Lecture 3

Question 1

Name 4 measurable courtship parameters

Answer 1

• Total time courting during observation period
• Latency to initiate courtship
• Latency to copulation
• Courtships steps performed (order, latency and total duration)

Question 2

Name the 4 courtship signals and how they were discovered

Answer 2

Visual - Measured under red light to remove visual stimuli

Olfactory - Measure using mutant flies lacking olfaction (Or83b gene knocked out loses sense of smell)

Auditory - Measure using mutant flies lacking audition

Gustatory - Measure using mutant flies lacking gustation - Don’t progress courtship as well

Question 3

How do male and female flies communicate

Answer 3

Orientation - males sees and smells female

Tapping - Male tastes pheromones on female

Wing extension - Male extends wing closest to females head to play ‘love song’

Wing vibration - Involves olfaction and audition

Licking - Involves gustation and audition

(Attempted) copulation - Male passes on sperm and proteins (sex peptide) to female reproductive system

Question 4

Explain what pheromones female fruit flies have

Answer 4

Mixture of 7, 11-heptacosadiene (7, 11-HD) and 7, 11-nonacosadiene (7, 11-ND) on surface of cuticle

Attractive to males, and allows males to identify same species

Question 5

Explain what pheromones female fruit flies have

Answer 5

Mixture of 11-cis vaccenyl acetate (cVA), 7-tricosene (7-T), and 7-pentacosene (7-P) on surface of cuticle

Attracts females
Inhibit or elicit aggression in other males

Question 6

Explain visual signals in flies

Answer 6

• LC10 visual neurons required for tracking fly-sized object
• LC10 neurons sense moving visual objects
• Activation of LC10 neurons elicits courtship

Object motion -> Unilateral LC10 activation -> Ipsilateral turn and wing extension

Question 7

How do female flies recognise males

Answer 7

• Species-specific ‘love song’
• Song stimulates females to become receptive to copulation
• Female hears song through antennae

Question 8

Name the essential genes in fly courtship

Answer 8

Genetic hierarchy determines all aspects of sexual differentiation

The fruitless (fru) gene is essential for male sexual behaviour and is the first regulatory gene

Female behaviour is governed by fru and doublesex (dsx) genes

Question 9

Sex determination pathway in flies

Answer 9

sxl:
regulated splicing forms SXL protein in females
default splicing does not form SXL protein in males

tra:
regulated splicing forms TRA protein in females using SXL protein
default splicing does not form SXL protein in males

dsx:
regulated splicing forms DSX protein in females using TRA-2 protein
default splicing does form DSX protein in males

fru:
regulated splicing forms FRU protein in females using TRA protein
default splicing does form FRU protein in males

Question 10

What do female flies undergo regulated splicing?

Answer 10

They have XX chromosomes

Question 11

Mutant phenotypes

Answer 11

• dsx null mutants males carry out most aspects of song except one
• Expression of male dsx in females resulted into trandformation into males, but don’t carry out male courtship
• fru null mutant male flies phenotypically male, but show no courtship
• Less severe fru mutants alleles and ellelic combinations produce males that display defects in different stages of courtship