Biotechnology applications

• If I was taking the AP test, I would be sure to know about… – Stem Cells: and the controversy – Application of biotech such as • 416-423 • Diagnosis of disease • Gene therapy • Development of drugs • Forensics and paternity – Short tandem repeats (STRs) • Environmental clean-up • Genetically modified organisms.

Charles Darwin

Pre-Darwin

Lyell:

Geology, Uniformitarianism  very old earth.

Malthus:

Exponential Population Growth

LaMarck:

Evolution. Inheritance of acquired characteristics (wrong, but still evolutionary)

The Voyage of the

HMS Beagle

Natural Selection

Observation 1

: Variation

No two organisms are completely alike.

Observation 2

: Reproduction…

…And overproduction

Inference 1

: Differential “fitness” in the environment due to variations.

The “struggle for existence”

Inference 2

: Over the span of geological time (billions of years), inheritance of adaptations will lead to evolution of the population.

Fundamental Conclusions

1. To develop the diversity of life seen on the Earth today, the Earth has to be incredibly old.

2. If organisms evolve from pre-existing organisms, then all organisms should share a universal “

common ancestor

”

“tree thinking”

Unsettled by Darwin

1. Origin of Life 1. Origin of species 1. Nature of variation/inheritance

1.1: Natural selection is a major mechanism of evolution 2. THE MODERN SYNTHESIS

The “Modern Synthesis”

Connects Darwinian evolution to genetics and modern understanding of inheritance.

Where Traits come from:

Trait

Variation comes from Mutation

Mutation

: A change in a DNA sequence. Happens spontaneously and unavoidably.

Mutations create “alleles”

Alleles

: Different versions of the genes for a trait.

Evolution Defined:

Evolution

: Changes in allele frequencies over time.

Ex. Galapagos Finches

Grant and Grant

: Studied the finch population on an isolated island in the Galapagos. Measured the beak dimensions of all birds on the island every year for decades.

Connected changes in beak dimensions to fluctuations in the environment (precipitation, seed sizes)

Evolution Misconception Alert!

Misconception

: Individuals evolve.

Evolution is a “population level” phenomenon. Individuals DO NOT evolve! The evolution of a population emerges from the individual fitness of members of that population. As they survive and reproduce or not, the frequencies of alleles in the next generation will change accordingly.

Pg. 468-475

• Watch Bozeman science on Hardy Weinberg calculations

Evolution

• Changes in the genetic makeup of populations overtime • Changes in the genetic makeup lead to changes in phenotypes- variation • Favorable variations for a particular environment are known as adaptations

Microevolution and Macroevolution

• Microevolution refers to the changes in the genetic makeup over time • Macroevolution refers to the origin and extinction of species and that fuel the diversification of life

• Populations evolve, individuals do not • Population- a group of individuals of a single species that live and interbreed in a particular geographic area at the same time

Gene Pools and Gene Frequencies

• Gene Pool- the sum of all the alleles in a population; the sum of the genetic variation within a population • Allele Frequency- the proportion of each allele in the gene pool • Genotype Frequency- the proportion of each genotype (homozygous dominant, heterozygous, homozygous recessive) in a population

Hardy-Weinberg Theorem

• Describes the gene pool of an idealized, non evolving population to which others may be compared • States that the frequency of alleles and genotypes in a population’s gene pool remains constant from generation to generation provided that only Mendelian segregation and recombination of alleles are at work

Evolution vs. Genetic Equilibrium

To understand how populations evolve over time, scientists find it helpful to determine what happens when no change takes place… Genetic Equilibrium Hardy-Weinberg principle: Allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change.

5 conditions are required to maintain genetic equilibrium… If conditions are not met, the population will evolve.

REVIEW!!!

What is genetic drift?

A population’s gene pool has to be kept together and separate from the gene pools of other populations

No selective pressures!!

Conditions of Hardy-Weinberg Equilibrium

1. The population size is extremely large 2. There is no gene flow occurring (no movement of individuals into or out of the population) 3. There is no mutation 4. Random mating occurs 5. There is no natural selection acting on the population

• Any departure from the five conditions usually results in evolution

Two major uses for scientists

• Useful for predicting the approximate genotype frequencies of a population from its allele frequencies • Allows biologists to evaluate which mechanisms are acting on the evolution of a particular population

Hardy-Weinberg Equilibrium

p 2 + 2pq + q 2 = 1 • p represents the frequency of one allele (usually dominant) • q represents the frequency of the other allele (usually recessive) • p 2 represents the frequency one homozygous genotype (usually homozygous dominant) • q 2 represents the frequency other homozygous genotype (usually homozygous recessive) • 2pq represents the frequency of the heterozygous genotype

• Frequencies are usually given as percentages, but should be converted to decimals to work the problems; move the decimal 2 places to the left • The frequency of p and q must also equal 1: p + q = 1

Solving Hardy-Weinberg Problems

• Examine the question to determine what piece of information you have been given about the population. In most cases, you will be given the percentage or frequency of the homozygous recessive

phenotype

or homozygous dominant

phenotype

– Remember that genotype and phenotype are not the same • The recessive phenotype represents the genotype q 2 always • The dominant phenotype represents the combination of the p 2 genotype and the 2pq genotype

• The first objective is to find out the value of p or q. If this is achieved, then every other value in the equation can be determined by simple calculation. • Take the square root of q 2 to find q • Determine p by subtracting q from 1 • Determine p 2 by multiplying p by itself • Determine 2pq by multiplying p times q times 2 • Check that your calculations are correct by adding up the values for p 2 + 2pq + q 2 (the sum should equal 1 or 100%)

Example Problem: In the Caucasian American population approximately 70% of people can taste the chemical phenylthiocarbamide (PTC), the dominant phenotype, while 30% are non-tasters, the recessive phenotype. Determine the frequency of : The homozygous recessive phenotype (q 2 ): The dominant allele (p): Homozygous tasters (p 2 ): Heterozygous tasters(2pq):

Darwin’s Observations

• • • • Resources are limited Organisms will fight or struggle for resources Variation in organisms leads to differential success Those organisms that are able to survive and reproduce will pass their characteristics on to the next generation

Defining “Survival of the Fittest”

• • • Fitness refers to the best adapted individuals for a particular environment Survival refers to the ability to not only live, but reproduce, thus passing on adaptive traits to the next generation LINK IT TO GENES!!!

– Favorable phenotypes don’t just appear – Favorable mutations to genes result in adaptive phenotypes

Darwin’s Ideas

• • On The Origin of Species By Means of Natural Selection Major points of Darwin’s Theory: – Species are not constant, they change over time (evolve) – All species share a common ancestor – The mechanism that produces changes in a species is natural selection • • Natural Selection: The differential survival and reproduction of individuals in a population based on variations in their phenotypes