Regulation of Gene Expression

Page
11

mRNA

mRNA

mRNA

Myosin, other

muscle proteins,

and cell cycle–

blocking proteins

Part of a muscle fiber

(fully differentiated cell)

MyoD

Another

transcription

factor

Slide 76

Pattern Formation: Setting Up the Body Plan

Pattern formation is the development of a spatial organization of tissues and organs

In animals, pattern formation begins with the establishment of the major axes

Positional information, the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells

Slide 77

Pattern formation has been extensively studied in the fruit fly Drosophila melanogaster

Combining anatomical, genetic, and biochemical approaches, researchers have discovered developmental principles common to many other species, including humans

Slide 78

The Life Cycle of Drosophila

In Drosophila, cytoplasmic determinants in the unfertilized egg determine the axes before fertilization

After fertilization, the embryo develops into a segmented larva with three larval stages

Slide 79

Fig. 18-17

Thorax

Head

Abdomen

0.5 mm

Dorsal

Ventral

Right

Posterior

Left

Anterior

BODY

AXES

Follicle cell

(a) Adult

Nucleus

Egg

cell

Nurse cell

Egg cell

developing within

ovarian follicle

Unfertilized egg

Fertilized egg

Depleted

nurse cells

Egg

shell

Fertilization

Laying of egg

Body

segments

Embryonic

development

Hatching

0.1 mm

Segmented

embryo

Larval stage

(b) Development from egg to larva

1

2

3

4

5

Slide 80

Fig. 18-17a

Thorax

Head

Abdomen

0.5 mm

Dorsal

Ventral

Right

Posterior

Left

Anterior

BODY

AXES

(a) Adult

Slide 81

Fig. 18-17b

Follicle cell

Nucleus

Egg

cell

Nurse cell

Egg cell

developing within

ovarian follicle

Unfertilized egg

Fertilized egg

Depleted

nurse cells

Egg

shell

Fertilization

Laying of egg

Body

segments

Embryonic

development

Hatching

0.1 mm

Segmented

embryo

Larval stage

(b) Development from egg to larva

1

2

3

4

5

Slide 82

Genetic Analysis of Early Development: Scientific Inquiry