Post by ☆ hollow on May 19, 2014 6:28:22 GMT
Introduction
Genetics...jeez. What to say about genetics and all it's confusing rules and what not? Well, it can be simplified.
Sometimes, even the most complex thing can be broken down into smaller bits. We all just need to take a deep breath and work out the simple steps. We can all do simple right? I mean, unless you burn water. In that case, you might want to turn around. Just kidding! This is for anyone and everyone.
Of course, genetics won't be as simple as I am making it sound considering there is so much to this. I'm just making it easier to understand. I won't go into too much detail about this and that, but I will do a few simple things.
Basis of Genetics
You see a long time ago, there was this monk. He wondered how each plant and animal got their looks. Originally, he came up with the idea of blending, which was later rejected due to the formation of the genetics in the first set of kin. Now, Mendel was studying a purple and white flower that had recessive and dominant traits. Dominant traits, usually the darker colorings, overpower the Recessive traits. Mendel, breeding flowers, had a homozygous dominant breed with a homozygous recessive. Now, I'll teach you this vocabulary later. While he did this, he found that the plants were all purple. But, how? He used a punnet square created by Reginald Punnet (Thank you to Spain for the information). Anyone that has taken Biology should know this square fairly well. This square will be your best friend when it comes to one single trait.
Now, he found that all the plants were heterozygous. These plants had the recessive gene as well as the dominant gene! So, thus, the study of genetics was founded.
Different Terms
Now, there are a lot of different terms. I am going to break these down for you so that you better understand. Some terms can be a little murky.
● Heredity is the transmission of traits from one generation to the next.
● Genetics is the scientific study of heredity.
● A cross between two individuals differing in a single character is a monohybrid cross.
- this is usually homozygous dominant and homozygous recessive
● Alleles are alternative versions of genes that account for variations in inherited characters
● A homozygous genotype has identical alleles.
● A heterozygous genotype has two different alleles.
● If the alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele.
The other has no noticeable effect on the organism’s appearance and is called the recessive allele.
● The phenotype is the appearance or expression of a trait.
- phenotype: a black cat with golden eyes
● The genotype is the genetic makeup of a trait.
-genotype: BBGGDD {B=Black G= Gold D= Dense}
● A dihybrid cross is a mating of parental varieties that differ in two characters.
-heterozygous breeding.
● Mendel’s pea crosses always looked like one of the parental varieties, called complete dominance.
● For some characters, the appearance of F1 hybrids falls between the phenotypes of the two parental varieties. This is called incomplete dominance.
- Incomplete dominance shows both recessive and dominant genes; blending.
● Many characteristics result from polygenic inheritance, in which a single phenotypic character results from the additive effects of two or more genes
● X-Linked Gene: Located close together on the same chromosome and tend to be inherited together.
Work It Out
So, this is where it gets a little more complicated. I mean, it depends on the coloring of the cat. What I suggest is taking notes on the different colorings and such. I usually try to keep mine the same. Sometimes I will use letters that are similar to others, but I know what it means. So, you can essentially use any letter in the alphabet, except for x, for genetics. When you use the letter "x" you have another letter that follows. Now, we are going to do a simple punnet square to begin with.
Phenotypes: Purple Flower x White Flower
Genotypes: PP x pp
Now, the punnet square set up is as follows.
The upper part is the mother's traits, which in this case is "pp", and the left side is the father's traits, which in this case is "PP". Now, we are going to cross these. I won't have a punnet square to show you here, but you can look it up.
Now, with the mother's "p" over one column and then the other over the other column and the father's "P" standing with one row and then "P" standing in the other row. You will get all "Pp". This is our classic heterozygous.
Now, we are going to do a few cat genetics because this is what we are all here for. We need to figure out the genetics of a black cat with a red tabby cat. The tabby gene will be defined later in this, but for now, we will disregard it. So, black crossed with red. During a split of a cell, in Meiosis, the sister choromatids do something called crossing over. The two exchange alleles before becoming a single gamete. A gamete is the rather wonderful single trait, which would be a single letter. This letter signifies dominance or not.
Usually what I do is I create a key first. Since this is genetics broken down, we will be doing this.
The key:
xrxr= red female
xBxB=black
xry= red male
xBy= black male
xBxr= tortie
D= dense
d= dilute
Now, when we do this we have to separate each gamete from each other.
For Black Male:
XBY= black male
For Red Female:
xrxr= red female
For the punnet square, in the beginning, we are not going to worry whether or not something is dilute or dense. For now, we are going to make sure that we just keep our heads above quicksand. Now, the first steps into the punnet square to find out the genetics of your litter. Of course, we begin by creating a four-square punnet square. Later on, we will learn the 16-square punnet square. So, keep to the four.
Top: xb xr
Down: xB
Y
Now, we cross them. When crossing, make sure your gametes are in the right spot. If they are not, then you can seriously screw with the genetics of your litter. This is to get the four different types. Of course, even then, we are not dealing with the dense factors. Now, from the punnet square above, we get three unique genotypes:
xBxr= black tortie female
xBY = black male
xbY = red male.
This is simple for now, but then we get more complex as we break down two or more factors. With all the factors we have in genetics, we can simply state that the beginning punnet square is the start to ever good genetics master. Even I still have a lot to learn about genetics and its factors on the human and animal world. Now, what I showed you was the most difficult of the genotype break downs. This was the X-Linked Genotypes. The non-linked are called autosomal. This is when gender doesn’t play a factor. Remember the break down of the purple and the white flower? That is autosomal. So, essentially, I’ve done both types of punnet squares; X-Linked and Autosomal.
Do you want to keep going? Really? Good! Now, we are going to do two genes together. This is called a Punnet Square as well. Just to make it less difficult, I call this one the Dihybrid Cross. Now, with this usually has two factors, thus the name “di”. Di-, as most of us know, means two. So, this dihybrid cross is going to be one of your best friends in your journey! When we break it down, we are going to be putting several genotypes together. Here we go.
As always, we are going to start with our key from before.
xrxb= red
xBxB=black
xry= red male
xBy= black male
xBxb= tortie
D= dense
d= dilute
Now, we are going to assume that both are heterozygous for dilute. It gives us more variation within our new genotypes and gives us more of a challenge to figure out the phenotypes. This is going to be good! Come on!
Now, we have a dense black male and a dense red female. Both are heterozygous for dilute! Remember heterozygous. This means that they carry both dominant and recessive. The dominant just shows up as the larger lettering of the two and is often the trait that is carried, unless it is certain X-Linked, codominant, incomplete dominance, complete dominance traits.
Now the father is going to be black and the mother a black tortie. The father carries no white spotting or agouti and neither does the mother. The father is homozygous for dense and the mother heterozygous.
We are going to be crossing these. Now, what we do is we pair the genes with each other. We need four down and four across. This is where it can get tricky.
Here it goes.
Top: xBD xrD xBd xrd
Down: xBD xBD YD YD
Now, because of this pairings we will get more genetic variation. This is usually the basics of breaking it down, but I will go into detail with the genotypes of each coat coloring and each variation. This is only for red, black, calico, and torties. Of course, calicoes would have white spotting, which can also lead to deafness, but that is another explanation for later.
Now, the genotypes you get from this cross is:
First Row: xBxBDD xBxrDD xBxBDd xBxrDd
Second Row: xBxBDD xBxrDD xBxBDd xBxrDd
Third Row: xBYDD xrYDD xBYDd xrYDd
Fourth Row: xBYDD xrYDD xBYDd xrYDd
Now, the phenotypes are the simple part of this. It is simple. Just like last time. This is usually the best part. Phenotypes are the physical appearance.
Phenotypes of Black Male x Black Tortie:
females: black female homozygous dense, black female heterozygous dense, black tortie homozygous dense, black tortie heterozygous dense.
male: black homozygous dense, black heterozygous dense, red tabby homozygous dense, red tabby heterozygous dense
Cats Coats and Genotypes:
Black:
xBxBD-
xBYD-
BBD-
BbD-
WIP!
Genetics...jeez. What to say about genetics and all it's confusing rules and what not? Well, it can be simplified.
Sometimes, even the most complex thing can be broken down into smaller bits. We all just need to take a deep breath and work out the simple steps. We can all do simple right? I mean, unless you burn water. In that case, you might want to turn around. Just kidding! This is for anyone and everyone.
Of course, genetics won't be as simple as I am making it sound considering there is so much to this. I'm just making it easier to understand. I won't go into too much detail about this and that, but I will do a few simple things.
Basis of Genetics
You see a long time ago, there was this monk. He wondered how each plant and animal got their looks. Originally, he came up with the idea of blending, which was later rejected due to the formation of the genetics in the first set of kin. Now, Mendel was studying a purple and white flower that had recessive and dominant traits. Dominant traits, usually the darker colorings, overpower the Recessive traits. Mendel, breeding flowers, had a homozygous dominant breed with a homozygous recessive. Now, I'll teach you this vocabulary later. While he did this, he found that the plants were all purple. But, how? He used a punnet square created by Reginald Punnet (Thank you to Spain for the information). Anyone that has taken Biology should know this square fairly well. This square will be your best friend when it comes to one single trait.
Now, he found that all the plants were heterozygous. These plants had the recessive gene as well as the dominant gene! So, thus, the study of genetics was founded.
Different Terms
Now, there are a lot of different terms. I am going to break these down for you so that you better understand. Some terms can be a little murky.
● Heredity is the transmission of traits from one generation to the next.
● Genetics is the scientific study of heredity.
● A cross between two individuals differing in a single character is a monohybrid cross.
- this is usually homozygous dominant and homozygous recessive
● Alleles are alternative versions of genes that account for variations in inherited characters
● A homozygous genotype has identical alleles.
● A heterozygous genotype has two different alleles.
● If the alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele.
The other has no noticeable effect on the organism’s appearance and is called the recessive allele.
● The phenotype is the appearance or expression of a trait.
- phenotype: a black cat with golden eyes
● The genotype is the genetic makeup of a trait.
-genotype: BBGGDD {B=Black G= Gold D= Dense}
● A dihybrid cross is a mating of parental varieties that differ in two characters.
-heterozygous breeding.
● Mendel’s pea crosses always looked like one of the parental varieties, called complete dominance.
● For some characters, the appearance of F1 hybrids falls between the phenotypes of the two parental varieties. This is called incomplete dominance.
- Incomplete dominance shows both recessive and dominant genes; blending.
● Many characteristics result from polygenic inheritance, in which a single phenotypic character results from the additive effects of two or more genes
● X-Linked Gene: Located close together on the same chromosome and tend to be inherited together.
Work It Out
So, this is where it gets a little more complicated. I mean, it depends on the coloring of the cat. What I suggest is taking notes on the different colorings and such. I usually try to keep mine the same. Sometimes I will use letters that are similar to others, but I know what it means. So, you can essentially use any letter in the alphabet, except for x, for genetics. When you use the letter "x" you have another letter that follows. Now, we are going to do a simple punnet square to begin with.
Phenotypes: Purple Flower x White Flower
Genotypes: PP x pp
Now, the punnet square set up is as follows.
The upper part is the mother's traits, which in this case is "pp", and the left side is the father's traits, which in this case is "PP". Now, we are going to cross these. I won't have a punnet square to show you here, but you can look it up.
Now, with the mother's "p" over one column and then the other over the other column and the father's "P" standing with one row and then "P" standing in the other row. You will get all "Pp". This is our classic heterozygous.
Now, we are going to do a few cat genetics because this is what we are all here for. We need to figure out the genetics of a black cat with a red tabby cat. The tabby gene will be defined later in this, but for now, we will disregard it. So, black crossed with red. During a split of a cell, in Meiosis, the sister choromatids do something called crossing over. The two exchange alleles before becoming a single gamete. A gamete is the rather wonderful single trait, which would be a single letter. This letter signifies dominance or not.
Usually what I do is I create a key first. Since this is genetics broken down, we will be doing this.
The key:
xrxr= red female
xBxB=black
xry= red male
xBy= black male
xBxr= tortie
D= dense
d= dilute
Now, when we do this we have to separate each gamete from each other.
For Black Male:
XBY= black male
For Red Female:
xrxr= red female
For the punnet square, in the beginning, we are not going to worry whether or not something is dilute or dense. For now, we are going to make sure that we just keep our heads above quicksand. Now, the first steps into the punnet square to find out the genetics of your litter. Of course, we begin by creating a four-square punnet square. Later on, we will learn the 16-square punnet square. So, keep to the four.
Top: xb xr
Down: xB
Y
Now, we cross them. When crossing, make sure your gametes are in the right spot. If they are not, then you can seriously screw with the genetics of your litter. This is to get the four different types. Of course, even then, we are not dealing with the dense factors. Now, from the punnet square above, we get three unique genotypes:
xBxr= black tortie female
xBY = black male
xbY = red male.
This is simple for now, but then we get more complex as we break down two or more factors. With all the factors we have in genetics, we can simply state that the beginning punnet square is the start to ever good genetics master. Even I still have a lot to learn about genetics and its factors on the human and animal world. Now, what I showed you was the most difficult of the genotype break downs. This was the X-Linked Genotypes. The non-linked are called autosomal. This is when gender doesn’t play a factor. Remember the break down of the purple and the white flower? That is autosomal. So, essentially, I’ve done both types of punnet squares; X-Linked and Autosomal.
Do you want to keep going? Really? Good! Now, we are going to do two genes together. This is called a Punnet Square as well. Just to make it less difficult, I call this one the Dihybrid Cross. Now, with this usually has two factors, thus the name “di”. Di-, as most of us know, means two. So, this dihybrid cross is going to be one of your best friends in your journey! When we break it down, we are going to be putting several genotypes together. Here we go.
As always, we are going to start with our key from before.
xrxb= red
xBxB=black
xry= red male
xBy= black male
xBxb= tortie
D= dense
d= dilute
Now, we are going to assume that both are heterozygous for dilute. It gives us more variation within our new genotypes and gives us more of a challenge to figure out the phenotypes. This is going to be good! Come on!
Now, we have a dense black male and a dense red female. Both are heterozygous for dilute! Remember heterozygous. This means that they carry both dominant and recessive. The dominant just shows up as the larger lettering of the two and is often the trait that is carried, unless it is certain X-Linked, codominant, incomplete dominance, complete dominance traits.
Now the father is going to be black and the mother a black tortie. The father carries no white spotting or agouti and neither does the mother. The father is homozygous for dense and the mother heterozygous.
We are going to be crossing these. Now, what we do is we pair the genes with each other. We need four down and four across. This is where it can get tricky.
Here it goes.
Top: xBD xrD xBd xrd
Down: xBD xBD YD YD
Now, because of this pairings we will get more genetic variation. This is usually the basics of breaking it down, but I will go into detail with the genotypes of each coat coloring and each variation. This is only for red, black, calico, and torties. Of course, calicoes would have white spotting, which can also lead to deafness, but that is another explanation for later.
Now, the genotypes you get from this cross is:
First Row: xBxBDD xBxrDD xBxBDd xBxrDd
Second Row: xBxBDD xBxrDD xBxBDd xBxrDd
Third Row: xBYDD xrYDD xBYDd xrYDd
Fourth Row: xBYDD xrYDD xBYDd xrYDd
Now, the phenotypes are the simple part of this. It is simple. Just like last time. This is usually the best part. Phenotypes are the physical appearance.
Phenotypes of Black Male x Black Tortie:
females: black female homozygous dense, black female heterozygous dense, black tortie homozygous dense, black tortie heterozygous dense.
male: black homozygous dense, black heterozygous dense, red tabby homozygous dense, red tabby heterozygous dense
Cats Coats and Genotypes:
Black:
xBxBD-
xBYD-
BBD-
BbD-
WIP!