Slide 1

Chapter 15:The Chromosomal

Basis of Inheritance

Figure 15.1

Figure 15.2P Generation

F1 Generation

Yellow-roundseeds (YYRR)

Green-wrinkledseeds (yyrr)

Meiosis

Fertilization

Gametes

Y

Y R R

YR

y

y r

y r

All F1 plants produceyellow-round seeds (YyRr).

Meiosis

Metaphase I

Anaphase I

Metaphase II

R R

R R

R R

R R

R R R R

r r

r r

r r

r r

r r r r

Y Y

Y Y

Y Y

Y Y

Y Y Y Y

y y

y y

y y

y y

yy y y

Gametes

LAW OF SEGREGATIONThe two alleles for each

gene separate duringgamete formation.

LAW OF INDEPENDENTASSORTMENT Alleles of genes

on nonhomologous chromosomesassort independently during

gamete formation.

1

2 2

1

1/41/4

1/41/4YR yr Yr yR

F2 Generation3 3Fertilization recombines

the R and r alleles at random.

Fertilization results in the 9:3:3:1 phenotypic ratio

in the F2 generation.

An F1 F1 cross-fertilization

9 : 3 : 3 : 1

r

Figure 15.3

Thomas Hunt Morgan and his Fruit Flies

Figure 15.4

All offspringhad red eyes.

PGeneration

F1Generation

F2Generation

F2Generation

F1Generation

PGeneration

Eggs

Eggs

Sperm

Sperm

XX

XY

w

w

ww w

w

ww w

w

w

w

w

w

ww w

RESULTS

EXPERIMENT

CONCLUSIONMorgan’s Experiment

Figure 15.6

Parents

orSperm

or

Egg

Zygotes (offspring)

44 XY

44 XX

22 X

22 Y

22 X

44 XX

44 XY

22 XX

22 X

76 ZW

76 ZZ

32 (Diploid)

16 (Haploid)

(a) The X-Y system

(b) The X-0 system

(c) The Z-W system

(d) The haplo-diploid system

Sex Determination

Figure 15.5

X

Y

Human Sex Chromosomes

Figure 15.7

Eggs Eggs Eggs

Sperm Sperm Sperm

(a) (b) (c)

XNXN XnY XNXn XNY XNXn XnY

Xn Y XN Y YXn

Xn Xn

XN

XN

XN XNXNXn XNY

XNY

XNY XNY

XnY XnYXNXn XNXn

XNXnXNXN

XnXn

Sex Linked Genes

Figure 15.8

Early embryo:

X chromosomesAllele for

orange fur

Allele forblack fur

Two cellpopulationsin adult cat:

Cell division andX chromosome

inactivation

Active X Inactive X Active X

Black fur Orange fur

X Inactivati

on

Figure 15.9-1P Generation (homozygous)

Wild type(gray body, normal wings)

b b vg vg b b vg vg

Double mutant(black body,

vestigial wings)

EXPERIMENT

Figure 15.9-2P Generation (homozygous)

Wild type(gray body, normal wings)

F1 dihybrid(wild type) TESTCROSS

b b vg vg

b b vg vg

b b vg vg

b b vg vg

Double mutant(black body,

vestigial wings)

Double mutant

EXPERIMENT

Figure 15.9-3P Generation (homozygous)

Wild type(gray body, normal wings)

F1 dihybrid(wild type)

Testcrossoffspring

TESTCROSS

b b vg vg

b b vg vg

b b vg vg

b b vg vg

Double mutant(black body,

vestigial wings)

Double mutant

Eggs

Sperm

EXPERIMENT

Wild type(gray-normal)

Black-vestigial

Gray-vestigial

Black-normal

b vg b vg b vg b vg

b b vg vg b b vg vg b b vg vg b b vg vg

b vg

Figure 15.9-4P Generation (homozygous)

Wild type(gray body, normal wings)

F1 dihybrid(wild type)

Testcrossoffspring

TESTCROSS

b b vg vg

b b vg vg

b b vg vg

b b vg vg

Double mutant(black body,

vestigial wings)

Double mutant

Eggs

Sperm

EXPERIMENT

RESULTS

PREDICTED RATIOS

Wild type(gray-normal)

Black-vestigial

Gray-vestigial

Black-normal

b vg b vg b vg b vg

b b vg vg b b vg vg b b vg vg b b vg vg

965 944 206 185

1

1

1

1

1

0

1

0

If genes are located on different chromosomes:

If genes are located on the same chromosome andparental alleles are always inherited together:

:

:

:

:

:

:

:

:

:

b vg

Figure 15.UN01

Most offspring

F1 dihybrid femaleand homozygous

recessive malein testcross

or

b+ vg+

b vg

b+ vg+

b vg

b vg

b vg

b vg

b vg

Figure 15.UN02

Gametes from green-wrinkled homozygousrecessive parent (yyrr)

Gametes from yellow-rounddihybrid parent (YyRr)

Recombinant offspring

Parental-type

offspring

YR yr Yr yR

yr

YyRr yyrr Yyrr yyRr

Figure 15.10Testcross

parents

Replicationof chromosomes

Gray body, normal wings(F1 dihybrid)

Black body, vestigial wings(double mutant)

Replicationof chromosomes

Meiosis I

Meiosis II

Meiosis I and II

Recombinantchromosomes

Eggs

b vg

b vg

b vg

b vg

b vg

b vgb vg

b vg

b vg

b vg

b vg

b vg

b vg

b vgb vg

b vg

bvg b vgb vg b vg

Testcrossoffspring

965Wild type

(gray-normal)

944Black-

vestigial

206Gray-

vestigial

185Black-normal

Sperm

Parental-type offspring Recombinant offspring

Recombinationfrequency

391 recombinants2,300 total offspring 100 17%

b vg b vgb vgb vg

b vg b vg b vg b vg

b vg

Figure 15.10a

Testcrossparents

Replicationof chromosomes

Gray body, normal wings(F1 dihybrid)

Black body, vestigial wings(double mutant)

Replicationof chromosomes

Meiosis I

Meiosis II

Meiosis I and II

Recombinantchromosomes

Eggs

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vg

b vgb vg

b vg

bvg b vgb vg

b vg

Spermb vg

Figure 15.10b

Testcrossoffspring

965Wild type

(gray-normal)

944Black-

vestigial

206Gray-

vestigial

185Black-normal

Sperm

Parental-type offspring Recombinant offspring

Recombinationfrequency

391 recombinants2,300 total offspring

100 17%

b vg b vgb vgb vg

b vg b vg b vg b vg

b vg

Eggs

Recombinantchromosomes

bvg b vg b vg b vg

Figure 15.11

Chromosome

Recombinationfrequencies

9% 9.5%

17%

b cn vg

RESULTS

Figure 15.12

Mutant phenotypesShort

aristaeBlackbody

Cinnabareyes

Vestigialwings

Browneyes

Long aristae(appendages

on head)

Gray body

Red eyes

Normalwings

Redeyes

Wild-type phenotypes

104.567.057.548.50

Slide 21

Chromosomal Mutations

• Alteration of chromosome Alteration of chromosome numbernumber

• AneuploidyAneuploidy• Monosomic (2n – 1)Monosomic (2n – 1)• Trisomic (2n + 1)Trisomic (2n + 1)

• PolyploidyPolyploidy• Alteration in chromosome Alteration in chromosome

structurestructure

Slide 22

Chromosomal Mutations

• Alteration of chromosome Alteration of chromosome numbernumber

• AneuploidyAneuploidy• Monosomic (2n – 1)Monosomic (2n – 1)• Trisomic (2n + 1)Trisomic (2n + 1)

• PolyploidyPolyploidy• Alteration in chromosome Alteration in chromosome

structurestructure

Figure 15.13-3 Meiosis I

Meiosis II

Nondisjunction

Non-disjunction

Gametes

Number of chromosomes

Nondisjunction of homo-logous chromosomes in

meiosis I

(a) Nondisjunction of sisterchromatids in meiosis II

(b)

n 1 n 1n 1 n 1 n 1n 1 n n

Figure 15.15

Slide 25

Aneuploidy in Sex Chromosomes

Slide 26

Chromosomal Mutations

• Alteration of chromosome Alteration of chromosome numbernumber

• AneuploidyAneuploidy• Monosomic (2n – 1)Monosomic (2n – 1)• Trisomic (2n + 1)Trisomic (2n + 1)

• PolyploidyPolyploidy• Alteration in chromosome Alteration in chromosome

structurestructure

Slide 27

Chromosomal Mutations

• Alteration of chromosome numberAlteration of chromosome number• AneuploidyAneuploidy

• Monosomic (2n – 1)Monosomic (2n – 1)• Trisomic (2n + 1)Trisomic (2n + 1)

• PolyploidyPolyploidy• Alteration in chromosome Alteration in chromosome

structurestructure

Figure 15.14(a) Deletion

(b) Duplication

(c) Inversion

(d) Translocation

A deletion removes a chromosomal segment.

A duplication repeats a segment.

An inversion reverses a segment within a chromosome.

A translocation moves a segment from onechromosome to a nonhomologous chromosome.

A B C D E F G H

A B C E F G H

A B C D E F G H

A B C D E F G H B C

A B C D E F G H

A D C B E F G H

A B C D E F G H M N O P Q R

GM N O C H FED A B P Q R

Figure 15.16

Normal chromosome 9

Normal chromosome 22

Reciprocal translocation

Translocated chromosome 9

Translocated chromosome 22(Philadelphia chromosome)

Slide 30

Exceptions to Chromosome Theory

• Genomic imprintingGenomic imprinting• Organelle genesOrganelle genes