{\text{2}}$ between males with homozygous allele for singed bristles (${\text{X}}^{\text{s}}\text{Y}$) and purple eyes ($\text{pp}$) and female with homozygous allele for normal bristles (${\text{X}}^{\text{+}}{\text{X}}^{\text{+}}$ ) and red eyes ($\text{PP}$)

Fig 1: genotype of ${\text{F}}_{\text{1}}$ and ${\text{F}}_{\text{2}}$

Fig 2: Showing cross II, ${\text{F}}_{\text{1}}$ and ${\text{F}}_{\text{2}}$ between males with homozygous allele for normal bristles (${\text{X}}^{\text{s}}\text{Y}$) and red eyes ($\text{PP}$) and female with homozygous allele for singed bristles (${\text{X}}^{\text{s}}{\text{X}}^{\text{s}}$ ) and purple eyes ($\text{pp}$)

Fig 2:  genotype of ${\text{F}}_{\text{1}}$ and ${\text{F}}_{\text{2}}$

To determine the genotype of cross I and II, first assume the symbol for the genes.

For bristles: this X-linked trait so dominant allele will be ${\text{X}}^{\text{+}}$ for normal bristles and for recessive allele will be ${\text{X}}^{\text{s}}$ for singed bristle.

For color of eyes: this is autosomal mode of inheritance, so its dominant allele p, will be normal red eye color a recessive allele p will be purple eye color.

In cross I, P generation of males with homozygous allele for singed bristles (${\text{X}}^{\text{s}}\text{Y}$) and purple eyes ($\text{pp}$) and female with homozygous allele for normal bristles (${\text{X}}^{\text{+}}{\text{X}}^{\text{+}}$ ) and red eyes ($\text{PP}$) are crossed as shown in fig 1.

${\text{F}}_{\text{1}}$ Generation of cross I genotype:

337 female, normal bristles, red eyes: ${\text{X}}^{\text{s}}{\text{X}}^{\text{+}}\text{PP,}{\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{PP,}{\text{X}}^{\text{+}}{\text{X}}^{\text{+}}\text{Pp}\text{and}{\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{Pp}$

113 female, normal bristles, purple eyes: ${\text{X}}^{\text{+}}{\text{X}}^{\text{+}}\text{pp}\text{and}{\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{pp}$

168 male, normal bristles, red eyes: ${\text{X}}^{\text{+}}\text{Y}\text{PP}\text{and}{\text{X}}^{\text{+}}\text{Y}\text{Pp}$

170 male, singed bristles, red eyes: ${\text{X}}^{\text{s}}\text{Y}\text{PP}\text{and}{\text{X}}^{\text{s}}\text{Y}\text{Pp}$

56 male, normal bristles, purple eyes: ${\text{X}}^{\text{+}}\text{Y}\text{pp}$

58 male, singed bristles, purple eyes:${\text{X}}^{\text{s}}\text{Y}\text{pp}$.

In cross II, P generation of males with homozygous allele for normal bristles (${\text{X}}^{\text{s}}\text{Y}$) and red eyes ($\text{PP}$) and female with homozygous allele for singed bristles (${\text{X}}^{\text{s}}{\text{X}}^{\text{s}}$ ) and purple eyes ($\text{pp}$) are crossed as shown in fig 2.

$F_2$ Generation of cross II genotype:

227 female, normal bristles, red eyes: ${\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{PP}\text{and}{\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{Pp}$

223 female singed bristles, red eyes: ${\text{X}}^{\text{s}}{\text{X}}^{\text{s}}\text{PP}\text{and}{\text{X}}^{\text{s}}{\text{X}}^{\text{s}}\text{Pp}$

225 male, normal bristles, red eyes: ${\text{X}}^{\text{+}}\text{YPP}\text{and}{\text{X}}^{\text{+}}\text{Y}\text{Pp}$

225 male, singed bristles, red eyes: ${\text{X}}^{\text{s}}\text{YPP}\text{and}{\text{X}}^{\text{s}}\text{Y}\text{Pp}$

78 female, normal bristles, purple eyes: ${\text{X}}^{\text{+}}{\text{X}}^{\text{s}}\text{pp}$

76 female singed bristles, purple eyes: ${\text{X}}^{\text{s}}{\text{X}}^{\text{s}}\text{pp}$

74 male, normal bristles, purple eyes:${\text{X}}^{\text{+}}\text{Y}\text{pp}$

72 male, singed bristles, purple eyes: ${\text{X}}^{\text{s}}\text{Y}\text{pp}$