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The name of the speaker is Katarzyna Andraszek, and she works for the Institute of Animal Science and Fisheries
Faculty of Agrobioengineering and Animal Husbandry
in Siedlce this University of Natural Sciences and Humanities.
She would like to present a presentation on Heterosis, inbreeding depression.
Heterosis means hybrid vigour increased viability
and vigour of animals and plants derived by crossbreeding genetically different forms.
Heterosis is the opposite of inbreeding depression,
and is manifested as an increase in fertility, body size, growth rate
and other traits caused by higher heterozygosity in F1
individuals obtained by crossing two different homozygous lines.
The phenomenon of heterosis is widely exploited in plant and animal breeding.
To obtain heterozygous individuals
and the effect of heterosis
it is necessary to mate individuals
from lines that are as homozygous as possible and therefore at high risk of inbreeding depression.
The effect of heterosis is best seen when inbreeding depression
previously occurs but is not so severe
that it greatly reduces the viability
or fertility of animals.
Individuals of the F1 generation
will have values of traits (including productivity)
at a level represented by
the pure parent line with the higher value for the trait.
The effect of heterosis will occur
only in the first generation obtained
by crossing the parent lines.
The successive F2, F3, .... Fn generations
will have normal parameters
of traits and will not exhibit the hybrid vigour effect.
The genetic background of heterosis
is explained by two hypotheses.
The overdominance hypothesis assumes
that the combination
of two opposing alleles at a given locus in the heterozygote has a greater,
more beneficial effect than the two identical alleles
in the homozygote; for example, heterozygous individuals (Aa)
are resistant to more parasites than homozygous individuals (AA or aa),
In heterozygous individuals,
both allelic forms (dominant and recessive)
of the gene are expressed,
so that the effects of their expression overlap,
ultimately resulting in a higher value for the trait.
On the graph here we can see the effect of enhanced gene expression
in individuals of the F1 generation.
The size
of the oval illustrates the value
of the trait in individuals of a given group
The dominance
hypothesis assumes
that the deleterious effect of recessive alleles
is manifested to a lesser extent in heterozygous individuals
than in recessive homozygotes
On the graph
here we can see
the deleterious effect
of the recessive allele.
The size of the oval
illustrates
the value
of the trait
in individuals of a
given group.
The two hypotheses
have different consequences
in gene expression.
The main cause
of heterozygous is overdominance
then certain genes should be overexpressed in the offspring relative to the parents
due to the overlapping of the effects of the two alleles.
In contrast,
if it is the other hypothesis that explains the better condition of crossbred,
then fewer genes with low expression should be manifested
in the offspring in comparison with the parents.
In addition
virtually the expression
should be comparable
to that observed
in the superior parent.
The heterosis effect is often exploited in plant breeding.
Special parent lines are often bred in order
to obtain hybrids that will be more productive.
An example of exploitation of heterosis,
which is very widespread in plant breeding is maize grain for grain.
The now you have enough.
Now I would like to present some examples of the effects
of heterosis in animal breeding
AIn cattle, Aberdeen Angus x Hereford crossbreds,
known as „Black Baldy”, which are very popular in North America,
Australia and New Zealand have higher values for meat traits.
In addition,
this cross is used
in heifers in order to obtain calves of smaller size
and thus reduce the risk of complications during delivery,
which are characteristic of Herefords „Black Baldy” cows
also have very good maternal characteristics.
In pigs,
an example is Hampshire x Yorkshire crossbreds
known as „Blue Butts”
In poultry,
the two breeds White Rocks
x White Cornish
are crossed to obtain commercial
broilers.
The crossbreds inherit greater body size from the White Cornish breed,
and greater daily weight gains from White Rocks.
Estimation of the effects of heterosis
The effect of heterosis and its magnitude can be defined as:
the percentage increase in the value of a trait relative to the parent population with the better value for the trait,
the percentage increase in the value of
heterozygotes relative to the average for one parent population or the average value for both parent populations,
the percentage increase in the value
of zero.
The percentage
increase in the value
of a trait in the F1 generation relative to the best value observed
in commercial cultivation in a given region used for plants.
The effect
of heterosis can be estimated by comparing the values
of the parent populations and the populations resulting from cross-breeding.
If the value of the traits in parent line a
a is the following equation where: µ – average value of the trait in the population;
aA – effect of direct genetic factors (breeding value)
mA – maternal genetic effect and the value of the trait in parent population B (µB)
is expressed by the following equation
where: µ - average value of the trait in the population;
aB – effect of direct genetic factors (breeding value);
mB – paternal genetic effect.
If hidden
beneath, then the value of the traits in the F1 generation obtained by mating line
A Females with line B males will be expressed by the equation below.
Laws should
imagine Lego
effort mapped in this plot as a pet,
whereas the value obtained by mating of males from line B
with females from linear will be expressed by the following equation.
Your virtuous circle populous of hidden
little red Nevada outer circle popularity plus
popularity olsavsky e map tonight
where HB is the effect of heterozygous
B expressed in the units used for a given trait f
lg Montana ultra itself, but also
based on these assumptions,
the effect of hetero CIS can be estimated according to the following formula.
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some time using the app minnows should
hold of Lana,
but Pulaski approaches
to Sammy when usage of Vanya is in.
Sometimes however,
crossing of inbred parent lines does not result in head to races,
and the crossbreed offspring has the same trait values
as the parents or inferior values.
The of
this phenomenon is called out breeding depression.
It affects wild animal populations more often
than farmed animals and is most likely linked to the fact that the parent populations
are better adapted as a result of long term selection for specific environmental conditions.
Manifesting the best values of the traits
to traits.
Heterozygous offspring, on the other hand,
leads these abilities through mixing of the effects of the animals.
This may also be linked to insufficient genetic distance between the parent populations,
so that heterozygous does not appear in the offspring of a group.
The initial kit that elzey or paternal
colonial needs will ease the pressure in inbreeding.
Depression is one of the main factors reducing the adaptive capacity of inbred organisms
and their viability in comparison to non inbred individuals, significantly increasing the risk of
or ultimately causing the extinction of a population,
especially a small one.
Policy Struggles
Inbreeding depression
may appear in a population in which inbreeding takes place as a consequence
of the increased homosexuality resulting from this type of mating go up.
It's nasty when you can say cohesion proclivities,
rules that underlie my different
ALS have effects of varying strength on the body, on traits
determining adaptation to environmental conditions
which are crucial for the functioning of the body and its survival.
On this ecosystem,
deleterious aliens are eliminated
from the population by natural selection policy problem.
Depressing the problem of inbreeding.
Depression really affects large populations because the effects of deleterious genes are seldom manifested.
Especially when mating is random.
However, it plays an important role
in small populations in which there is a high probability
of inbreeding and of two copies of the same deleterious illegal
being passed on to the offspring in which its effect is manifested.
Voyager one If the frequency of recessive
homozygous in a population in which random mating takes place is kitty,
then in an inbred population, the frequency will be two
plus tcf, whereas is the inbreeding coefficient.
This has a significant impact on the incidence of diseases
or deleterious traits in the population.
I was not disputing sporting inbred.
Matt doesn't have chance of birth.
In the case of random mating, if the frequency of a recessive animal is 0.01,
then the frequency of a homozygous recessive genotype associated
with a genetic disease will be 0.0001.
That's no
Sequoia DNA crossover when you are led an object.
However, if mating takes place between individuals
with an inbreeding coefficient of 0.0 65.
Their parents were siblings, so they are first cousins.
Then the frequency increase is more than sevenfold to 0.0007 to
even usher them to change up the internet.
Inbreeding depression is estimated for various populations of farm animals
because it affects productivity traits usually unfavorably.
Inbreeding depression is mainly expressed in the form
of a regression coefficient defining by how much on average
the value of the trait will change when the inbreeding coefficient
changes by 1% or 10%.
The sporting inbred mean if you are, the change can also be expressed
as a percentage of the average value for the trait in the analyzed population.
The value of the inbreeding coefficient at which the value
of the trait changes drastically is determined as well.
By the time you share with me in your
c of the press, the imprint of a head
psoriasis is caused by multiple mutations with small effects due to chance genetic drift.
Many such mutations may have high frequencies.
Even a structural batting model patsy was occupied for inbreeding.
Depression is caused by single rare mutation.
Thank you for your attention.