0:00:00.000,0:00:07.000
Hello everyone, I welcome you to another lecture from the Animal Breeding module, the topic of which is: 

0:00:07.000,0:00:14.000
Quantitative traits and path way coefficients. In the lecture, we will introduce quantitative traits

0:00:14.000,0:00:17.000
and the descriptions of path way coefficients.

0:00:17.000,0:00:26.000
If we are talking about the performance of an individual, we are talking about the so-called phenotype.

0:00:26.000,0:00:34.000
The phenotype is a set of traits observed on individual and is a function of genotype and environment.

0:00:34.000,0:00:46.000
It is therefore a set of all the traits of an individual that are of interest to us from the point of view of animal genetics.

0:00:46.000,0:00:56.00
If we use the basic definition of the phenotype. The phenotype is always defined as a function of the genotype

0:00:56.000,0:01:02.000
and the environment. We can define the phenotype as the sum of the level of the genotype,

0:01:02.000,0:01:09.000
the environment and the relationship or interaction between the genotype and the environment. 

0:01:09.000,0:01:14.000
If we convert this relationship into phenotypic variance,

0:01:14.000,0:01:24.000
then phenotypic variance is influenced by genetic variance, environmental variance and covariance between genotype and environment.

0:01:24.000,0:01:32.000
Genetic variance can be divided into variability influenced by the additive component of the genotype,

0:01:32.000,0:01:42.000
variance influenced by the dominance component and variance influenced by the component of gene interactions or epistasis.

0:01:42.000,0:01:50.000
Environmental variance can be divided into variance influenced by the permanent or temporary environment.

0:01:50.000,0:01:57.000
This slide will explain the terms additivity, dominance and interaction.

0:01:57.000,0:02:04.000
The concept of additivity can be explained as follows. Each gene has some effect.

0:02:04.000,0:02:12.000 
It is generally assumed that the dominant allele shows a higher performance value

0:02:12.000,0:02:18.000
(e.g. 5 kg on average) than the recessive allele (e.g. 2 kg on average).

0:02:18.000,0:02:25.000
The genetic value of the given individual for which we are considering the given genotype,

0:02:25.000,0:02:30.000
affected only by the additivity effect, is 38 Kg.

0:02:30.000,0:02:37.000
We obtained this value by summing the individual effects of individual genes.

0:02:37.000,0:02:47.000
Conversely, dominance represents the relationship of two genes or two allels at one locus.

0:02:47.000,0:02:53.000
For example: If it exists, let's call it over-dominance.

0:02:53.000,0:03:09.000
That is, if the alleles at one locus are heterozygous, then is an increase in productivity by, for example, 10 kg.

0:03:09.000,0:03:16.000
The genetic value of the given genotype affected only by the dominance effect (D) is,

0:03:16.000,0:03:27.000
therefore, 20 kg since it contains only two gene pairs in the heterozygous state.

0:03:27.000,0:03:35.000
And interaction, or epistasis, represents the relationship between two genes at different loci.

0:03:35.000,0:03:44.000
Suppose there is a relationship between the dominant allele A and the dominant allele B,

0:03:44.000,0:03:55.000
and this relationship increases performance by 10 kg. Therefore, in the genotype we are considering,

0:03:55.000,0:04:02.000
the interaction effect will increase productivity or performance by 20 kg

0:04:02.000,0:04:13.000
because the genotype contains one dominant allele A and two dominant alleles B.

0:04:13.000,0:04:22.000
By summing the effects of additivity, and dominance and the interaction,

0:04:22.000,0:04:31.000
we get the total genetic value, which is 78 kg for the genotype we are considering.

0:04:31.000,0:04:38.000
From the point of view of animal breeding, the transfer of genetic information from

0:04:38.000,0:04:41.000
individuals to subsequent generations is important.

0:04:41.000,0:04:47.000
This transmission takes place using sex cells or gametes.

0:04:47.000,0:04:56.000
As we already know, gametes carry half the number of chromosomes and there are so-called "haploid".

0:04:56.000,0:05:03.000
An individual with the genotype listed here has these four types of gametes.

0:05:03.000,0:05:15.000
For each gamete, there is an additive effect of genes because each gamete contains that individual's genes.

0:05:15.000,0:05:24.000
The effect of dominance and interaction by forming gametes disappears because the gametes are haploid;

0:05:24.000,0:05:30.000
therefore, there can be no interactions at the locus level.

0:05:30.000,0:05:41.000
In some gametes, the interaction effect also does not occur due to random segregation of alleles or chromosomes.

0:05:41.000,0:05:47.000
Only half of the additive genetic effect is transfers through the gametes.

0:05:41.000,0:05:54.000
Thanks to the formation of gametes and the transmission of a genetics

0:05:54.000,0:05:59.000
or rather additive genetic effect between parents and offspring,

0:05:59.000,0:06:05.000
it is possible to observe the genetic similarity between related individuals,

0:06:05.000,0:06:17.000
such as the already mentioned parents and offspring, but also siblings full of half, distant relatives and distant siblings.

0:06:17.000,0:06:26.000
This genetic similarity can be studied thanks to the so-called path way coefficients.

0:06:26.000,0:06:34.000
The pathway coefficients define a relationship or dependence from one variable to other variable,

0:06:34.000,0:06:39.000
i.e., a relationship between at least two variables.

0:06:39.000,0:06:50.000
In general, we distinguish two types of patway coefficients - the first type, where another variable fully determines one variable.

0:06:50.000,0:06:57.000
We professionally call this type the statistical term "regression".

0:06:57.000,0:07:04.000
The second type is regarding the equal status of both variables.

0:07:04.000,0:07:08.000
We professionally call this type of statistical term "correlation."

0:07:08.000,0:07:16.000
Only the following two rules are sufficient for working with pathway coefficients.

0:07:16.000,0:07:25.000
Rule one: If another variable (E) lies between variables X and variable Y,

0:07:25.000,0:07:36.000
the connection from variable X to variable Y consists of two sub-connections (X-E, E-Y).

0:07:36.000,0:07:45.000
The pathway coefficient from variable X to variable Y is obtained as a product of partial connections.

0:07:45.000,0:07:54.000
The second rule: If it is possible to find a more significant number of possible connections between two variables,

0:07:54.000,0:08:04.000
the total connections - the total pathway coefficient, is equal to the sum of the single connections.

0:08:04.000,0:08:12.000
We will present the given rules here in the following case of two full sibs.

0:08:12.000,0:08:19.000
There is no relationship between the phenotype of individual X and individual Y.

0:08:19.000,0:08:25.000
The only possible relationship is through the genetic merit of individuals.

0:08:25.000,0:08:33.000
And that through the genetic equipment of the father and the genetic equipment of the mother.

0:08:33.000,0:08:39.000
Through meiosis, everyone receives half of their parents' genetic merit.

0:08:39.000,0:08:52.000
Here, we will use rule 1 of pathway coefficients: If another variable (E) lies between the variables X and Y,

0:08:52.000,0:09:00.000
the connection from X to Y consists of the product of partial connections.

0:09:00.000,0:09:10.000
In this case, 0.5 x 0.5. The same rule applies to the mother.

0:09:10.000,0:09:20.000
And since these two individuals are full sibs who have the same parents,

0:09:20.000,0:09:31.000
we can use rule 2 of pathway coefficients: If a more possible connections can be found between two variables,

0:09:21.000,0:09:38.000
X and Y, the total pathway coefficient is equal to the sum of the single connections.

0:09:38.000,0:09:43.000
In this case, through the father and the mother.

0:09:43.000,0:09:52.000
The genetic relationship between individuals X and Y equals the value 0.5.

0:09:52.000,0:10:00.000
It is necessary to realize that single connections can be the product of partial connections.

0:10:00.000,0:10:10.000
The same is true for the following case.  We will again use both pathway coefficient rules.

0:10:10.000,0:10:19.000
The genetic relationship between individual X and Y is equal to 0.3125.

0:10:19 .000,0:10:26.000
There are two so-called genetic "paths" between individuals X and Y.

0:10:26.000,0:10:30.000
One is expressed as red and the other as blue.

0:10:30.000,0:10:47.000
The red "path" reaches a value of 0.5 quoters, again assuming that each offspring receives 50% of its genes from its parent,

0:10:47.000,0:11:03.000
and the sub-sections path are multiplied, and the blue "path" reaches a value of 0.5 squered, according to the same rules.

0:11:043000,0:11:10.000
At the end, we add up both paths (blue and red).

0:11:10.000,0:11:23.000
Thus, the genetic value between individual X and Y is equal to the value 0.3125, as already mentioned.

0:11:23.000,0:11:32.000
We proceed similarly when defining the genetic relationship between the offspring

0:11:32.000,0:11:40.000
and own parents when the genetic similarity is equal to the value of one

0:11:40.000,0:11:53.000
and the genetic similarity between the offspring and only one parent when the genetic similarity is similar to the value of 0.5.

0:11:53.000,0:12:03.000
We can continue with half-sibs, when the genetic similarity is equal to 0.25.

0:12:03.000,0:12:11.000
Own siblings, when the genetic similarity is similar to the value 0.5 and,

0:12:11.000,0:12:22.000
for example, a cousin and cousin, when the genetic similarity is equal to the value 0.125.

0:12:22.000,0:12:29.000
From the principles of pathway coefficients mentioned above,

0:12:29.000,0:12:35.000
we can derive rules that are mainly used in the estimation of genetic parameters,

0:12:35.000,0:12:40.000
which include, for example, coefficient of heritability.

0:12:40.000,0:12:47.000
The group of animals related to each other have similar genotypes.

0:12:47.000,0:12:57.000
Therefore, differences within groups of related animals are primarily conditioned by the influence of the environment.

0:12:57.000,0:13:04.000
And further that different groups of related animals have different genotypes.

0:13:04.000,0:13:13.000
Therefore, differences in the performance of related animals in differnet groups

0:13:13.000,0:13:21.000
are mainly caused by differences in the additive genetic part of their gene pool.

0:13:21.000,0:13:28.000
In this lecture, the quantitative traits and the concept of pathway coefficients

0:13:28.000,0:13:35.000
for determining the genetic relationships between two individuals were presented.

0:13:35.000,0:13:41.000
Thank you for your attention and I look forward to seeing you in the next lecture.