Sexual Selection/Molecular Evolution (W4-L2)

Question 1

Argument for Natural selction in comparison to Neutral Theory…

Answer 1

• Advantagous mutations are more common
• Molecular evolution will are dominated by selection
• No molecular clock

Question 2

Argument for Neutral Theory in comparison to Natural selection…

Answer 2

• Pseudogenes evolve very fast
• genes that have important functions should evolve slower
• synonymous codon positions evolve faster than non-synonymous sites adn should evolve with a constant rate (not always true)

Question 3

What is a psuedogene?

Answer 3

Dead genes that have no function and no fitness effect

Question 4

What is the concept of the Molecular Clock?

Answer 4

concept that the rate of molecular evolution is pretty constant

Exceptions:

• different protiens have different rates
• different domains of the same protein may have different rates
• same protein in differnet organisms may have differnet rates

Question 5

What is the Nearly Neutral Theory?

Answer 5

Discovered by Tomoko Ohta

Suggests most muation events at the molecular level are slightly deletrious rather than strictly neutral

Small populations: drift dominates and slightly deletrious mutations are neutral (fix relativly quickly)

Large populations: seletion is more pronounced

Question 6

What is the Ka/Ks test?

Answer 6

Method used to detect postive selection; suitable for between species

Ka=nonsynonymous
Ks=synonymous

Purifying (negative) selction: ka/ks=0
Neutral selection: ka/ks=1
Positive selction: ka/ks > 1

Question 7

What is the Mcdonald- Kreitman test?

Answer 7

Method used to compare divergence between two species with polymorphism within each species

Proved that positive selection exists after acceptence of neutral theory in the 1990s

Question 8

What is sexual selection?

Answer 8

Selection for traits that increase reproductive output/likelyhood of obtaining a mate

Slection in relation to reproduction not survival

Question 9

Bateman’s principal

Answer 9

Imbalance generatedfrom fundamental differences in investment in gamates

Females produce fewer large gamates whereas males produce many ‘cheap’ gamates

Causes intra and inter selection

Males maximize fitness by reproducing more
Females maximize fitness by selecting ‘better’ males

Question 10

What factors make a ‘good’ mate?

Answer 10

• condition
• good at avoiding predation
• liklihood to productive attractive offspring
• high investment in offspring