Why Does Evolution Have To Involve The Change Of The Genetic Makeup Of A Population Over Time?

Introduction and Learning Objectives

So far, nosotros take talked near the behavior of genes that are passed from ane generation to the next, focusing on the genotypes and phenotypes of individuals. At present we'll take a broader expect at genetics and see how the genetics of populations are studied. As yous will larn, evolutionary change takes identify through changes in the genetic composition of a population. The field of population genetics spans the disciplines of genetics and evolution. Past the end of this tutorial you should accept a working agreement of:

The definition of a population
How genetic variation in a population is studied
The Hardy-Weinberg equation
The factors that influence changes in allele frequencies
How the founder effect and bottleneck issue relate to genetic drift
How gene menses, mutations, and mating behavior can affect genetic stability
How selection tin influence allele frequency

Performance Objectives

Depict the assumptions of a population in Hardy-Weinberg equilibrium
Utilize the appropriate Hardy-Weinberg equations (allele and genotype frequencies) to solve population genetics problems
Summarize how the factors that can cause a population to motility abroad from HW equilibrium lead to evolution
Hash out how both a population clogging and a founder consequence tin lead to genetic drift, and its upshot on allele frequencies
Describe how mutation can be a source of new alleles in a population, and why some mutations can exist neutral, rather than harmful or beneficial
Illustrate how migration can affect the genetic structure of a population
Explain why non-random mating can change the genotype frequencies in a population, merely not the allele frequencies

Population Genetics

A population is a group of organisms that are members of the same species and that alive in the same geographical area. While natural selection occurs at the level of the private, through variations in fitness amongst individuals, development occurs at the population level. The reason for this is demonstrated in the post-obit table:

	Private	Population
Life Span	Ane generation	Many generations
Genetic Label	Genotype	Allele frequencies
Genetic Variability	None	Considerable
Evolution	None	Tin can change over fourth dimension

The genotype of an private is, for the most part, determined at the moment of fertilization and cannot exist changed during that individual'south lifetime. However, because populations are comprised of many individuals from different generations, the allele frequencies in a population can modify over time thus evolve. Population geneticists focus their studies in two areas. The showtime surface area is the measurement of genetic variation within a population. Morphological characters (due east.k., variations in length, weight, coloration) and molecular characters (e.g., variations in nucleotide sequences of Deoxyribonucleic acid or in amino acid sequences of proteins) are examined and quantified. The second area is the examination of the mechanisms by which genetic variation changes over space and time.

The evolutionary forces that tin can influence allele frequencies will be examined in the next tutorial. In this tutorial we volition examine how allele frequencies are used to make predictions about the genotypes of a population.

Table Reference: Afterward Table 20-one in Strickberger, M.W. 1996. Evolution. Second Edition. Jones and Barlett, Sudbury, Massachusetts.

Genetic Variation

Population geneticists measure the amount of genetic variation plant inside a population. Variation can exist measured within a population and betwixt populations. When there is no variation among the members of a population, the population is monomorphic for that particular graphic symbol; monomorphic means that simply one class exists. For example, the population of squirrels (Sciurus carolinensis) on the Penn State campus is monomorphic for coat color; all of the squirrels in this population have greyness fur.

Nonetheless, this is not true of all squirrel populations. At Kent Land, the squirrel population is polymorphic for fur colour (i.e., they take either gray or black fur, Figures 1 and ii).

Variations in some populations for a given grapheme can be farthermost (for case, the variation of shell colors in a species of Caribbean snail, Figure 3).

Other factors, besides genetics, can contribute to the variation of a character inside a population. For example, phenotypes can be affected past the environment. When you spend a lot of time in the dominicus, your skin becomes darker than the color that is determined past your genotype. As you learned, the genetic disorder PKU can be suppressed past diet. Other examples of environmental alterations are all around us. No two trees look exactly akin because branching patterns and leaf and limb numbers can be influenced by light, water, and food availability. In humans, IQ and size take been linked to diet in babies and immature children.. In short, the environment can influence how genetic information is expressed.

Figure 1. Gray Squirrel. (Click paradigm to enlarge)

Figure 2. Black Squirrel. (Click image to enlarge)

Figure three. Snail Shells. (Click image to enlarge)

The Genetic Composition of a Population

In previous tutorials we examined the genotypes of individuals and how they relate to the phenotypes expressed in subsequent generations. Go on in mind, the genotype of an individual becomes stock-still the moment that 2 gametes unite to form the diploid zygote (disallowment mutation). Still, a population consists of a group of individuals that may differ genotypically from one some other. How do we depict the genotype of a population?

The genetic makeup of a population tin be described by the frequency of alleles that be in that population. This is typically expressed as a fractional equivalent of ane. In other words, a population that has merely one allele for a detail gene has an allele frequency of i for that allele. If two or more alleles for a detail gene exist, so each has an allele frequency that is some fraction of one (nevertheless, all of the allele frequencies must add up to one). In the example of cystic fibrosis, the major CF allele is constitute at a frequency of 0.04 (four%) in Caucasian populations. This means that the wild-type allele is institute at a frequency of 0.96 (96%). Note that 0.96 + 0.04 = 1. Although the number of alleles may be quite variable (some genes accept dozens of alleles), the unproblematic arithmetics relationship all the same applies; that is, the frequencies of alleles for a given cistron must add up to one.

Obviously a population can have many genes for which alternative alleles exist. In the human species, about 30% of all genes have ii or more alleles. In other words, 70% of the genes are fixed (accept an allele frequency of one), whereas 30% of the genes have allele frequencies less than one.

Probability and Populations

How are allele frequencies actually determined? The Hardy-Weinberg equation can be used to summate allele frequencies. For example, allow's use the equation to PKU illness and designate the PKU allele "q," and the wild-type allele "p." What is the allele frequency for the PKU allele?

The frequency of individuals who are homozygous for the PKU allele in a population is q X q = q². Y'all should recognize this as the Rule of Multiplication. Yous should also know that q^two represents the PKU-affected individuals in the population because they are homozygous for q. The frequency of individuals who are homozygous for the wild-type alleles (the p allele) in a population is p X p = p^two. The frequency of individuals who are heterozygous in a population (PKU carriers) is p X q = pq. Notation, there are two ways to become this final calculation (depending on which parent donates the q allele); therefore, the Dominion of Add-on is also used to compute the odds of existence heterozygous (pq + pq or 2pq).

In a population, the frequency of PKU individuals who are homozygous for the allele + those who are heterozygous for the allele + those who are homozygous for the wild-type allele = 1. In other words, p² + 2pq + qⁱⁱ = ane. This is the Hardy-Weinberg equation for genotypes. (You lot may also recognize this equally a binomial expansion.) Before going on, be sure you empathize what these terms represent.At present, let'southward solve our original PKU trouble. Restated, what is the allele frequency for the PKU allele (q)? Nosotros know that the phenotypic frequency of PKU affliction is ane:10,000 or 0.0001. Think that this is the phenotypic frequency, only we want to determine the allele frequency for the PKU allele (q). Recognize that qⁱⁱ is the phenotypic frequency (afflicted individuals) in the Hardy-Weinberg equation. Therefore, the square root of the phenotypic frequency volition equal the allele frequency of the PKU allele. The square root of 0.0001 is 0.01.

Considering the wild-type allele (p) + the PKU allele (q) must equal one (p + q = 1), we tin can determine the wild-type allele frequency. ane.0 - 0.01 = 0.99 = wild-type allele frequency.

Applying the Hardy-Weinberg Equation

Now let's try a problem using the squirrels from Kent Land, which were described earlier in this tutorial. Have out a piece of paper and piece of work along with the post-obit description. The primal to agreement the equation is writing it out yourself.

Suppose that you have decided to visit Kent State for the weekend to encounter these squirrels for yourself. Yous want to decide the frequency of black (B) and gray (b) alleles in the squirrel population. Since it is not possible to see all of the squirrels on campus, yous decide to count 100 squirrels and use this as your sample to determine the allele frequencies. By the finish of the day you have scored 100 squirrels; 84 were blackness and 16 were gray. Next y'all need to use the Hardy-Weinberg equation to determine the frequency of these 2 alleles in this population. At first you make up one's mind that the allele frequencies are 0.84 for the B allele and 0.16 for the b allele. Is this correct? Are you overlooking something? When yous come across a blackness squirrel, what is its genotype? Black squirrels are either BB or Bb. And so some black squirrels are carrying the b allele. Black is a complete dominant, therefore, there is no manner to tell which squirrels are heterozygous for this allele.

Since you do not know if a black squirrel has a BB or Bb genotype, you cannot use the number of black squirrels to determine the frequency of the blackness allele. Just what about gray squirrels? Since grey is recessive to black, all of the gray squirrels are genotype bb, or they represent the q² value in the p² + 2pq + q² equation. Suddenly this is looking much easier. If q² = 16/100 = 0.16, then q = the square root of 0.16 = 0.iv. Since p + q = i, then 1 - q = p, so one - 0.4 = 0.six = p. Then the frequency of the black allele (B) is 0.6 and the frequency of the gray allele (b) is 0.iv. Now that you have this data, you can estimate the frequencies of the different genotypes in the population: BB, Bb and bb.

Effigy iv. Black Squirrel. (Click image to enlarge)

Population Genetics can be used to solve crimes!

Deoxyribonucleic acid fingerprinting is used in a variety of fields including agriculture, medicine, and historical investigations. Information technology has get especially useful in forensics, especially in criminal investigations.

A DNA fingerprint is created in a serial of steps:

DNA must be isolated - at a offense scene Dna tin can be isolated from blood, saliva, semen, hair or skin.
If the corporeality of DNA that is isolated is small-scale, PCR is used to amplify the isolated DNA (call up, you used PCR to dilate antibody resistance genes in bacteria when investigating the Salmonella outbreak at a chicken farm).
The amplified Deoxyribonucleic acid is then cut into pieces using special enzymes known as "restriction enzymes". Restriction enzymes cut Dna at precise sequences (for example, the restriction enzyme EcoR1 cuts Dna at the sequence GAATTC).
The DNA pieces are then run through a gel (using electricity); the smaller pieces travel further than the larger pieces. This creates a banding pattern that can be seen by fluorescing the Dna bands.
The pieces of DNA can be treated as alleles. If the frequencies of these alleles in the population are known, it is possible to summate the probability, using the Hardy-Weinberg equation, that ii unrelated people have the same set of alleles.

The DNA fingerprints below come from 3 sources – the victim of a tearing crime, DNA bear witness collected at the crime scene, and the primary doubtable in the crime. In that location are 4 different gene sequences shown. For each factor, if a single band is seen that indicates the private is homozygous for that particular gene. If two bands are seen, that indicates the individual is heterozygous.

Using the allele frequency information provided in the table below, calculate the probability that the Deoxyribonucleic acid from the crime scene belongs to the suspect.

Gene Sequence	Allele Frequencies
1	Allele 1 = .3, Allele two = .4, Allele three = .3
ii	Allele 1 = .4, Allele ii = .6
3	Allele i = .i, Allele two = .ix
iv	Allele 1 = .five, Allele 2 = .5

Multiple Alleles

All of the cases that we have examined have had a single gene with two alleles. But what about genes that take 3 or more alleles? This is dealt with in the same style, simply the determination of allele frequencies becomes a scrap more involved.

You lot previously learned about the human ABO blood group arrangement (Effigy v). This was used as an example of a cistron with multiple alleles (I^A, I^B, i) and codominance because both alleles are expressed in AB heterozygous individuals. The O allele (designated equally i) is recessive to the I^A and I^B alleles. Now we'll work a problem for a system with three alleles. In a human population, the I^A allele has a frequency of 0.iii and the I^B allele has a frequency of 0.ane. Pull out a piece of newspaper and a pencil and write downwardly these numbers.

Starting time, summate the frequency of the O allele. Remember, the allele frequencies for a detail gene must add upwards to one. At present that you have these three allele frequencies, make up one's mind the frequencies for all of the possible genotypes in the population. When y'all are finished, these should besides add up to one. If information technology is helpful, the H-W equation that you would utilise for iii alleles is p+q+r=1, and the equation for the genotypes is p²+ 2pq + q² +2pr +2qr + r² = 1.

Figure v. Multiple alleles for the ABO blood groups. (Click epitome to enlarge)

Using the Hardy-Weinberg Equation in Evolutionary Studies

You should now capeesh how the Hardy-Weinberg equation tin be used to report the genetic composition of a population. But how does this fit into evolution studies?

The answer is that changes in allele frequencies are the most fundamental indication that evolution is occurring in a population. If two populations of the same species have the same allele frequency for a given gene, it can be concluded that evolutionary forces are not operating on that gene (at least at that time). On the other manus, if the allele frequencies are dissimilar for a given cistron, then evolutionary forces may be operating on that population.

If allele frequencies remain stable betwixt generations, so the population is considered to exist in Hardy-Weinberg equilibrium.

Evolution and Population Size

From a geneticist's betoken of view, a population composed of hundreds or thousands of individuals is less likely to evolve than a minor population. The larger the population, the more of a buffer there is against random variations in allele frequencies; an space size population would exist nearly completely resistant to random fluctuations. In contrast, small-scale populations are especially vulnerable to the loss of genetic variability due to random events; in fact, they may evolve into extinction.

Development in Small Populations: Genetic Drift

Modest populations are much more than likely to feel genetic drift (random fluctuations of allele and genotype frequencies) than are large populations. If a population has an allele frequency of p = 0.25 or i/4, then the allele frequency of q is ane - 0.25 = 0.75 or 3/four. (Retrieve, the sum of all individual allele frequencies for a particular factor must add together up to i.) Therefore, for each p allele, there are 3 q alleles in the population (or a ane:three ratio). If a population consists of grand individuals and m X 2 = 2000 alleles, then 500 of the alleles in the genetic pool would be p (2 X 250) and 1500 of the alleles would be q (ii X 750). If the alleles in the side by side generation are counted, they may have drifted by five alleles (due east.g., to 505 and 1495), merely the new allele frequencies would be 0.253 and 0.748, which are very close to the original values of 0.25 and 0.75. Although there is very small measurable change, information technology would have many generations before one allele became fixed in the population and the other eliminated.

Nonetheless, if the population in the example above independent only 10 individuals (2 X x = xx alleles) and the initial allele frequencies were again p = 0.25 and q = 0.75, then in that location would exist five p alleles (2 X 2.5) and fifteen q alleles (ii X 7.5) in the population. If the next generation also drifted by five alleles, then there would be 10 p alleles (5 + 5) and 10 q alleles (15 - 5). Therefore, in 1 generation the allele frequencies would get from 0.25 and 0.75 to 0.five and 0.5. If both alleles are selectively neutral (have no result on fettle), and then each faces a probability of being lost in the course of several generations, and eventually one allele volition go fixed in the population. Heterozygosity at that factor would become zippo and the genetic variation inside the population would be reduced.

Next we'll examine the two major situations that restrict population size and atomic number 82 to genetic drift.

Genetic Migrate and the Bottleneck Result

One situation that tin result in genetic drift is the bottleneck outcome. A bottleneck event (east.grand., earthquakes, fires, over-hunting) decimates a population and results in only a small number of individuals surviving. In a bottleneck event, the remaining, random survivors may not have the aforementioned allele and genotype frequencies as the original population. In the new population, some alleles may be found at college frequencies, whereas others may be establish at lower frequencies or even lost birthday.

In a small but rapidly reproducing population, genetic migrate volition typically bear on the population for a number of generations until the population size becomes large enough that genetic drift is negligible. While natural disasters have historically been the cause of bottleneck effects, overzealous hunting can also cause this effect.

Many endangered species, such as the cheetah (Figure vi) and the American bison, provide examples of bottleneck events and reduced genetic variation. Among cheetahs, all living individuals are genetically very like, which means this surviving population has less genetic variation upon which selection can act. Even when a species, such equally the cheetah, is protected post-obit a clogging event, the loss of genetic variability may brand the species more likely to go extinct. Genetically homogeneous populations are more prone to catastrophes considering a given insult (e.k., a disease or a predator) can sweep through the entire population quickly; without variation, at that place is nothing for natural choice to human activity on. Therefore, conservation efforts must not just preserve numbers, they must also promote genetic variability. Only when some individuals are amend suited to the environs than others, can development increase the adaptation of a population to its environment. Perchance the potential to undergo natural selection is ane of the all-time measures of a healthy population.

Figure 6. Cheetah (Click image to overstate)

There is reason to call back that bottleneck effects might play a major part in extinction. There is evidence that major catastrophic events (e.g., meteor strikes) might take led to major clogging effects in Globe's past. Such events might not have necessarily killed off all members of a species (due east.g., dinosaurs), just might have decimated their population enough such that they became genetically weakened due to a loss in variability; eventually these populations died out. One book with a catchy title, Extinction: Bad Genes or Bad Luck? by David M. Raup, explores this thought.

Genetic Drift and the Founder Event

Another situation that can result in genetic drift is the founder issue. A founder event occurs when a few individuals (founding individuals) become geographically separated from the original population and form a new population. The alleles present in the founding individuals make up the genetic pool of this new population. Most likely, the founding individuals volition have the same allele and genotype frequencies of the original population, nor will they possess all of the variation present in the original population. Considering information technology will take several generations before their population increases much in size, genetic drift would continue to influence the allele frequencies in the population. This effect tin be seen when remote islands are colonized.

An example of the founder consequence in human populations occurred on the island of Tristan da Cunha (Figure seven). This island was settled in the 1800'due south by xv British immigrants. At that place have only been a couple of migrations since; today there are but seven surnames on this island that has nigh 250 inhabitants. Expectedly, this leads to bug associated with inbreeding (the mating of closely related individuals). I notable problem is the occurrence of retinitis pigmentosa (a rare form of incomprehension), which occurs at a much college frequency in this population than in the original population. Some questions in the tutorial quiz will use this genetic disorder to illustrate how the founder upshot alters the frequency of alleles in a modest human population.

Figure 7. The isle of Tristan da Cunha. (Click image to overstate)

The Founder Effect: Test Your Agreement

During the early on 1700's, a small group of pacifist Protestants fled Germany to avert religious persecution. This group, the Dunkers, settled in the farmland of eastern Pennsylvania and has been relatively isolated from other groups of people living in the expanse (they have strict rules about spousal relationship outside of the grouping). The original group was comprised of 50 families.

The current Dunker population is genetically distinct from the rest of the United States (and modernistic Germany) in terms of the ABO claret group arrangement. In the Dunker population, the frequency of the I^A allele is .30 (30%) and the frequency of the O claret type is .sixteen (16%). In the full general Us and German population the frequency of the I^A allele is .40 and the frequency of the O blood type is .25 (25%).

What are the frequencies of the I^B and i alleles in both populations?
Use your knowledge of the founder effect to explain the differences in ABO blood group allele frequencies between the two populations and bespeak whether or not this is an example of adaptive development.

Gene Catamenia

Populations remain genetically stable if no alleles enter or go out the population. Recall, a change in allele frequencies due to interactions with outside populations is termed gene flow. If a population was fixed for i allele at a gene and a gamete carrying an alternative allele was able to fertilize an individual from that population, then the allele frequencies would change due to the introduction of this new allele and the population would undergo development. Migration of individuals amongst populations leads to gene flow, as individuals immigrating into the population bring new alleles, while those emigrating have alleles with them.

Mutations

A mutation is a change in an organism'due south DNA. Mutation may introduce a new allele into a population, causing modest changes in the allele and genotype frequencies. Considering mutations are the ultimate source of all genetic variation, over time they can have a significant influence on the genetic structure of the population, simply the mutation rate usually is very low so it is not a strong evolutionary strength. In general, , most mutations institute in a population appear to be "neutral", having lilliputian to no event on the phenotype. Considering several dissimilar combinations of nucleotides may code for the aforementioned amino acid (recall the redundancy in the genetic code), a mutation in the Dna of a protein-coding factor may non change the amino acid sequence of the protein. Conversely, some mutations can have a major effect on the phenotype. These mutations most always effect in a nonfunctional or less efficient product Very rarely, a mutation may issue in a poly peptide that is slightly more efficient, or that performs a new function. In order for the frequency of the mutant allele to increase as a result of natural option, the advantage would have to be great plenty to affect the individual's reproductive success. Therefore, although an supposition when applying the Hardy-Weinberg equation is that no internet mutations occur, most mutations have little overall effect on the allele frequencies of a population.

Random versus Nonrandom Mating

Random mate selection favors genetic stability. Nonrandom mate selection often occurs in natural populations because an individual is more likely to cull a mate from his or her vicinity than from more distant areas of the population. Frequent nigh-neighbor matings tend to subdivide the population's factor pool into subpopulations that have less genetic multifariousness than the entire genetic pool of the population.

Inbreeding (the mating of closely related individuals) was described earlier in this tutorial. Cocky-fertilization ("selfing") occurs when an private fertilizes its own gametes (a common occurrence in plants). Both of these mating processes decrease the level of heterozygosity in the offspring. Normal salubrious individuals can carry several or many deleterious alleles. Although each individual may carry some deleterious alleles, unrelated individuals are likely to exist carriers of different harmful alleles. Therefore, virtually of the resulting offspring will be good for you carriers as well. If the parents are closely related, however, it is more likely that they are carrying the same deleterious alleles. Some of the recessive deleterious alleles will occur in the homozygous state, exposing the allele to selection.

Similarly, individuals may cull mates that have some of the aforementioned phenotypic traits (due east.g., body size or tiptop) as themselves. This is termed assortative mating. Although these kinds of characters are complex, involving numerous genes, they are still commonly heritable. Mating of genetically similar (although non necessarily related) individuals tends to increment the amount of homozygosity in the population. However, nonrandom mating does not change allele frequencies because information technology does not include introducing new alleles into the population, or the loss of alleles.

Genetic Stability and Selection Pressure

This tutorial has focused on how not-adaptive changes, some due to random events, can impact allele frequencies, thus affecting the genetic stability of a population. Even deleterious alleles may increment in frequency due to take chances events (call back the Tristan da Cunha example).

One of the conditions for maintaining Hardy-Weinberg equilibrium is that all individuals have the same reproductive capacity and fitness. Even minor deviations from this equality will lead to some individuals producing more offspring than others, leading to a alter in allele frequencies. Whatever alleles that direct or indirectly bear upon an individual'south ability to survive, mate, or reproduce may respond to selection pressure. Under stiff selection pressure level (e.g., when bacteria are exposed to an antibiotic), a mutation conferring some form of resistance to the antibiotic can increase in frequency in the population very quickly. In fact, antibiotic resistance is a major health concern, and both pesticide and herbicide resistance are important concerns to agriculturists. As you will learn, these examples of the evolution of resistance are a result of natural selection because the surviving, resistant individuals are ameliorate adapted to their surroundings.

Similarly, an allele that makes an individual more vulnerable to illness or predation is likely to be nether very strong choice pressure and may subtract in frequency very chop-chop, until it is either very rare in the population or purged completely from the gene puddle.

Summary

This tutorial covered the basic principles of population genetics. A population is a group of organisms that are members of the same biological species and that live in the same geographic expanse. Characters in a population can be monomorphic, showing no variation, or polymorphic, having at least two dissimilar variants. Variation can be caused by the organism'due south genotype or by environmental furnishings. The Hardy-Weinberg equation can exist used to examine genetic variation inside populations. In the case of two alleles for a factor, the sum of the frequency of the alleles equals 1 or 100%. This is represented by the equation p + q = 1. To determine the frequencies of the 3 possible genotypes, use the equation p² + 2pq + q² = 1. When the allele frequencies stay the aforementioned between generations, the population is in Hardy-Weinberg equilibrium. Hardy-Weinberg equilibrium requires that allele frequencies within a population remain the same from 1 generation to the side by side, as long as certain conditions (including no mutation, large population size, no migration, random mating, and no natural selection) are met. The next tutorial volition explore the evolutionary forces that can cause changes in allele and/or genotype frequencies in a population; that is, changes that lead to evolution.

The Hardy-Weinberg equation tin can be used to make up one's mind the allele frequency in a population. Thus, it provides a useful tool to depict the degree of evolution that is taking place over successive generations. Non all populations are undergoing evolution at all times. In certain stable environments, many populations show no evidence for evolution. (Although if the conditions modify, so evolution can take place.)

There are a number of conditions that predictably decrease development; namely: large populations that are more genetically stable compared to smaller populations; no migration/immigration past which new alleles are introduced or removed from a population; no mutations to innovate new alleles; random mating that allows all individuals equal access to all alleles and; no natural selection, which causes changes in allele frequencies due to fitness differences between individuals.

Conversely, opposing conditions increase evolution; namely: small populations are genetically unstable because they are susceptible to genetic migrate; migration/immigration that allows alleles to enter or leave a population; mutations that innovate new alleles; nonrandom matings that cause unequal access to all alleles; and natural choice that changes allele frequencies based upon individuals' reproductive capacity and fettle.

We will wait more specifically at natural selection in the next tutorial.

Terms

Later on reading this tutorial, you lot should understand the following terms:

assortative mating bottleneck effect founder effect gene catamenia gene pool genetic drift Hardy-Weinberg equation inbreeding monomorphic	mutation polymorphic population range species

Questions? Either ship your instructor a message through ANGEL or attend an LA part hour (the times are posted on Affections).