Regulation of Gene Expression

Page
12

Edward B. Lewis, Christiane Nüsslein-Volhard, and Eric Wieschaus won a Nobel 1995 Prize for decoding pattern formation in Drosophila

Lewis demonstrated that genes direct the developmental process

Slide 83

Fig. 18-18

Antenna

Mutant

Wild type

Eye

Leg

Slide 84

Fig. 18-18a

Antenna

Wild type

Eye

Slide 85

Fig. 18-18b

Mutant

Leg

Slide 86

Nüsslein-Volhard and Wieschaus studied segment formation

They created mutants, conducted breeding experiments, and looked for corresponding genes

Breeding experiments were complicated by embryonic lethals, embryos with lethal mutations

They found 120 genes essential for normal segmentation

Slide 87

Axis Establishment

Maternal effect genes encode for cytoplasmic determinants that initially establish the axes of the body of Drosophila

These maternal effect genes are also called egg-polarity genes because they control orientation of the egg and consequently the fly

Animation: Development of Head-Tail Axis in Fruit Flies

Slide 88

One maternal effect gene, the bicoid gene, affects the front half of the body

An embryo whose mother has a mutant bicoid gene lacks the front half of its body and has duplicate posterior structures at both ends

Bicoid: A Morphogen Determining Head

Structures

Slide 89

Fig. 18-19

Tail

Tail

Tail

Head

Wild-type larva

T1

T2

T3

A1

A2

A3

A4

A5

A6

A7

A8

A8

A7

A6

A7

A8

Mutant larva (bicoid)

EXPERIMENT

RESULTS

CONCLUSION

Fertilization,

translation

of bicoid

mRNA

Bicoid protein in early

embryo

Anterior end

Bicoid mRNA in mature

unfertilized egg

100 µm

bicoid mRNA

Nurse cells

Egg

Developing egg

Bicoid mRNA in mature unfertilized egg

Bicoid protein in early embryo

Slide 90

Fig. 18-19a

T1

T2

T3

A1

A2

A3

A4

A5

A6

A7

A8

A8

A7

A6

A7

Tail

Tail

Tail

Head

Wild-type larva

Mutant larva (bicoid)

EXPERIMENT

A8

Slide 91