Lab 2 - pattern formation in drosophila

Question 1

What is the egg type and cleavage type of drosophila?

Answer 1

egg type = centrolecithal
cleavage type = superficial meroblastic –> creates a syncytium

Question 2

Briefly describe drosophila’s life cycle

Answer 2

egg –> larva (3 stages) –> pupa –> adult

Question 3

Describe the segmentation pattern of drosophila

Answer 3

(A) - head - T1–>T3 - A1–>A8 - (P)

Question 4

What are maternal effect genes?

Answer 4

bicoid and nanos produce two gradients which activate or repress the gap genes

Question 5

What are gap genes?

Answer 5

• expressed in specific broad regions
• subdivide the embryo
• regulate the expression of pair rule genes

Question 6

What are pair rule genes?

Answer 6

• divides the embryo into periodic units
• expressed in alternative parasegments –> further subdividing the embryo
• activate the segment polarity genes

Question 7

What are segment polarity genes?

Answer 7

establish the final position and polarity of the 14 parasegments

Question 8

What are Hox genes?

Answer 8

• determine the developmental fate of each segment
• protein products of the gap, pair and segment genes interact to regulate the Hox genes

Question 9

Describe the maternal effect gene gradient

Answer 9

(A) - bicoid mRNA
- high [bicoid] no [nanos] –> head most region
(P) - nanos mRNA
- no [bicoid] high [nanos] –> tail forming region

Question 10

Name the four gap genes that are expressed A –> P

Answer 10

(A) - hunchback - kruppel - knirps - caudal - (P)

Question 11

What happens if the gene is non functional for each of the following types of genes: gap, pair-rule, segment polairty?

Answer 11

• gap = segments missing
• pair-rule = missing every second segment
• segment polarity = defects in every segment

Question 12

Describe the characterisitcs of the gap mutants knirps and kruppel

Answer 12

knirps:
- normal thorax
- only two abdominal bands - A1 + A8 (A1 is expanded)

kruppel:
- lack thorax and anteriorioir abdomen
- A6 is duplicated mirror image –> football shaped hole in A6 fusion
- normal A7 + A8

Question 13

Describe the characterisitcs of the pair rule mutants: even-skipped and odd-skipped

Answer 13

even-skipped
- missing T1, T3, A2, A4, A6, A8
- 5 denticle bands present

odd-skipped
- missing T2, A1, A3, A5, A7
- 6 denticle bands present

Question 14

Describe the characterisitcs of the segment polarity mutants wingless and engrailed

Answer 14

Wingless
- lack all segment boundaries
- entire ventral abdsomen covered with denticles
- missing head

Engrailed
- substantial deletion of the posterior region of even-numbered segments
- formation of doublets