Population indicators: Gene pool - totality
population genes
Indicators
populations:
number;
density - population size,
per unit area;
fertility;
mortality;
age structure;
distribution in space;
growth curve, etc..

population genetics

STE (synthetic theory of evolution)=

Darwinism and STE

Allele frequencies

Hardy-Weinberg Law

Allele frequencies

Genotype frequencies

Task

Solution

Because the,

Some hereditary metabolic defects and frequencies of recessive homozygous and heterozygous genotypes

Heterozygous individuals, normal in phenotype, but possessing a recessive gene, which in the homozygous state can cause a disorder

Sickle cell anemia

FACTORS CAUSING CHANGES IN POPULATIONS

MUTATION PROCESS

NON-RANDOM CROSSING (sexual selection)

POPULATION WAVES

DRIFT OF GENEES

“Only the spring waters will rush in, and without that they are dying in the hundreds...” Nekrasov

The founder effect is another cause of genetic drift. In this case, several individuals (or even one, but pregnant) colonize a new place

An example of the founder effect in humans:

Frequency of the B allele according to the AB0 blood group system in human populations

INSULATION

environmental insulation

Another example of ecological isolation: Big rattle weed: 2 races arose according to the timing of flowering - before and after mowing. The races have flowers of different sizes

Types of reproductive isolation

Isolation in humans

Thus, during microevolution:

Population is a collection of individuals of a given species, inhabiting a certain space for a long time (several generations), consisting of individuals that can freely interbreed with each other, and separated from neighboring populations by one of the forms of isolation (spatial, seasonal, physiological, genetic, etc. .).

A genetic population (panmictic, freely reproducing) is a group of animals or plants of the same species, inhabiting a certain territory, freely reproducing sexually, subject to the real possibility of crossing any male with any female, combining any gametes (gene alleles) of the same sex with any gametes (alleles) genes) of the other sex within their group.

Panmixia conditions: 1. Free reproduction 2. Complete absence of natural and artificial selection 3. All individuals are viable, fertile and leave the same viable fertile offspring 4. No migration of individuals 5. Absence of mutation process

A genetic population is a model that allows you to trace the genetic processes occurring in any really existing population: 1. Determine the actual genetic structure of the population 2. Determine the level of distribution of hereditary diseases in the population 3. Study what patterns the frequency of occurrence of various genotypes obeys 4. Determine the paths of evolution of populations

Properties of a genetic population: Plasticity of the genetic structure, changing under the influence of factors of natural and artificial selection The ability of the genetic structure of the population to adaptively respond and change when changing environmental conditions Preservation of the general genetic structure corresponding to environmental conditions and the manifestation of genetic homeostasis due to the presence of the adaptive abilities of this structure Ability to unlimited evolution

Calculation of genotype frequencies (example 1). 4200 people were examined using the MN blood group system. have antigen M, 882 people. have antigen N, 2100 people. have M and N antigens. The frequency of the MM genotype is 1218:4200 (29%) The frequency of the NN genotype is 882:4200 (21%) The frequency of the MN genotype is 2100:4200 (50%)

Calculation of allele frequency in heterozygotes (example 2) If a population consists of 30 heterozygous individuals (Aa), therefore there are only 60 alleles (A+a) in the population, including 30 “A” and 30 “a”. The frequency of the dominant allele is denoted by p, and the frequency of the recessive allele by q. pA= A/(A+a) = 30/60 = 0.5 qa= a/(A+a) = 30/60 = 0.5 pA + qa = 0.5+0.5 = 1

Calculation of allele frequency in a heterogeneous population (example 3) It is required to determine the frequency pA and qa if the population contains 64% AA, 4% aa, 32% Aa. The total number of alleles is taken as 100%, then in the population 64% of the AA individuals have 64% of the A alleles, 32% of the Aa have 16% of the “A” alleles and 16% of the “a” alleles pA = 64%+16% = 80% (or 0 ,8) qa = 1 – pA = 100% - 80% = 20% (or 0.2)

Hardy-Weinberg Law If in a population the gene “A” occurs with a frequency p, and its allele “a” with a frequency q, and p + q = 1, then under the condition of panmixia, an equilibrium of genotypes is established in the first generation, which is maintained in all subsequent ones generations; equilibrium is expressed by the formula: p 2 AA + 2pqAa + q 2 aa = 1

Solution to problem 1 p 2 AA + 2pqAa + q 2 aa = 1 By condition q 2 aa = 16% = 0.16 Therefore qa = 0.4 Hence pA = 1 - qa = 1 – 0.4 = 0.6 Structure of the original population looks like this: 0.6 2 AA + 2×0.6×0.4Aa + 0.4 2 aa = 1 0.36AA + 0.48Aa + 0.16aa = 1

As a result of the rejection of all recessive homozygotes, the population is reduced to a value of 0.84, because 1 – 0.16 = 0.84, and the decrease was due to recessive genes. Consequently, the relationship between pA and qa has changed towards increasing pA. To determine the new concentration pA and qa after rejection, it is necessary to carry out the following transformations:

To determine the genetic structure of the population of the next generation, we substitute the new values ​​of p and q (pA = 0.7, qa = 0.3) into the formula of the Hardy-Weinberg law: p 2 AA + 2pqAa + q 2 aa = 1 0, ×0.7 ×0.3 + 0.3 2 = 1 0.49 + 0.42 + 0.09 = 1

Theoretical frequencies in accordance with the Hardy-Weinberg law should have the following values: p 2 AA + 2pqAB + q 2 BB = 1 0, ×0.825×0.175 2 = 1 0.68 + 0.29+ 0.03 or = 100

Actual series: =100 Theoretical series: =100 Based on a comparison of the actual and theoretical series of numbers, the conclusion arises that there is no equilibrium in the population, because in the actual series, in comparison with the theoretical one, there is a lack of homozygotes (AA and BB) and an excess of heterozygotes (AB).

Pearson's goodness-of-fit criterion allows you to compare the actual series of numbers with the theoretical ones and answer the question about their correspondence (or non-correspondence) to each other. Where 0 – actual frequencies E – theoretical frequencies If χ 2 = 0, then there is complete correspondence of the actual splitting to the theoretically expected one. When χ 2 actual > χ 2 theoretical the differences are significant χ 2 theoretical differences are significant">

χ 2 = (65-68) 2 /68 = 36/29 + 9/ = 4.37 χ 2 table. = 5.99 Therefore, the conclusion is not reliable, there is an equilibrium.

Effect of mutations Let's assume pA = 1, qa = 0 Gene “A” mutates into “a” with frequency = 0.00003 Reverse mutations with frequency 0.00001 Let us accept the notation: U – probability of direct mutations W – probability of reverse mutations Change in frequency of allele A in population per generation will be

If in the original population p = 0.8 and q = 0.2, then the change per generation will be: 0.2 × 0.00001 – 0.8 × 0.00003 = -0, therefore the frequency of allele A in the next generation will decrease to 0.799978, and the frequency qa will increase to 0.200022

The example shows that with different probabilities of direct and reverse mutations of a gene in a population, the frequency of the allele of this gene in the direction of which mutations are more likely to occur will increase. However, the change in the ratio of allele frequencies in the population due to such mutational pressure goes only up to a certain limit, at which the number of direct mutations occurring becomes equal to the number of reverse mutations, i.e. when Wq = Up

Slide 2

Let's think 2

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Problematic question:

Is a population or a species the elementary unit of evolution? 3

Slide 4

SpeciesSubspecies

Populations Pack Herd Pride (herd) (family) 4

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The term population was introduced in 1903. Johansen

To designate a genetically heterogeneous group of individuals of the same species, in contrast to a homogeneous pure line 5

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Review the following population definitions:

A collection of individuals of the same species, occupying a separate territory within the range of the species, freely interbreeding with others, and isolated to varying degrees from other populations of this species. Any collection of individuals of the same species capable of self-reproduction, more or less isolated in space and time from other similar populations of the same species. A collection of individuals of the same species that have a common gene pool and occupy a certain territory. A collection of individuals of the same species that inhabit a certain space for a long time, and within which panmixia (crossbreeding) occurs to a certain extent and is separated from other populations by some degree of isolation. 6

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Use the available material to formulate the concept - population

Population (from Latin Poрulos – people, population) - 7

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Population characteristics

Ecological: Evolutionary - genetic: - Area - Reaction rate - Number of individuals - Frequency of genes, genotypes and - Density of phenotypes - Dynamics - Intrapopulation - Age composition polymorphism - Sex composition - Genetic unity 8

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Features of a population: 1. Individuals of one population are characterized by maximum similarity of characteristics due to the high possibility of crossing within the population and the same selection pressure. 2. Populations are genetically diverse Due to continuously emerging hereditary variability 3. Populations of the same species differ from each other in the frequency of occurrence of certain traits Under different conditions of existence, different traits are subject to natural selection 4. Each population is characterized by its own specific set of genes - the gene pool 10

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5. There is a struggle for existence in populations. 6. Natural selection operates, thanks to which only individuals with changes that are useful in the given conditions survive and leave offspring. 7. In areas of the range where different populations of the same species border, an exchange of genes occurs between them, ensuring the genetic unity of the species 8. The relationship between populations contributes to greater variability of the species and its better adaptability to living conditions 9. Due to relative genetic isolation, each population evolves independently of the others populations of the same species Being an elementary unit of evolution 11

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Population types

Geographical Ecological Local Elementary Forest in the Moscow region Crossbills live - Rodents in the Rodent family and in the Urals in spruce slopes and the bottom and pine ravine forest 12

Slide 13

Answer the following questions:

Can an individual be the unit of evolution? 2. Can a species be the unit of evolution? Why is a population considered the unit of evolution? Explain. Answer the test questions: 13

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Populations of different species differ

Sizes Numbers Age Forms of individuals and sexual composition of existence 14

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Patterns of inheritance of traits

Autogamous populations Allogamous populations Individuals of these populations Individuals of these populations are characterized by self-fertilization and cross-pollination Studied by a Danish botanist In 1908, V. Johansen J. Hardy and V. Weinberg established a pattern called the Hardy-Weinberg law 15

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Hardy-Weinberg Law

In an ideal population, allele and genotype frequencies are constant. Provided: - the number of individuals in the population is large enough;

- mating (panmixia) occurs randomly;

- there is no mutation process;

- there is no exchange of genes (gene drift, gene flow, waves of life) with other populations;

- there is no natural selection (i.e. individuals with different genotypes are equally fertile and viable). 16

Slide 17

Algorithm for applying Hardy Weinberg's Law

Let us assume that in a population individuals with genotypes AA and aa interbreed freely.

F1 genotype of the offspring - Aa F2 splitting will occur -1AA: 2Aa:1aa Let us denote: the frequency of the dominant allele - p the frequency of the recessive allele - g2 Then the frequency of these alleles in F1 will be: P Aa. Aa 17

Slide 18

Designation

Goal: to find out the frequency of all possible genotypes formed by different combinations of these allelic genes. Equipment: bags of balls (60 white and 40 red), three vessels. Work progress: 1. Red balls model the dominant gene A, white balls model the recessive gene A. 2. Pull 2 ​​balls out of the bag at a time. 3. Write down what combinations of balls by color are observed. 4. Count the number of each combination: how many times were two red balls drawn? How many times are red and white balls? How many times were two whites pulled out? Write down the numbers you get. 5. Summarize your data: what is the probability of drawing both red balls? Both white? White and red? 6. Based on the numbers you obtained, determine the frequency of genotypes AA, Aa and aa in this model population. 7. Do your data fit into the Hardy-Weinberg formula P2(AA) + 2 pq(Aa) + q2(aa) =1? 8. Summarize the findings for the whole class. Are they consistent with the Hardy-Weinberg law? Draw a conclusion based on the results of your work. 20

Slide 21

Let's think!

1.Formulate the law on the state of population equilibrium. 2.Under what conditions is the Hardy-Weinberg law observed? 3. Why can the manifestation of the Hardy-Weinberg law be detected only with an infinitely large population size? 21

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differential staining of chromosomes. Allows you to identify individual age and sex characteristics of chromosomes. There are chromosome variants that increase the viability of individuals. But there are also those that reduce viability: infertility, the birth of children with chromosomal pathology (1% are born, more than 100% have a clear clinical picture - syndrome. Antigenic biochemical polymorphism. Causes the diversity of people in proteins-enzymes and antigens. This leads to that each person may have his own characteristics of response to chemical, physical and biological environmental factors. On the basis of this, new directions in genetics have been formed: ecogenetics (a variant of individual responses to environmental conditions);

Clinical polymorphism. It manifests itself in the fact that there are many transitional forms from health to disease and many different options within one disease. All this leads to exceptional heterogeneity of hereditary diseases, and in order for a doctor to correctly make a diagnosis, one must be able to draw up a pedigree, study the phenotype when accepting a client, and be sure to put on “genetic glasses” in order to correctly draw up a pedigree.

Tit populations. Factors determining population dynamics. Biotic (reproductive) potential. Ptarmigan Survival Chart. Types of population dynamics. Change in population size. Mortality. Factors determining fluctuations. Monovoltage types. Theory of population interaction. Logistic model of population growth. Survival tables. Equation for exponential population growth.

“Types of population dynamics” - Indicator. Scheme. Survival charts. Professor G. A. Viktorov. Mass spawning. Share of animals. Two typical options. Fertility and survival tables. Regulation. The magnitude of biotic potential. Intensity. Long-term dynamic cycles. Decrease in mortality. Population dynamics. Mass development of false caterpillars. Population dynamics. Dynamics of populations of animal organisms. Environmental factors.

“Study of population” - Fertility - the ability to increase numbers. Population structure. The concept of demecology. The concept of population. WWF. Population is an elementary grouping of individuals of the same species. Survival curves. Group effect. Intraspecific relationships in a population. Interspecific relationships in a population. Spatial divisions of the population. Sexual structure – the ratio of individuals by sex. Elementary (micropopulation).

“Population indicators” - Population waves. A collection of individuals of the same species. Logistics growth. Specific birth rate. Exponential growth. Populations. Survival curves. The rate of change in population size. Quantitative population indicators. Structure indicators. Dynamics of population growth. Static indicators. Survival. Dynamic indicators. Impact of environmental factors. Survival.

“Population genetics” - Genetic processes. Genetic population. The solution of the problem. Calculation of genotype frequencies. Mutation pressure. Let's make a proportion. Genotype. Pattern. Hardy-Weinberg law. Panmixia conditions. Calculation of allele frequency. Actual series. Theoretical frequencies. Solving typical problems. Impact of mutations. Calculation of allele frequency in heterozygotes. Gene. Change over a generation. Aa heterozygotes. The population is declining.

"Population Characteristics" - Subspecies. Pattern. Populations of different species. Population or species. Law on the state of population equilibrium. Algorithm for applying the law. Calculate the frequency of occurrence of any dominant and recessive gene in a population. Population. A separate individual. Population definitions. Frequency of the dominant allele. Struggle for existence. Let's think about it. Types of populations. Allele frequencies. Term. Population characteristics.