Ch 15 pictures

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Historical PerspectiveHistorical Perspective

1860’s Mendel proposed1860’s Mendel proposedthat discrete factors that discrete factors segregated and independentlysegregated and independentlyassorted during gameteassorted during gameteformation.formation.

GeneticsGenetics CytologyCytology

1875: Cytologists worked out1875: Cytologists worked outthe process of mitosis.the process of mitosis.

1890: Cytologists worked out1890: Cytologists worked outthe process of meiosis.the process of meiosis.

1900: Three botonists1900: Three botonists(Correns, deVries and (Correns, deVries and von Seysenegg) independently von Seysenegg) independently rediscovered Mendel’s Principlesrediscovered Mendel’s Principles20 years after his death.20 years after his death.

Early 1902: Walter Sutton, Theodor Boveri and others hypothesized that genes are on chromosomes.

Thomas Hunt Morgan

Drosophila melanogaster

Morgan’s SymbolsMorgan’s SymbolsWild TypeWild Type MutantMutant

Morgan’s SymbolsMorgan’s Symbols

(homozygote recessive)(homozygote recessive)(heterozygote)(heterozygote)

White Eyes = wWhite Eyes = wRed Eyes = w+ Red Eyes = w+ w+w ww

Morgan’s SymbolsMorgan’s Symbols

Curly Wings

Question 15.1

Sex-linkage in DrosophilaSex-linkage in Drosophila

First Filial Generation of Fruit Flies

Male

Female

w+(X chromosome)

w+ w

w (X chromosome) Y chromosome

w+(X chromosome)

w+ w w+ y

w+ y

F1 PhenotypeAll redEyes

GenotypeFemales= w+w

Males=w+y

Parentals

Second Filial Generation of Fruit Flies

Male

Female

w+(X chromosome)

w+ w

w+ (X chromosome) Y chromosome

w(X chromosome)

w+ w+ w+ y

w y

F23/4 redeyes

1/4 whiteeyes

Only males had

white eyes

F1 generation

Y Chromosome in Humans

Recessive Disorders

Red-green colorblindness

Duchenne muscular Dystrophy (muscles break down and are eventually lost)

Hemophilia (missing Blood clotting factor)

Question 15.2

Colorblind Inheritance Colorblind Inheritance in Femalesin Females

XcbXcb

Mother

Father

Xcb

XcbY

Alterations in ChromosomesAlterations in Chromosomes

Fig 15.12 Meiotic NondisjunctionFig 15.12 Meiotic Nondisjunction

One copy of Chromosome #1

No chromosome#1

Fertilization

One Chromosome #1X Embryonic

LethalAll otherspaired

Monosomy XOMonosomy XO

Trisomy XXY

Trisomy Chromosome 21Trisomy Chromosome 21(not in a sex chromosome)(not in a sex chromosome)

Fig 15.14: Alterations in Chromosome Structure

Chromosome 5 deletion

Question 15.3

X inactivation and the tortoiseshell cat

Figure 15.9 Some chromosomal systems of sex determination

Question 15.4