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Presentation “Population genetics. Changes in the gene pool of populations Presentation of the population and their genetic composition

What is the gene pool of a population?
Possessing a specific gene pool,
under control
natural selection,
populations play vital role V
evolutionary transformations of the species.
All processes leading to change
species, begin at the species level
populations.

Genetic balance in populations.

Frequency of occurrence of various alleles in
population is determined by the frequency of mutations,
selection pressure and sometimes exchange
hereditary information with others
populations as a result of migrations of individuals.
Under conditions of relative constancy and
high population size all of the above
processes lead to a state of relative
balance. As a result, the gene pool of such
populations becomes balanced, in it
genetic balance is established, or
constancy of frequencies of occurrence of various
alleles.

Causes of genetic imbalance.

the action of natural selection leads to
directed changes in the gene pool
population - increasing the frequencies of “useful”
genes. Microevolutionary
changes.
However, changes in the gene pool can also be
undirected, random. More often
all of them are associated with fluctuations
the number of natural populations or with
spatial isolation of the part
organisms of this population.

Undirected, random changes in the gene pool can occur due to various reasons - migration, i.e. movement of part

populations into the new
habitat.
If a small part of the animal population or
plants settle in a new place, gene pool
the newly formed population will inevitably
less gene pool of the parent population. IN
due to random reasons of allele frequency in a new
populations may not coincide with those of
original. Genes that were previously rare
can spread quickly (due to
sexual reproduction) among individuals of the new
populations. And previously widespread
genes may be absent if they were not in
genotypes of the founders of the new settlement.

Similar changes can be observed in cases where a population is divided into two unequal parts by natural or

artificial barriers.
For example, a dam was built on a river, dividing
the fish population living there into two parts.
The gene pool of a small population originating from a small
number of individuals, maybe, again due to random
reasons, differ from the original gene pool in composition.
He will carry only those genotypes that
randomly selected among a small number of founders
new population.
Rare alleles may turn out to be common in a new
population that arose as a result of its isolation from
source population.

The composition of the gene pool can change due to various natural disasters, when only a few organisms remain survivors

(for example due to
floods, droughts or fires).
In a population that survived a disaster, consisting of
individuals surviving by chance, composition
the gene pool will be formed from randomly
selected genotypes.
Following the decline in numbers, a massive
reproduction, which begins
small group.
The genetic composition of this group will determine
genetic structure of the entire population during its period
heyday However, some mutations can completely
disappear, and the concentration of others - sharply
will rise. The set of genes remaining in living individuals
may differ slightly from the one
existed in the population before the disaster.

Periodic fluctuations in numbers are characteristic of almost all organisms

Sharp fluctuations in population numbers,
whatever causes them, they change
frequency of alleles in the gene pool of populations.
When creating unfavorable conditions and
population decline due to
loss of individuals may occur
some genes, especially rare ones.
In general, the smaller the number
population, the higher the probability of loss
rare genes, the greater the influence
random influences on the composition of the gene pool
factors.

Genetic drift

The action of random factors combines and
changes the gene pool of a small population compared to
its original state. This phenomenon is called
genetic drift.
As a result of genetic drift, there may be
viable population with a distinctive
gene pool, largely random, since selection
in this case did not play a leading role.
As the number of individuals increases again
the action of natural selection will be restored,
which will apply to the new
gene pool, leading to its directed changes.
The combination of all these processes can lead to
isolation of a new species.

Directed changes in the gene pool occur as a result of natural selection.

Natural selection leads to consistent
an increase in the frequencies of some genes (useful in data
conditions) and to a decrease in others.
Due to natural selection in the gene pool
useful genes are fixed in populations, i.e.
favoring the survival of individuals in the data
environmental conditions. Their share is increasing, and the overall composition
the gene pool is changing.
Changes in the gene pool under the influence of natural
selection lead to changes in phenotypes,
features external structure organisms, their
behavior and lifestyle, and ultimately to
better fit of the population to the data
conditions external environment.

Questions

1. Under what conditions is it possible?
balance between different
alleles of the population gene pool?
2. What forces caused
directed changes in the gene pool?
3. What factors are
cause of genetic disorder
equilibrium

Slide 2

Let's think 2

Slide 3

Problematic question:

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

Slide 4

SpeciesSubspecies

Populations Pack Herd Pride (herd) (family) 4

Slide 5

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

Slide 6

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

Slide 7

Use the available material to formulate the concept - population

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

Slide 8

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

Slide 10

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 they are subject to natural selection different signs 4. Each population is characterized by its own specific set of genes - gene pool 10

Slide 11

5. There is a struggle for existence in populations. 6. Works natural selection 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

Slide 12

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

Slide 14

Populations of different species differ

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

Slide 15

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

Slide 16

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

P - frequency of the dominant allele g - frequency of the recessive allele p2 - homozygous dominant genotype 2pq - heterozygous genotype q2 - homozygous recessive genotype. The sum of the occurrence of all three genotypes is AA, Aa, aa = 1, then the frequency of occurrence of each genotype will be as follows: 1AA: 2Aa: aa 0.25: 0.50: 0.25 18

Slide 19

Using the Hardy-Weinberg law, you can calculate the frequency of occurrence in a population of any dominant and recessive gene, as well as various genotypes, using the formulas:

Slide 20

Practical work: “Modeling the Hardy-Weinberg law (work is done in groups)

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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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 inconsistency) with each other. Where 0 – actual frequencies E – theoretical frequencies If χ 2 = 0, then observed full compliance actual splitting to what is theoretically expected. 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 say 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

Description of the presentation by individual slides:

1 slide

Slide description:

Topic: “Genetics of Populations” Objectives: To study the genetic basis of the structure and evolution of populations. Learn to solve problems related to the gene pool of populations.

2 slide

Slide description:

A population is a collection of individuals of the same species, living for a long time in a certain territory, freely interbreeding with each other, having a common origin, a certain genetic structure and, to one degree or another, isolated from other such collections of individuals of a given species. A population is not only a unit of a species, a form of its existence, but also a unit of evolution. Population characteristics

3 slide

Slide description:

Elementary evolutionary material – mutations (?). The elementary evolutionary unit is a population. (According to Lamarck? According to Darwin?) Microevolutionary processes that culminate in speciation are based on genetic transformations in populations. He studies the genetic structure and dynamics of populations special section genetics - population genetics. Population characteristics

4 slide

Slide description:

From a genetic point of view, a population is an open system, while a species is a closed one. In general form, the process of speciation comes down to genetic transformation open system into a genetically closed one. Each population has a specific gene pool and genetic structure. The gene pool of a population is the totality of the genotypes of all individuals in the population. The genetic structure of a population is understood as the ratio of different genotypes and alleles in it. Population characteristics

5 slide

Slide description:

One of the basic concepts of population genetics is genotype frequency and allele frequency. The frequency of a genotype (or allele) is understood as its proportion related to total number genotypes (or alleles) in a population. The frequency of a genotype, or allele, is expressed either as a percentage or as a fraction of a unit. So, if a gene has two allelic forms and the share of the recessive allele a is ¾ (or 75%), then the share of the dominant allele A will be equal to ¼ (or 25%) of the total number of alleles of this gene in the population. Population characteristics

6 slide

Slide description:

Population characteristics Populations of self-pollinating and cross-pollinating plants differ significantly from each other. The first study of the genetic structure of a population was undertaken by V. Johannsen in 1903. Populations of self-pollinating plants were selected as objects of study. Having studied the seed mass of beans for several generations, he discovered that in self-pollinators the population consists of genotypically heterogeneous groups, the so-called pure lines, represented by homozygous individuals.

7 slide

Slide description:

Characteristics of the population Moreover, from generation to generation in such a population an equal ratio of homozygous dominant and homozygous recessive genotypes is maintained. Their frequency increases in each generation, while the frequency of heterozygous genotypes will decrease. Thus, in populations of self-pollinating plants, a process of homozygotization, or decomposition into lines with different genotypes, is observed.

8 slide

Slide description:

Hardy-Weinberg Law Most plants and animals in populations reproduce sexually through free mating, which ensures that gametes are equally likely to occur. The equal occurrence of gametes during free crossing is called panmixia, and such a population is called panmictic. In 1908, the English mathematician G. Hardy and the German physician N. Weinberg independently formulated a law governing the distribution of homozygotes and heterozygotes in a panmictic population, and expressed it in the form of an algebraic formula.

Slide 9

Slide description:

Hardy-Weinberg Law The frequency of occurrence of gametes with the dominant allele A is denoted by p, and the frequency of occurrence of gametes with the recessive allele a is denoted by q. The frequencies of these alleles in a population are expressed by the formula p + q = 1 (or 100%). Since gametes are equally likely to occur in a panmictic population, genotype frequencies can also be determined. Hardy and Weinberg, summing up data on the frequency of genotypes formed as a result of equally probable occurrence of gametes, derived a formula for the frequency of genotypes in a panmictic population: AA + 2Aa + aa = 1 P2 + 2pq + q2 = 1

10 slide

Slide description:

Hardy-Weinberg Law Using these formulas, it is possible to calculate the frequencies of alleles and genotypes in a specific panmictic population. However, this law is subject to the following conditions: Unlimitedly large population size, ensuring free crossing of individuals with each other; All genotypes are equally viable, fertile and are not subject to selection; Forward and reverse mutations occur with equal frequency or are so rare that they can be neglected; There is no outflow or influx of new genotypes into the population.

11 slide

Slide description:

Hardy-Weinberg Law In real existing populations, these conditions cannot be met, so the law is valid only for an ideal population. Despite this, the Hardy-Weinberg law is the basis for the analysis of some genetic phenomena occurring in natural populations. For example, if it is known that phenylketonuria occurs with a frequency of 1:10,000 and is inherited in an autosomal recessive manner, you can calculate the frequency of heterozygotes and homozygotes for a dominant trait.

12 slide

Slide description:

Hardy-Weinberg law Patients with phenylketonuria have a genotype q2(aa) = 0.0001. Hence q = 0.01. p = 1 - 0.01 = 0.99. The frequency of occurrence of heterozygotes is 2pq, equal to 2 x 0.99 x 0.01 ≈ 0.02 or ≈ 2%. Frequency of occurrence of homozygotes for dominant and recessive traits: AA = p2 = 0.992 = 0.9801 ≈ 98%, aa = q2 = 0.012 = 0.0001 = 0.01%.

Slide 13

Slide description:

Hardy-Weinberg Law Factors changing the genetic structure of a population: Changing the balance of genotypes and alleles in a panmictic population occurs under the influence of constantly operating factors, which include: 1. Mutation process; 2. Population waves; 3. Insulation; 4. Natural selection; 5. Genetic drift and others. It is thanks to these phenomena that an elementary evolutionary phenomenon arises - a change in the genetic composition of the population, which is the initial stage of the process of speciation.

Slide 14

Slide description:

Hardy-Weinberg Law Problem: A gene in a population has two allelic forms and the proportion of the recessive allele a is ¾ (or 75%). What is the frequency of occurrence of each genotype in this population?

15 slide

Slide description:

Population: A population is a collection of individuals of the same species, living for a long time in a certain territory, freely interbreeding with each other, having a common origin, a certain genetic structure and, to one degree or another, isolated from other such collections of individuals of a given species. Gene pool of a population: The gene pool of a population is the totality of genotypes of all individuals in the population. Elementary evolutionary material: Mutations. Elementary evolutionary unit: Population. Elementary evolutionary phenomenon: Change in the gene pool of a population. Genetic structure of a population: The genetic structure of a population is understood as the ratio of different genotypes and alleles in it. Ideal population: A population in which 4 conditions are met: An unlimitedly large population size, ensuring free crossing of individuals with each other; There are no mutations, or direct and reverse mutations occur with equal frequency or are so rare that they can be neglected; There is no migration, or there is no outflow or influx of new genotypes into the population. No selection; Let's summarize:

16 slide

Slide description:

Why is a population an open structure, and a species a closed one? Crossing between individuals of different populations is possible, but between individuals of different species is not. Why doesn't the Hardy-Weinberg law apply to peas? Peas are self-pollinators. In populations of self-pollinating plants, a process of homozygotization, or decomposition into lines with different genotypes, is observed. Which population is called panmictic? A population in which gametes are equally likely to occur during free crossing (panmixia). Let's summarize:

Slide 17

Slide description:

Hardy-Weinberg Law Problem: On Umnak Island in 1824, silver foxes were killed - 40 (BB), gray foxes - 95 (Bb), red foxes 51 (bb). Determine genotype frequencies, allele frequencies, compare observed relationships with theoretical ones. Let us divide the number of individuals with each genotype by total number and we get the following genotype frequencies: BB: 40/186 = 0.215; Bb: 95/186 = 0.511; bb: 51/186 = 0.274. Let's determine allele frequencies. Since each individual had two alleles (the same or different), the total number of alleles is equal to twice the number of individuals in the sample: p(B) = (2BB + Bb)/2(BB + Bb + bb) = (2 x 40 + 95) /2(40 + 95 + 51) = 0.470. g = 1 - p = 0.530. The expected genotype ratio should be: BB = 0.4702 = 0.221; Bb = 2 x 0.470 x 0.530 = 0.498 and bb = 0.5302 = 0.281. If we multiply these values by the number of individuals in the sample, we find that at equilibrium there should be 0.221 x 186 = 41 black foxes, 0.498 x 186 = 93 gray foxes, and 0.281 x 186 = 52 red foxes in the population.

18 slide

Slide description:

Hardy-Weinberg Law Problem: On the Nushagak Peninsula in 1824, 1 silver fox (BB), 7 gray fox (Bb), and 121 red fox (bb) were killed. Determine genotype frequencies, allele frequencies, compare observed relationships with theoretical ones. Let us divide the number of individuals with each genotype by the total number (129) and obtain the following genotype frequencies: BB: 1/129 = 0.0078; Bb: 7/129 = 0.054; bb: 121/129 = 0.938. Let's determine allele frequencies. Since each individual had two alleles (the same or different), the total number of alleles is equal to twice the number of individuals in the sample: p(B) = (2BB + Bb)/2(BB + Bb + bb) = (2 x 1 + 7) /2(1 + 7 + 121) = 0.0349. g = 1- p = 0.9651. The expected genotype ratio should be: BB = 0.03492 = 0.0012; Bb = 2 x 0.0349 x 0.9651 = 0.0674 and bb = 0.96512 = 0.9314. If we multiply these values by the number of individuals in the sample, we find that at equilibrium there should be 0.0012 x 129 = 0.15 blacks in the population; 0.0674 x 129 = 9 gray foxes and 0.9314 x 129 = 120 red foxes.

Slide 19

Slide description:

Hardy-Weinberg Law Problem: On Umnak Island in 1824 there lived 40 silver foxes (BB), 95 gray foxes (Bb), 51 red foxes (bb). Let's assume that the red foxes died as a result of the epidemic. Determine the genotype frequencies and allele frequencies in the remaining foxes in this and the next generation of foxes. Let us divide the number of individuals with each genotype by the total number and obtain the following genotype frequencies: BB: 40/135 = 0.2963; Bb: 95/135 = 0.7037. Let's determine allele frequencies. Since each individual had two alleles (the same or different), the total number of alleles is equal to twice the number of individuals in the sample: p(B) = (2BB + Bb)/2(BB + Bb) = (2 x 40 + 95)/2 (40 + 95) = 0.648. g = 1 - p = 0.352. In the next generation, the genotype ratio should be: BB = 0.6482 = 0.42; Bb = 2 x 0.648 x 0.352 = 0.456; bb = 0.3522 = 0.124. A new equilibrium state of the population will be established.

Slide 1

Lesson on the topic: Population. Genetic composition of populations

Goal: Expand and deepen knowledge about the population as an obligatory and structural unit of the species. Prepared by Urmanova A.Kh.

Slide 2

Let's think

Slide 3

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

Problematic question:

Slide 4

Populations Pack Herd Pride (herd) (family)

Species Subspecies

Slide 5

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

The term population was introduced in 1903 by V. Johansen

Slide 6

Review the following population definitions:

Slide 7

Population (from Latin Poрulos – people, population) -

Use the available material to formulate the concept - population

Slide 8

Population characteristics

Relationships between organisms in populations

Slide 10

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

Slide 11

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

Slide 12

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

Population types

Slide 13

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:

Answer the following questions:

Slide 14

Size Number Age Forms of individuals and sexual composition of existence

Populations of different species differ

Slide 15

Patterns of inheritance of traits

Slide 16

Hardy-Weinberg Law

Slide 17

Algorithm for applying Hardy Weinberg's Law

Slide 18

Designation

Slide 19

Using the Hardy-Weinberg law, you can calculate the frequency of occurrence in a population of any dominant and recessive gene, as well as various genotypes, using the formulas:

Slide 20

Practical work: “Modeling the Hardy-Weinberg law (work is done in groups)

Slide 21

Let's think!