Chapter 4 Flashcards LifeSci 2D03

QTL mapping for aphid feeding behaviour

• researchers used QTL mapping to determine the amount of genes involved in plant-choice in aphids

• researchers discovered two types of aphids

a) aphids that consume alfalfa

b) aphids that consume clovers

• researchers made F1 F2 generations by crossing individuals from both races

• measured the amount of time spent searching for plant, time on plant before penetrating it, and time spent digesting sap from plant

• researchers assessed the genotype of each individual, by using poly markers

Results

• found one to three QTL's

• not much variation

The phenotypic similarity between offspring and parent depends on...

• the additive effect of the alleles, contributed by both parents

• both parents only contribute one allele per locus (total of 2 alleles per locus)

• all alleles must have a similar effect on phenotype

Narrow-sense heritability

• measure of heritability most commonly reported

Variation in phenotype, like behaviour and morphology are due to differences in _____________________

• an individuals genotype and environment

Behavioural genetics

• looks at how genes and the environment contribute to the variation in phenotype amongst individuals

• by partitioning these effects

An individuals phenotype is a result of 3 factors...

• genotype (G) at different locations on a chromosome that effect behaviour

• environment (E), the individual has experienced

• gene-environment interactions (GxE),

—> environments may present challenges, and individuals genes affect how the individual will respond to these challenges

Equation of phenotypic variation

Vp = Vg + Ve

• Vp represents phenotypic variation

• Vg represents variation in genotype

• Ve represents variation in environment

Heritability (H^2)

• proportion of phenotypic variation in a population that's due to genetic variation

Broad-sense heritability

• is a part of heritability (H^2)

• includes all genetic effects on phenotype (genes, gene-environment..)

3 types of genetic effects on phenotype

• additive effects (A) , all individual alleles in genotype, have an effect on phenotype

• dominance effects (D), interaction between alleles at a locus, where one allele is expressed over the other

• epistatic effects (E), interaction between genes at different loci, such that one gene modifies another, or acts with it to make a new phenotype

Variation in genotype equation

Vg = Va + Vd + Vi

The proportion of phenotypic variation, solely due to additive effects is referred to as...

• narrow sense heritability (h^2)

Non-additive effects

• dominance and epistatic effects

• these effects involve interactions between alleles and are dependent

• influenced by alleles present in each generation

Additive effects

• independent of other genes or the environment

• primary importance for determining how a trait will respond to selection

Greater narrow-sense heritability means...

• the more an offspring should resemble it's parents

• due to more additive effects, all having a similar effect on phenotype

Narrow-sense heritability can be determined by...

• examining the similarity between parent and offspring

(parent-offspring regression analysis)

In parent-offspring regression...

• parents trait values are plotted against offspring trait values

• the more similar these trait values between parent and offspring, the more they resemble each other

Higher slope values in parent-offspring regression indicate...

• greater proportion of phenotypic variation is ADDITIVE VARIANCE

• which is, variance passed on from parent to offspring

Lower slope values in parent-offspring regression indicate...

• less proportion of phenotypic variance is additive variance

• and traits between parents and offspring are not so well transmitted

• more non-additive and environment variance is expressed, rather than additive

Evidence for genetic-based behaviour came from...

• captive animals

• and instinctive, innate behaviours

Lab strains on mice and rats

• researchers reasoned that since individuals in captivity experience the same conditions

• then, any differences in behaviour is most likely a result of variation in genotype

Instinctive, Innate behaviours

• behaviours that are performed the same way each time

• once initiated, will go to completion

• are present in individuals raised in isolation

• includes reflexes, involuntary responses to external stimuli

BUCK

• dog that suffered paralysis on the right side of his face

• blink response was absent on his right eyelid, while still functioning on his left eyelid