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Presentation on the topic of population genetics. Biology presentation "population genetics"

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let's think 2

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Problem question:

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

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Species Subspecies

Populations Flock Herd Pride (herd) (family) 4

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The term population was introduced in 1903 by W. 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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Analyze the following population definitions:

A set of individuals of the same species occupying a separate territory within the range of the species, freely interbreeding with each other to some extent isolated from other populations of this species. Any self-reproducing collection of individuals of the same species, more or less isolated in space and time from other similar populations of the same species. A group of individuals of the same species that share a common gene pool and occupy a specific area. A set of individuals of the same species, inhabiting a certain space for a long time, and within which, to a certain extent, panmixia (crossing) is carried out and separated from other sets by one degree or another of isolation. 6

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Use the available material to formulate the concept - population

Population (from lat. Porulos - 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 the population: 1. Individuals of the same population are characterized by the maximum similarity of traits Due to the high possibility of interbreeding within the population and the same selection pressure. 2. Populations are genetically diverse Due to the 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 Due to which only individuals with changes that are useful in given conditions survive and leave offspring. 7. In areas of the range where different populations of the same species border, there is an exchange of genes between them, which ensures the genetic unity of the species 8. The relationship between populations contributes to the greater variability of the species and its better adaptation 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

Geographic Ecological Local Elementary Forest in the Moscow region Crossbills inhabited - Rodents on the Family of rodents and on the Urals in the spruce slopes and bottom and pine ravine forest 12

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Answer the questions posed:

Can an individual be a unit of evolution? 2. Can a species be a 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 are different

Sizes Numbers Age Forms of individuals and sexual joint 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, separate breeding and cross-pollination Studied by a Danish botanist In 1908 V. Johansen J. Hardy and W. Weinberg established a regularity 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, life waves) with other populations; - there is no natural selection (i.e. individuals with different genotypes are equally fertile and viable). 16

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Algorithm for applying Hardy Weinberg's Law

Let us assume that individuals with the AA and aa genotypes freely interbreed in the population. F1 offspring genotype - Aa F2 splitting will occur -1AA: 2Aa: 1aa 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

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Designation

Р - dominant allele frequency g - recessive allele frequency p2 - homozygous dominant genotype 2pq - heterozygous genotype q2 - homozygous recessive genotype. The sum of the occurrence of all three genotypes - AA, Aa, aa \u003d 1, then the frequency of occurrence of each genotype will be as follows: 1AA: 2Aa: aa 0.25: 0.50: 0.25 18

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

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

Purpose: to find out the frequency of all possible genotypes formed by various combinations of these allelic genes. Equipment: bags with balls (60 white and 40 red), three vessels. Progress of work: 1. Red balls model the dominant gene A, white - the recessive gene a. 2. Pull out 2 balls from the bag at the same time. 3. Write down what combinations of balls by color are observed. 4. Count the number of each combination: how many times have two red balls been drawn? How many times - red and white balls? How many times have two whites been drawn? 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 received, determine the frequency of the genotypes AA, Aa and aa in this model population. 7. Do your data fit the Hardy-Weinberg formula P2(AA) + 2 pq(Aa) + q2(aa) =1? 8. Summarize the data of the whole class. Do they agree with the Hardy-Weinberg law? Make a conclusion based on the results of your work. twenty

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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? 21

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Population - a collection of individuals of a given species, for a long time (several generations) inhabiting a certain space, 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, provided that real possibility crossing any male with any female, combining any gametes (gene alleles) of one sex with any gametes (gene alleles) of the other sex within its 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. No mutation process

A genetic population is a model that allows you to trace the genetic processes that take place in any real-life population: 1. Determine the actual genetic structure of the population 2. Determine the level of prevalence of hereditary diseases in the population 3. Study what patterns the frequency of occurrence of various genotypes obeys 4. Determine the evolutionary paths of populations

Properties of a genetic population: Plasticity of the genetic structure, which changes 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 environmental conditions change Preservation of the overall genetic structure corresponding to environmental conditions and the manifestation of genetic homeostasis due to the presence of adaptive abilities of this structure The ability to unlimited evolution

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

Calculation of allele frequency in heterozygotes (example 2) If the population consists of 30 heterozygous individuals (Aa), then there are only 60 alleles (A + a) in the population, including 30 - "A" and 30 - "a". The frequency of the dominant allele is indicated by the sign p, and the frequency of the recessive - 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 the frequency of alleles in a heterogeneous population (example 3) It is required to determine the frequency of 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 AA owns have 64% of A alleles, 32% of Aa have 16% of “A” alleles and 16% of “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 \u003d 1, then under the condition of panmixia, an equilibrium of genotypes is established in the first generation, which is preserved in all subsequent generations; equilibrium is expressed by the formula: p 2 AA + 2pqAa + q 2 aa = 1

Solution of the problem 1 p 2 AA + 2pqAa + q 2 aa = 1 By condition q 2 aa = 16% = 0.16 Hence qa = 0.4 Hence pA = 1 - qa = 1 - 0.4 = 0.6 population is as follows: 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 occurred due to recessive genes. Therefore, the ratio between pA and qa has changed towards an increase in 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 next generation population, the new values of p and q (pA = 0.7, qa = 0.3) are substituted into the Hardy-Weinberg law formula: 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 \u003d 1 0, × 0.825 × 0.175 2 \u003d 1 0.68 + 0.29 + 0.03 or \u003d 100

Actual series: =100 Theoretical series: =100 Based on the comparison of the actual and theoretical series of numbers, the conclusion suggests itself 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 agreement criterion makes it possible to compare the actual series of numbers with the theoretical ones and answer the question of their correspondence (or discrepancy) to each other Where 0 - actual frequencies E - theoretical frequencies If χ 2 = 0, then there is a complete correspondence of the actual splitting to the theoretically expected. At χ 2 actual > χ 2 theoretical differences are significant χ 2 theoretical differences are significant ">

χ 2 \u003d (65-68) 2 / 68 \u003d 36/29 + 9 / \u003d 4.37 χ 2 tab. = 5.99 Therefore, the conclusion is not reliable, there is a balance.

Influence of mutations Let pA = 1, qa = 0 Gene “A” mutates into “a” with frequency = 0.00003 Back mutations with frequency 0.00001 population per generation will be

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

It can be seen from the example that with different probabilities of direct and reverse mutations of any gene in the population, the frequency of that allele of this gene will increase, in the direction of which mutations occur with a greater probability. 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 emerging direct mutations becomes equal to the number of back mutations, i.e. when wq = up

Tit populations. Factors determining the population dynamics. Biotic (reproductive) potential. Partridge survival chart. Types of population dynamics. Population change. Mortality. Factors determining fluctuations. Monovoltine types. Theory of interaction of populations. Logistic model of population growth. survival tables. Equation of 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 value of the biotic potential. Intensity. Long-term cycles of dynamics. Decrease in mortality. Population dynamics. Mass development of caterpillars. Population dynamics. Population dynamics of animal organisms. Factors external environment.

"Studying the population" - Fertility - the ability to increase the number. Population structure. The concept of deecology. The concept of a population. WWF. A 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. Rate of population change. Quantitative indicators of the population. Structure indicators. Population growth dynamics. static indicators. Survival. Dynamic indicators. Impact environmental factors. Survival.

"Population genetics" - Genetic processes. genetic population. The solution of the problem. Calculation of frequencies of occurrence of genotypes. mutational pressure. We make a proportion. Genotype. Pattern. Hardy-Weinberg law. Panmixia conditions. Allele frequency calculation. actual row. Theoretical frequencies. Solution of typical tasks. Influence of mutations. Calculation of allele frequency in heterozygotes. Gene. Change over a generation. Aa heterozygotes. The population is declining.

"Characteristics of the population" - Subspecies. Pattern. Populations different types. population or species. Law on the state of population equilibrium. Algorithm for applying the law. Calculate the frequency of occurrence in the population of any dominant and recessive gene. population. Separate entity. Population definitions. Dominant allele frequency. Struggle for existence. Let's think. Population types. allele frequencies. Term. population characteristics.

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Lesson on the topic: Population. Genetic composition of populations

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

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Let's think

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Is a population or species an elementary unit of evolution?

Problem question:

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Populations Flock Herd Pride (herd) (family)

Species Subspecies

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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 W. Johansen

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Analyze the following population definitions:

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Population (from lat. Porulos - people, population) -

Use the available material to formulate the concept - population

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Population characteristics

Relationships of organisms in populations

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Features of the population: 1. Individuals of the same population are characterized by the maximum similarity of traits Due to the high possibility of interbreeding 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

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Geographic Ecological Local Elementary Forest in the Moscow region Crossbills inhabited - Rodents on the Family of rodents and on the Urals in the spruce slopes and bottom and pine ravine forest

Population types

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

Answer the questions posed:

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

Populations of different species are different

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Autogamous populations Allogamous populations Individuals of these populations Individuals of these populations are characterized by self-fertility, separate breeding 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

Patterns of inheritance of traits

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Hardy-Weinberg law

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Algorithm for applying Hardy Weinberg's Law

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Designation

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

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Purpose: to find out the frequency of all possible genotypes formed by various combinations of these allelic genes. Equipment: bags with balls (60 white and 40 red), three vessels. Progress of work: 1. Red balls model the dominant gene A, white - the recessive gene a. 2. Pull out 2 balls from the bag at the same time. 3. Write down what combinations of balls by color are observed. 4. Count the number of each combination: how many times have two red balls been drawn? How many times - red and white balls? How many times have two whites been drawn? 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 received, determine the frequency of the genotypes AA, Aa and aa in this model population. 7. Do your data fit the Hardy-Weinberg formula P2(AA) + 2 pq(Aa) + q2(aa) =1? 8. Summarize the data of the entire class. Do they agree with the Hardy-Weinberg law? Make a conclusion based on the results of your work.

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

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Let's think!

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

Genetic balance in populations.

The 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.
With relatively constant conditions and
high population 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 equilibrium is established, or
the constancy of the 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
undirected, random. More often
they are all related to fluctuations
the number of natural populations or with
spatial isolation of the part
organisms in this population.

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

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

Similar changes can be observed when 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 that lived there into two parts.
The gene pool of a small population originating from a small
the number of individuals, maybe, again due to random
reasons, differ from the original gene pool in composition.
It will carry only those genotypes that
randomly selected among a small number of founders
new population.
Rare alleles may be common in a new
population that arose as a result of its isolation from
original population.

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

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

Periodic fluctuations in population are characteristic of almost all organisms.

Sharp fluctuations in populations
whatever they are caused, they change
allele frequency in the gene pool of populations.
When creating unfavorable conditions and
population decline due to
death of individuals may occur loss
some genes, especially rare ones.
In general, the smaller the number
population, the higher the probability of loss
rare genes, the greater the impact
have on the composition of the gene pool random
factors.

Gene 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
drift of genes.
Genetic drift can result in
viable population with a peculiar
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 be extended 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 the data
conditions) and to reduce others.
Due to natural selection in the gene pool
populations, useful genes are fixed, i.e.
favorable for the survival of individuals in the data
environmental conditions. Their share is increasing, and the total composition
the gene pool is changing.
Changes in the gene pool under the influence of natural
selection leads to changes in phenotypes,
features of the external structure of organisms, their
behavior and lifestyle, and ultimately to
better fit of the population to the data
environmental conditions.

Questions

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

Presentation on the topic of population genetics. Biology presentation "population genetics"

Problem question:

Species Subspecies

The term population was introduced in 1903 by W. Johansen

Analyze the following population definitions:

Use the available material to formulate the concept - population

Population characteristics

Population types

Answer the questions posed:

Populations of different species are different

Patterns of inheritance of traits

Hardy-Weinberg law

Algorithm for applying Hardy Weinberg's Law

Designation

Let's think!

Genetic balance in populations.

Causes of genetic imbalance.

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

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

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

Periodic fluctuations in population are characteristic of almost all organisms.

Gene drift

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

Questions

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