Lect. 10 - Dev. Genetics II Flashcards Preview

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Flashcards in Lect. 10 - Dev. Genetics II Deck (21):
1

Hierarchy order of genes in drosophila development

Egg polarity genes (maternal effect genes), segmentation genes, homeotic genes

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maternal effect genes aka egg polarity genes

important in the establishment of the dorsal-ventral and anterior posterior axes in the fruit fly

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egg polarity genes that establish the ventral-dorsal axis include:

dorsal, cactus, toll

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egg polarity genes that establish the anterior-posterior axis include:

bicoid, nanos, hunchback

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why are egg polarity genes also called maternal effect genes?

even though their mRNAs migrate to the eggs and are translated after fertilization, they are transcribed into mRNAs in the ovary BEFORE fertilization

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how do egg polarity genes work?

by setting up protein concentration gradients

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morphogen

a protein that varies in concentration and causes different developmental responses as a result of the concentration differences

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Where are dorsal, cactus, and toll genes expressed?

in the ovary

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cactus protein

binds dorsal protein and traps it in the cytoplasm

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toll protein

leads to the degradation of the cactus protein, allowing dorsal protein to move into the nuclei of the ventral cells

11

Nanos Protein

expressed in the ovary; regulates expression of genes responsible for posterior structures; inhibits translation of hunchback mRNA

12

Bicoid Protein

express in ovary; regulates expression of genes responsible for anterior structures and stimulates hunchback

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segmentation genes

transcribed after fertilization; Gap genes, pair-rule genes, segment-polarity genes

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what regulates the segmentation genes?

bicoid and nanos protein gradients

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gap genes

delete adjacent segments

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pair-rule genes

delete sam part of patter in every other segment

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segment-polarity gene

afftect polarity of segment

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homeotic genes

determines the identity of individual segments; expressed after fertilzation; contain homeobox; antennapedia and bithorax complex

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what activates the homeotic genes?

concentration of products of gap, pair-rule, and semgnet-polarity genes

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antennapedia complex

affects development of head and thorax

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bithorax complex

affects development of posterior thorax and abdominal segments