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BIO 448 MOLECULAR BIOLOGY OF DIFFERENTIATION

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(1)

BIO 448

MOLECULAR BIOLOGY OF

DIFFERENTIATION

(2)

Role of Differential Gene Expression in Establishing Body Segmentation

fruit fly; Drosophila

(3)

Maternal Effect Genes

• Determine Polarity

• Polarity depends on the distribution of the morphogen.

(4)

Maternal Effect Genes

• Morphogens are products of the specific

“maternal effect genes” in the mother and are often distributed unevenly to the eggs.

• determines the dorsoventral (back-abdomen) and anteroposterior (head-tail) axes.

(5)

• bicoid

• nanos

Segmentarion genes and Homeotic Genes

(6)

Segmentarion genes

• show their effects after maternal effect genes

• the number, limits, and polarity of the larval segments are determined by the proteins encoded by the segmentation genes.

• maternal effect genes activate the segmentation genes.

(7)

• Three classes of segmentation genes

• gap genes

• double rule genes

• segment polarity genes

(8)

• gap genes: organize large areas

along the anteroposterior axis.

(9)

• double rule genes: divide the

embryo into two segmented units

each.

(10)

• segment polarity genes: determine

the boundaries of the segments and

the anteroposterior organization.

(11)

• provides differences between segments

• Exp. Drosophila

Homeotic Genes

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