Week 5 Flashcards
What is an example of key genes being different in different populations of closely related species?
Humans, Apes, Howler monkeys, Old World monkeys trichromatic -They have 3 receptors in their retina allowing them to see all colours
New World monkeys dichromats and trichromats - every animal has the blue opsin, but red and green are encoded on separate X chromosomes
Why are Humans, Apes, Howler monkeys, Old World monkeys trichromatic?
Blue receptor gene is autsomal
X chromosome has both red and green
What can happen in Humans, Apes, Howler monkeys, Old World monkeys impacting being trichromatic?
XY = single allele – mutations are exposed
XX = “back-up” allele
XY more likely to have dichromatic mutations causing colour blindness
Why are new world monkeys dichromates and trichromates?
XY = always dichromatic blue autosomal AND (red or green) x chromosome
XX = can be dichromatic OR trichromatic
How did they test for the advantage to being trichromatic compared to dichromatic?
They got trichromatic and dichromatic marmosets and spread pink and green kix cereal on the ground.
They then recorded how well each monkey did at collecting the number of cereal
Then the did PCR to amplify the opsin region and sequenced the amplified DNA
What were the results of the experiment of trichrimates and dichrimate marmosets?
Both groups found green kix around the same trichromates slightly more
Dichromates found green and red kix about the same
Trichromates found pink kix a lot more than dichromatic marmosets
What conclusions can be drawn from this experiment about tri vs dichromates?
There is a definite link between being trichromatic and being able to distinguish orange/red food
In the forest the red fruit is the ripe fruit and therefore the ability to better distinguish red is advantageous
This provided an adaptive explanation for trichromatic colour vision
Why are there still dichromatic monkeys if being trichromatic is advantagous?
It would require a chance mutation restructuring an entire chromosome
What are the different behaviours for fruit fly feeding behaviours and what encoded for it?
Rovers = 70% of population
Sitters = 30% of population
Due to differences in the gene ‘foraging’
forR is the dominant allele
fors is recessive
Could fruit fly feeding behaviours change based on the environment?
However, rovers can become sitters, and vice versa given certain environmental conditions
So genetically encoded ‘innate’ behaviours can be variable, just like learned behaviours
What is an parenting behaviour in male Three-spined stickleback (Gasterosteus aculeatus)?
During breeding season, males defend territories, construct nests and attract mates
Females spawn in the nests
Males are the sole providers of parental care – they defend and tend their fertilised eggs
An important behaviour is “fanning” – oxygenates eggs
What can change male stickleback parenting behaviour?
Males adjust their care in response to many environmental factors – diet, algal blooms, temperature, oxygen availability, clutch size etc.
However, males show consistant individual differences in fanning behaviour
What is heritability?
The extent to which phenotypic variation in a population can be attributed to individual genetic differences
What is the heritability equation?
h^2 = V(inverse ^)A / V (inverse ^)P
What do each of the letters in the heritability equation mean?
h^2 = this is just the symbol for heritability, nothing is being squared! The value is always between 0 and 1
VA = additive genetic variance (variation in genotype)
VP = total phenotypic variance (variation in phenotype) (VP = VA + VE)
What happens if phenotypic variance is 0?
If there is no phenotypic variation, you can’t calculate heritability. The concept just doesn’t exist as you cant divide by 0
What happens if VE = 0 (identical environments)?
Identical environments –> 100% of trait variation attributed to genetics –> Heritability = 1.0
VP = VA + VE VE = 0 so VP = VA
