Week 3 Objective 1 Genetic hierarchy control of development in drosophilia

Question 1

Gene hierarchy (3)

Answer 1

maternal-effect genes

segmentation genes

a. pair-rule genes
b. segment-polarity genes
c. Gap genes

homeotic genes

a. antennapedia complex (Hox)
b. Bithorax complex (Hox)

Question 2

Maternal-effect genes function

Answer 2

establishes gradients from anterior and posterior poles of the egg

Question 3

Segmentation genes function

Answer 3

defines broad regions in the egg

Question 4

Pair rule genes function

Answer 4

regional sections of embryo defined, in drosophila they define 7 segments

Question 5

segment polarity genes function

Answer 5

polarity of individual segments (in drosophila, defines 14 segments)

Question 6

homeotic genes function

Answer 6

determines regional characteristics

Question 7

Drosophilia development (overview)

Answer 7

hollow cylinder —> segmented embryo at 5-10 hours —> larvae that passes through 3 stages —> metamorphosis —> pupa (5 days) —-> adult (9 days, roughly)

Question 8

Drosophila zygote

Answer 8

single celled fusion of egg+ sperm, 2n

Question 9

Drosophila multinucleate syncytium

Answer 9

single cell under goes multiple rounds of mitotic division without cytokinesis, producing a syncytium

Question 10

Drosophila syncytial blastoderm

Answer 10

nuclei migrate to peripheries of embryo, divind several more times, creating a syncytial blastoderm with pole nuclei

Question 11

Drosophila blastoderm

Answer 11

membrane grows around each cell, producing a defined layer of cells surrounding embryo. structure is called blastoderm

Question 12

Drosophila Pole cells

Answer 12

nuclei at end of blastoderm develop into a pole cells, which become primordial germ cells

Question 13

Drosophila axis and segmentation 2 hrs –> 10 hrs —> adult

Answer 13

2 hrs = anterior/posterior, dorsal/ventral axes of embryo established

10 hrs = all segments are established (head, thoracic, abdominal segments)

8 days, segments fully developed into adult

Question 14

Drosophila: Dorsal protein

Answer 14

AFTER nuclei migrate to periphery of embryo

dorsal protein becomes concentrated in nuclei of ventral surface

Question 15

Drosophila: bicoid protein

Answer 15

bicoid mRNA is localized at anterior end of the egg

bicoid protein forms a gradient with high concentration at the anterior end which induces development of anterior structures of a fruit fly

Question 16

Drosophila: Nanos protein

Answer 16

Nanos protein located at posterior end of the egg

after fertilization, nanos mRNA is translated in nanos proteins, which becomes concentrated at the posterior end of the egg and inhibits formation of anterior structures

Question 17

Drosophila: Segmentation

Answer 17

segmentation occurs

Question 18

Sequential gene expression

Answer 18

the arrangement of genes on the chromosome corresponds to the sequence in which the genes are expressed along anterior-posterior axis

Question 19

Sequence of Development flow chart

Answer 19

single celled egg—> Egg Polarity Genes —> Determination of major body axes —> Gap genes —> Regional sections of embryo defined —> Paired rule genes —> individual segments defined —> Homeotic genes —> identity of individual segments defined