~~~Sunshínє's Genetics Training~~~

I am glad that you are enthusiastic about learning genetics! :) At times you may have trouble understanding what I am talking about and that is normal. But PLEASE tell me when you are having trouble because it will only get more confusing if you keep going without asking questions.

With that in mind though, this is going to be fun. :)

Okay, so here is my guide about genetics. If you are ever stuck you can refer to this to see if that helps.

https://docs.google.com/file/d…WxReEIyLU56V0E/edit?pli=1

So first things first. Skin color is controlled by pigments called Melanin. Everything has it. Melanin protects your skin from the sun.
"Melanin: The pigment that gives human skin, hair, and eyes their color. Dark-skinned people have more melanin in their skin than light-skinned people have. Melanin is produced by cells called melanocytes."

There are two different types of melanin cells in cats. Eumelanin and Pheomelanin. Eumelanin is the normal type and Pheomelanin is the mutated type.

Eumelanin is what makes a cat look black, chocolate, or cinnamon. When the cat has the mutated version called Pheomelanin, the cat loses the ability to produce melanin and the cat ends up looking red/orange.

So we are first going to focus on Eumelanin colors because those are the easiest to start with.

Genotypes:

Eumelanin-based pigments: (B, b, bl)
Black is produced when the cat has at least one "B" gene.
Chocolate is produced when the cat lacks the "B" gene and has at least one "b" gene.
Cinnamon is produced when the cat lacks both the "B" and the "b" gene and has two "bl" genes.
These pigments are just black with reduced intensity.

A black cat would be "BB, Bb, or Bbl" (If the cat is not carrying anything it would be "BB")
A chocolate cat would be "bb, or bbl" (If the cat is not carrying anything it would be "bb") - (chocolate can never have a "B" because chocolate is recessive to black)
A cinnamon cat can ONLY be "blbl" (this is because cinnamon is recessive to both chocolate and black)

I want you to guess the genetic code for the following cats:

Black Cat:
Chocolate Cat:
Cinnamon Cat:

Sunshínє wrote:

Black would be B
Chocolate would be b
And Cinnamon would be :)

Correct?

Yes. You are correct except something went wrong for cinnamon. You accidentally typed a smiley face. :P

I realized that I failed to talk about dominant and recessive traits.

Okay, so let me back track a bit.

Have you learned about chromosomes and about Mendel's Pea experiments in school yet? :)

Okay, we will go over some basics. I will put key words in bold and I will provide a short key words list at the bottom of each lesson.

A Gene is a trait that is passed from parent to offspring. Number of toes and hair color are examples of different types of different genes.

In this case we will be talking about cats and for each gene, a cat will get two alleles (one from the mother and one from the father).

In this case, we have 3 different alleles that code for normal coat color. This gene is often referred to as the cat's Base Color. So if you see anyone talking about the Base Color of a cat, they are referring to the Eumelanin colors.

In cats, the Black Phenotype is the most dominant and will show up as the cat's color as long as they have at least one "B" allele. The Chocolate Phenotype is the second most dominant and will only show up if the cat doesn't have a "B" allele but DOES have at least one "b" allele. The Cinnamon Phenotype is recessive to both Black and Chocolate and will ONLY show up if the cat receives a "bl" from both parents.

Black = BB, Bb, or Bbl
Chocolate = bb or bbl
Cinnamon = blbl

So from looking at which alleles code for black, chocolate, and cinnamon, you should be able to see which allele is the most dominant and which allele is the most recessive.

Now when a cat has two of the same allele (ex: BB) the cat is said to be homozygous for that trait. And when a cat has two different alleles (ex: Bb) the cat is said to be heterozygous for that trait.

Each set of traits has two different ways of describing it. The phenotype and the genotype.

Phenotype refers to the the physical description of that allele.
Genotype refers to the genetic description of that allele.

For Base Color, the phenotype refers to the colors (black, chocolate, and cinnammon), and the genotype refers to the allele combination (ex: BB, bb, blbl).

To figure out what color the kittens will be when you cross two Eumelanin colored cats, you set up a punnet square using the genotypes of the parents. :)
Click Here for a Punnet Square reference PDF

For now we are going to assume that these cats are homozygous for Base Color. Since the base color isn't gender specific, it doesn't matter which is the male and which is the female, but I will let you know which is which.

So if we were going to do a cross of a male Black cat and a female Black cat, the punnet square would look like this:

B B

B BB BB

B BB BB

What does this mean? This means that when crossing two black cats that are both Homozygous for that trait, the phenotype of all of their offspring will be Black.

So if I were to write this out it would look like this:

Black x Black

Black

So when you do pairings, you will write out your answers like this: (replacing the male, female, and offspring with colors of course) When you are doing pairings for other people you don't have to write out the punnet square, but for practice I want you to write it out.

Male x Female

Offspring

Review Questions:

1) What does it mean for a trait to be dominant? recessive?

2) For base color, write out the colors (not alleles) in order of most dominant to recessive.

3) Based on the Genotypes, can you name the Phenotypes of the following cats?

BB =

blbl =

bbl =

4) Figure out the offspring of these cat pairings: (for these problems, assume that the parents are homozygous for their colors)

Black male, Black female:

Chocolate male, Black female:

5) Figure out the offspring for these cat pairings: (for these problems, assume that the dominant colored parent is heterozygous for the color of the recessive colored parent)

Cinnamon male, Chocolate female:

Black male, Cinnamon female:

**Make sure you follow the template that I used in the example above.** (You can copy and paste this template (below) if that helps - just replace the female with the female's color, and the male with the male's color)

Also, if you are like me and you learn well from visual examples you can watch this video. :)

Sunshínє wrote:

I can answer 1-3, but I'm not too sure about 5 and 6. It's just that I'm not sure what the homozygous and heterozygous factors have on the off spring. But, here's what I could answer:

1.) Dominate alleles produce dominate phenotype. If it is passed from at least one parent, it will show. Recessive alleles produce recessive phenotype. If a recessive allele is to show, it must be passed from both parents.

2.) Black, Chocolate, Cinnamon

3.) Black
Cinnamon
Chocolate

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You got the third question incorrect. Re-read the question again to see if you can spot your mistake. :) If not I will show you.

Review the key words list if you are having difficulties with the meanings. And if you write it out in the punnet square you will be okay. :)

Example:

~~For Homozygous pairings (only applies to the dominant color)~~

Black male, cinnamon female:

Step 1: Figure out which one is the dominant color. (In this case, Black is the dominant color)

Step 2: Figure out if the question asks for the dominant color to be homozygous OR heterozygous. (In this case the dominant color will be homozygous - two copies of the same allele).

Step 3: Write out the alleles:

Black (Homozygous) = BB
Cinnamon = blbl

Step 4: Create the punnet square:

Black

B B
bl Bbl Bbl
Cinnamon
bl Bbl Bbl

Step 5: Analyze the punnet square. (This shows that all of the kittens will be black since Black (B) is the dominant phenotype and there are no (blbl) pairings).

Step 6: Write out the paring as "Male x Female"

Black x Cinnamon

Black

Now if we were doing a heterozgous pairing it would look like this:

~~For Heterozygous pairings (only applies to the dominant color)~~

Black male, cinnamon female:

Step 1: Figure out which one is the dominant color. (In this case, Black is the dominant color)

Step 2: Figure out if the question asks for the dominant color to be homozygous OR heterozygous. (In this case the dominant color will be heteryzygous - one copy of the dominant allele and one copy of the recessive allele).

Step 3: Write out the alleles:

Black (Homozygous) = Bbl
Cinnamon = blbl

Step 4: Create the punnet square:

Black

B bl
bl Bbl blbl
Cinnamon
bl Bbl blbl

Step 5: Analyze the punnet square. (This shows that there can be black kittens and cinnamon kittens since both genotypes show up in the punnet square).

Step 6: Write out the paring as "Male x Female"

Black x Cinnamon

Black, Cinnamon

Does this help?

Okay. :) Go ahead and do the two questions you skipped. :)

4) Figure out the offspring of these cat pairings: (for these problems, assume that the parents are homozygous for their colors)

Black male, Black female:

Chocolate male, Black female:

5) Figure out the offspring for these cat pairings: (for these problems, assume that the dominant colored parent is heterozygous for the color of the recessive colored parent)

Cinnamon male, Chocolate female:

Black male, Cinnamon female:

Are you going to attempt the questions? :)

Just wanted to check in. I hope you haven't given up on learning genetics.

LEXI ! wrote:

4.)
Black x Black

Black

Punnet Square

Male
B B

Female B BB BB

B BB BB

Chocolate x Black

Black

Punnet Square

Male
b b

Female B Bb Bb

B Bb Bb

5.)
Cinnamon x Chocolate

Cinnamon, Chocolate

Punnet Square

Male
bl bl

Female b bbl bbl

bl blbl blbl

Black x Cinnamon

Black, Cinnamon

Punnet Square

Male
B bl

Female bl Bbl blbl

bl Bbl blbl

Done!!!

FIANALLY!

I understand now!

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Perfect! All are correct!! I am so happy you got the format of the litters down 100% perfectly!

Awesome!

So you already know how the 3 Eumelanin Base Colors are Black, Chocolate, and Cinnamon. And that the Base Color genes are B, b, and bl.

Next we are going to learn about a set of genes that alter the Base Color called Dilute but first we need to know how the Eumelanin pigments work.

Each pigment (black, chocolate, and cinnamon) is a slightly different shape, and this shape difference is what gives you the different color. Those pigments are compacted into each strand of hair.

The dilute gene alters this by spreading apart those pigments which causes the cat to appear lighter (and therefore diluted).

Ignore the middle (Caramelized versions) for now because we will learn about those later but these graphics are a pretty decent visualization of what I am describing.

So as you can see, the diluted versions are as follows:

Dense --> Dilute
Black --> Blue
Chocolate --> Lilac
Cinnamon --> Fawn

The dilute alleles are represented by "D" and "d". Dense (D) is dominant over Dilute (d).

Now when we write out the genotype of cats we will also be including the dense/dilute alleles as well. So each cat will now be written with 2 pairs of alleles.

Example:

Black = BB DD

I want you to guess the genotypes for the following phenotypes:

Chocolate =

Fawn =

Blue =

Black =

Now guess what the phenotype is based on these genotypes:

Bb dd =

bb dd =

blbl Dd =

bbl dd =

LEXI ! wrote:

YAY!!! I didn't fail this time!
Trust me, I failed many many many times on paper. I killed many papers practicing this XD

Sorry, not sorry

XD
...

Wow...

And I thought the first lesson was hard XD!

So...
Chocolate= b
Fawn= bl dl?
Blue= B D
Black= B

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Now remember, each gene has 2 alleles. So redo them with this in mind. There are 2 genes now.

Example:

Black = BB DD

Because Black itself is BB and Dense is DD. Black is a dense color.