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This presentation has been supported by the Erasmus

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Plus K2 Cooperation Partnerships.

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Innovation of the structure and content of study programs
in the field of animal

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genetic and food resources 

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management with

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the use of 

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digitalization.

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The European Commission support
for the production of this presentation

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does not constitute and endorsement of the contents,
which reflects the views only of the authors.

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And the Commission cannot be held responsible for any use
which may be made of the information contained therein.

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The name of the speaker is Katarzyna Andraszek,
and she works for the Institute of Animal Science and Fisheries

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Faculty of Agrobioengineering and Animal Husbandry

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in Siedlce this University of Natural Sciences and Humanities.

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She would like to present a presentation on Heterosis, inbreeding depression.

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Heterosis means hybrid vigour 
increased viability 

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and vigour of animals and plants derived by crossbreeding genetically different forms.

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Heterosis is the opposite of inbreeding depression,
 
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and is manifested as an increase in fertility, body size, growth rate

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and other traits caused by higher heterozygosity in F1 

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individuals obtained by crossing two different homozygous lines.

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The phenomenon of heterosis is widely exploited in plant and animal breeding.

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To obtain heterozygous individuals 

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and the effect of heterosis

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it is necessary to mate individuals

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from lines that are as homozygous as possible and therefore at high risk of inbreeding depression. 

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The effect of heterosis is best seen when inbreeding depression

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previously occurs but is not so severe

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that it greatly reduces the viability 

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or fertility of animals.

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Individuals of the F1 generation 

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will have values of traits (including productivity) 

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at a level represented by 

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the pure parent line with the higher value for the trait. 

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The effect of heterosis will occur 

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only in the first generation obtained 

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by crossing the parent lines. 

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The successive F2, F3, .... Fn generations 

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will have normal parameters 

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of traits and will not exhibit the hybrid vigour effect.

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The genetic background of heterosis 

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is explained by two hypotheses.

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The overdominance hypothesis assumes 

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that the combination

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of two opposing alleles at a given locus in the heterozygote has a greater,

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more beneficial effect than the two identical alleles

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in the homozygote; for example, heterozygous individuals (Aa) 

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are resistant to more parasites than homozygous individuals (AA or aa),

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In heterozygous individuals, 

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both allelic forms (dominant and recessive) 

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of the gene are expressed,

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so that the effects of their expression overlap, 

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ultimately resulting in a higher value for the trait.

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On the graph here we can see the effect of enhanced gene expression

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in individuals of the F1 generation. 

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The size 

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of the oval illustrates the value

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of the trait in individuals of a given group 

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The dominance

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hypothesis assumes 

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that the deleterious effect of recessive alleles

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is manifested to a lesser extent in heterozygous individuals

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than in recessive homozygotes

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On the graph 

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here we can see  

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the deleterious effect 

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of the recessive allele. 

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The size of the oval 

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illustrates 

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the value 

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of the trait 

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in individuals of a 

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given group.

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The two hypotheses

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have different consequences 

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in gene expression. 

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The main cause
 
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of heterozygous is overdominance

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then certain genes should be overexpressed
in the offspring relative to the parents

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due to the overlapping of the effects of the two alleles.

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In contrast,

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if it is the other hypothesis
that explains the better condition of crossbred,

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then fewer genes with low expression should be manifested

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in the offspring in comparison with the parents.

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In addition

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virtually the expression 

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should be comparable

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to that observed

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in the superior parent.

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The heterosis effect is often exploited in plant breeding.

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Special parent lines are often bred in order

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to obtain hybrids that will be more productive.

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An example of exploitation of heterosis,

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which is very widespread in plant
breeding is maize grain for grain.

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The now you have enough.

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Now I would like to present some examples of the effects

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of heterosis in animal breeding

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AIn cattle, Aberdeen Angus x Hereford crossbreds, 

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known as „Black Baldy”, which are very popular in North America, 

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Australia and New Zealand have higher values for meat traits.

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In addition,

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this cross is used

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in heifers in order to obtain calves of smaller size

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and thus reduce the risk of complications during delivery,

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which are characteristic of Herefords „Black Baldy” cows

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also have very good maternal characteristics.

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In pigs, 

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an example is Hampshire x Yorkshire crossbreds

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known as „Blue Butts”

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In poultry, 

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the two breeds White Rocks 

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x White Cornish 

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are crossed to obtain commercial 

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broilers.

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The crossbreds inherit greater body size from the White Cornish breed, 

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and greater daily weight gains from White Rocks.

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Estimation of the effects of heterosis

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The effect of heterosis and its magnitude can be defined as:

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the percentage increase in the value of a trait relative to the parent population with the better value for the trait,

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the percentage increase in the value of 

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heterozygotes relative to the average for one parent population or the average value for both parent populations,

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the percentage increase in the value 

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of zero.

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The percentage

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increase in the value

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of a trait in the F1 generation relative to the best value observed

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in commercial cultivation in a given region used for plants.

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The effect 

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of heterosis can be estimated by comparing the values

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of the parent populations
and the populations resulting from cross-breeding.

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If the value of the traits in parent line a

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a is the following equation
where: µ – average value of the trait in the population; 

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aA – effect of direct genetic factors (breeding value)
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mA – maternal genetic effect
and the value of the trait in parent population B (µB)

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is expressed by the following equation

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where: µ - average value of the trait in the population;  

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aB – effect of direct genetic factors (breeding value);

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mB – paternal genetic effect.

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If hidden

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beneath, then the value of the traits in the F1 generation
obtained by mating line

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A Females with line B males will be expressed by the equation below.

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Laws should

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imagine Lego

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effort mapped in this plot as a pet,

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whereas the value obtained by mating of males from line B

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with females from linear
will be expressed by the following equation.

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Your virtuous circle populous of hidden

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little red Nevada outer circle popularity plus

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popularity olsavsky e map tonight

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where HB is the effect of heterozygous

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B expressed in the units used for a given trait f

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lg Montana ultra itself, but also

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based on these assumptions,

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the effect of hetero CIS can be estimated
according to the following formula.

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Unibet ora some unibet

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some time using the app minnows should

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hold of Lana,

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but Pulaski approaches

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to Sammy when usage of Vanya is in.

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Sometimes however,

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crossing of inbred parent lines does not result in head to races,

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and the crossbreed offspring has the same trait values

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as the parents or inferior values.

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The of

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this phenomenon is called out breeding depression.

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It affects wild animal populations more often

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than farmed animals
and is most likely linked to the fact that the parent populations

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are better adapted as a result of long term selection
for specific environmental conditions.

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Manifesting the best values of the traits

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to traits.

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Heterozygous offspring, on the other hand,

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leads these abilities through mixing of the effects of the animals.

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This may also be linked to insufficient genetic distance
between the parent populations,

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so that heterozygous does not appear in the offspring of a group.

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The initial kit that elzey or paternal

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colonial needs will ease the pressure in inbreeding.

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Depression is one of the main factors
reducing the adaptive capacity of inbred organisms

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and their viability in comparison
to non inbred individuals, significantly increasing the risk of

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or ultimately causing the extinction of a population,

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especially a small one.

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Policy Struggles

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Inbreeding depression

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may appear in a population
in which inbreeding takes place as a consequence

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of the increased homosexuality
resulting from this type of mating go up.

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It's nasty when you can say cohesion proclivities,

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rules that underlie my different

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ALS have effects of varying strength on the body, on traits

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determining adaptation to environmental conditions

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which are crucial for the functioning of the body and its survival.

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On this ecosystem,

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deleterious aliens are eliminated

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from the population by natural selection policy problem.

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Depressing the problem of inbreeding.

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Depression really affects large populations
because the effects of deleterious genes are seldom manifested.

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Especially when mating is random.

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However, it plays an important role

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in small populations in which there is a high probability

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of inbreeding and of two copies of the same deleterious illegal

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being passed on to the offspring in which its effect is manifested.

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Voyager one If the frequency of recessive

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homozygous in a population
in which random mating takes place is kitty,

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then in an inbred population, the frequency will be two

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plus tcf, whereas is the inbreeding coefficient.

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This has a significant impact on the incidence of diseases

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or deleterious traits in the population.

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I was not disputing sporting inbred.

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Matt doesn't have chance of birth.

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In the case of random mating,
if the frequency of a recessive animal is 0.01,

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then the frequency of a homozygous recessive genotype associated

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with a genetic disease will be 0.0001.

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That's no

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Sequoia DNA crossover when you are led an object.

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However, if mating takes place between individuals

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with an inbreeding coefficient of 0.0 65.

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Their parents were siblings, so they are first cousins.

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Then the frequency increase is more than sevenfold to 0.0007 to

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even usher them to change up the internet.

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Inbreeding depression is estimated
for various populations of farm animals

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because it affects productivity traits usually unfavorably.

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Inbreeding depression is mainly expressed in the form

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of a regression coefficient defining by how much on average

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the value of the trait will change when the inbreeding coefficient

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changes by 1% or 10%.

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The sporting inbred mean if you are,
the change can also be expressed

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as a percentage of the average value
for the trait in the analyzed population.

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The value of the inbreeding coefficient at which the value

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of the trait changes drastically is determined as well.

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By the time you share with me in your

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c of the press, the imprint of a head

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psoriasis is caused by multiple mutations
with small effects due to chance genetic drift.

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Many such mutations may have high frequencies.

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Even a structural batting model patsy was occupied for inbreeding.

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Depression is caused by single rare mutation.

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Thank you for your attention.