1 / 13

# Chapter 3: The Modern Synthesis - PowerPoint PPT Presentation

Chapter 3: The Modern Synthesis. Hardy-Weinberg equilibrium. If no selection and mating is random (i.e., no processes acting to change the distribution of genotypes), then the genotypes of F 1 (daughter generation) should be the same as the genotypes of F 0 (parent generation.

Related searches for Chapter 3: The Modern Synthesis

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Chapter 3: The Modern Synthesis' - warwick

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Chapter 3: The Modern Synthesis

• If no selection and mating is random (i.e., no processes acting to change the distribution of genotypes), then the genotypes of F1 (daughter generation) should be the same as the genotypes of F0 (parent generation.

• 1 = p + q (p = dominant, q = recessive)

• 1 = p2 + 2pq + q2 (square both sides)

• 1 = AA + 2Aa + aa

• Genotype ratio of 1:2:1

aa = 0.5 X 0.5 = 0.25

0.5

0.5

0.5

Aa = 0.5 X 0.5 = 0.25

aA = 0.5 X 0.5 = 0.25

0.50

0.5

0.5

0.5

AA = 0.5 X 0.5 = 0.25

• In a population of 100 we have 25 blue eyed people

• Since the allele for blue eyes is recessive then the blue eyed people are “aa” (q2)

• 25% or .25 are “aa”

• The frequency of the allele for blue eyes = the square root of .25 = .50 (50%)

• Since p + q = 1, the allele for Brown also = .50 (50%)

• In a population of 100 we have 16 blue eyed people

• Since the allele for blue eyes is recessive then the blue eyed people are “aa” (q2)

• q2 = 16/100 or .16

• The frequency of the allele for blue eyes = the square root of .16 = .40

• Since p + q = 1, the frequency of the allele for Brown eyes is .60 (60%)

• The F1 population 300 of which 27 blue eyed people

• Since the allele for blue eyes is recessive then the blue eyed people are “aa” (q2)

• q2 = 27/300 = .09

• The frequency of the allele for blue eyes = the square root of .09 = .30 (30%)

• Since p + q = 1, the allele for Brown = .70 (70%)

• The frequencies of the alleles for eye color in F1 are not the same as in F0 therefore evolution is taking place (selection or mate choice has changed the distributions)

• If the phenotype is result of multiple genes each having an additive effect.

• Example: tallness is controlled by 3 different genes each with 2 alleles (one for tall and one for short)

• If you get the tall allele in from all 3 genes then you get 6 tall (++++++) and you are the tallest, if you get all short you get 6 short (------) and you are the shortest.

• But if you get half of each you are in the middle (+-+-+-), you are also in the middle if you get ++-+--).

Since all allele effects are additive (all get expressed), the you can have any combination of 3 tall and 3 short and have the same phenotype

++++++

+++++-

++++--

+++---

++----

+-----

------

Tall

Short

Hidden Variation the you can have any combination of 3 tall and 3 short and have the same phenotype

• Multiple gene effects mean that natural selection and/or mate choice is not always favoring or selecting against the same genes

• Genes can hide in the recessive state when phenotype is dependent on multiple genes (loci).

Phenotypic Plasticity the you can have any combination of 3 tall and 3 short and have the same phenotype

• Soapberry bugs and mate guarding

• Frequency dependent strategy (Oklahoma population), trait is plastic

• In Florida sex ratios are stable and trait is canalized

Other terms the you can have any combination of 3 tall and 3 short and have the same phenotype

• Pleiotrophy = genes effect more than one trait

• Correlated response = phenotype is dependent on more than one gene, therefore selection for a trait effects frequency of multiple genes at the same time