Mendelian and Nonmendelian Genetics - PowerPoint Presentation

Slide1

Mendelian and Nonmendelian GeneticsSlide2

GENETIC VOCABULARY

Gene- A specific characteristic of an organisms. (A segment of DNA)Genetics- Branch of biology that focuses on heredity.

Allele- Different versions of a gene. Ex. B or bDominant- The expressed form of a trait, which will completely cover the recessive trait. Ex BRecessive- The “hidden” form of a trait. This trait will only be expressed if there are two copies in an organism. Ex b

Heredity- The passing of traits from parents to offspring.Slide3

GENETIC VOCABULARY

Genotype- The alleles an organisms

carries in it’s genome, Set of alleles.Phenotype- The characteristics you can see in an organism. Physical appearance, personality, talents, weaknesses, etc.

Homozygous- Two alleles that are the same. Ex.BB or bbHeterozygous- Two alleles that are different, Ex. Bb Slide4

GENETIC VOCABULARY

Monohybrid – A genetic test cross where only one trait is analyzed.Dihybrid – A genetic test cross where two traits are analyzed.

Punnett Square – The square graphic used when completing genetic problems. Slide5

COMPLETE DOMINANCE

The allele of a gene completely covers the expression of another allele of the same gene.

The gene in this example is color. This color gene has two alleles, red and white.

X

=

Parents

OffspringSlide6

COMPLETE DOMINANCE

To solve using a Punnett square you first assign a letter to represent the alleles of the target gene. In this example we are targeting the color gene.

The dominant color is red so the letter “R” is used.

Capital “R” represents red.Lower case “r” represents white.NEVER ASSUME THE LIGHTER COLOR IS RECESSIVE, THERE ARE PLENTY OF GENETIC CASES WHERE THAT IS NOT THE CASE, READ YOUR PROBLEMS CAREFULLY.

Since you are only working with one gene, a monohybrid Punnett square is sufficient.

Each parent has two alleles, one from their mother and the other from their father. Slide7

COMPLETE DOMINANCE

In this problem we can safely assume the parents are both homozygous for their alleles because all of the children are red.

Place the alleles for the father on top of the Punnett

square in the sperm cells. Place the alleles for the mother on the side of Punnett square in the eggs. Each box represents a genetic POSSIBILTY for the a child.

From the red rose and white rose in a complete dominant scenario all the children produced will be red.Four heterozygous red roses.

Each offspring of the F1 generation has two alleles, one from their mother and the other from their father. Slide8

COMPLETE DOMINANCE

In complete dominance offspring cross the recessive allele will reappear in the F2 generation.

Place the alleles for the father on top of the

Punnett square in the sperm cells. Place the alleles for the mother on the side of Punnett square in the eggs. Each box represents a genetic POSSIBILTY for the a child.

From the two F1 red parents, there is a 75% chance of creating a red rose and a 25% chance of creating a white rose.

One homozygous red, two heterozygous red and one homozygous white.

Each offspring has two alleles, one from their mother and the other from their father. Slide9

COMPLETE DOMINANCE

Here is a graphic of traits which exhibit complete dominance in humans.Slide10

INCOMPLETE DOMINANCE

A phenotype intermediate between the two parents. Appearance of a third phenotype

. A blending between the two alleles.

Parents

X

=Slide11

INCOMPLETE DOMINANCE

To solve using a Punnett square you first assign a letter to represent the alleles of the target gene. In this example we are targeting the color gene.

The dominant color is red so the letter “R” is used.

Capitol “R” represents red.Lower case “r” represents white.NEVER ASSUME THE LIGHTER COLOR IS RECESSIVE, THERE ARE PLENTY OF GENETIC CASES WHERE THAT IS NOT THE CASE, READ YOUR PROBLEMS CAREFULLY.

Since you are only working with one gene, a monohybrid Punnett square is sufficient.

Each parent has two alleles, one from their mother and the other from their father. Slide12

INCOMPLETE DOMINANCE

In this problem we can safely assume the parents are both homozygous for their alleles because all of the children are

pink.

Place the alleles for the father on top of the Punnett square in the sperm cells. Place the alleles for the mother on the side of Punnett square in the eggs.

Each box represents a genetic POSSIBILTY for the a child. From the red rose and white rose in a complete dominant scenario all the children produced will be

pink.

Four heterozygous pink roses.

Each offspring of the F1 generation has two alleles, one from their mother and the other from their father. Slide13

INCOMPLETE DOMINANCE

Incomplete dominance F1 offspring cross the recessive allele will reappear in the F2 generation and all three phenotypes can be seen.

Place the alleles for the father on top of the

Punnett square in the sperm cells. Place the alleles for the mother on the side of Punnett square in the eggs. Each box represents a genetic POSSIBILTY for the a child.

From the two F1 pink parents, there is a 25% chance of creating a red rose, 50% chance of creating a pink rose and a 25% chance of creating a white rose.

One homozygous red, two heterozygous pink and one homozygous white.

Each offspring has two alleles, one from their mother and the other from their father. Slide14

INCOMPLETE DOMINANCE HUMAN TRAITS

Many human genes are incomplete dominance, a blending of two alleles.

Skin color, eye color, hair texture are all incomplete dominance and blend.They are also controlled by many alleles not just two. This is why we have such a wide range of skin, eye and hair textures. Slide15

INCOMPLETE DOMINANCE:HUMAN EYE COLOR

When studying human eye color scientists have found 15 different genes (so far), each with their own set of alleles.

The range of eye colors found in humans can hardly be properly documented with so many different variations dependent on multiple alleles. Slide16

INCOMPLETE DOMINANCE:HUMAN HAIR TEXTURE

From the curliest spirals to the straightest tresses, hair texture has a variety of genes which accounts for the many types of curls and waves.

A straight haired parent and a curly haired parent can create a child with nearly any hair texture imaginable based because you never know what other genes are in their ancestry.Slide17

INCOMPLETE DOMINANCE:HUMAN SKIN COLOR

Human skin color has at least ten identified genes which have different alleles and mutations.

Coupled with the environment and amount of sun a person is exposed to, the variations of skin color are infinite. Slide18

CODOMINANCE

Erminette Chickens

Two dominant alleles are expressed at the same time creating a third phenotype.

Erminette chickens are a cross between a white chicken and black roster, or vice versa creating offspring that have white and black feathers.

When you look at each feather individually it is either all black or all white. Slide19

CODOMINANCE

Roan Cow

Roan cattle occur in the same manner. It is the cross between a red cow and white bull, or vice versa.

The resulting offspring have both white hair and red hair. Giving an odd milky reddish appearance.

When you look at each hair individually it is either all red or all white.

ParentsSlide20

CODOMINANCE

When setting up codominant genetic crosses, it is easiest to assign each trait their respective capitol letter. It helps to remind you that you are working with codominance. Slide21

BLOOD TYPING: Multiple Alleles

The most general method of typing blood is the ABO method.

It was discovered by Austrian-American biologist Karl Landsteiner in 1900, who was awarded the Nobel Prize in 1930.The ABO method focuses on the presence or absence of antigens against type A and B blood.

A type people have antigens against B blood.B type people have antigens against A blood.O type people have no antigens.There are hundreds of other ways to type blood including the Rh – however we will only focus on ABO for now. Slide22

BLOOD TYPING: Multiple Alleles

ABO blood typing has two dominant alleles and one recessive allele.

ABO blood typing has four phenotypes.Slide23

BLOOD TYPING: Multiple Alleles

What are the genotypic possibilities when a heterozygous Type A man has children with a heterozygous Type B woman?Slide24

Autosomes:

1-22

General characteristics for creating a human body.

Sex Chromosomes:

23 only Influence all the genes to be feminine or masculine.

CHROMOSOMESSlide25

SEX CHROMOSOMES

There are two sex chromosomes: X and Y

Normally people have two sex chromosomes.XX is female, but so is a single X.XY is male but so is XXY.Slide26

Sex-linked Traits

Traits controlled by genes on the sex chromosomes (#23). Alleles are written as superscripts on the X and Y chromosomes.

The Y chromosome is only used for male reproductive development and there are a few other genes. The X chromosome is used for female development and for some life sustaining traits

such as blood clotting. Slide27

Sex-linked Trait: Hemophilia

Hemophilia is a recessive blood clotting disorder. The gene is carried on the X chromosome.

Women normally get two X chromosomes thereby having a chance at a normal functioning gene.

However if a male inherits the faulty gene from his X chromosome (mother) he will have hemophilia because his second sex chromosome is a Y and does not carry the gene.

Most people with hemophilia are male, although occasionally women can inherit the gene from both parents. Slide28

PEDIGREES

Pedigrees are diagrams scientists and geneticists use to track inherited disorders through familial generations.

In most pedigrees circles represent females while squares represent males. ALWAYS CHECK THE KEY.

The next slide is the pedigree of hemophilia through Queen Victoria of England. Queen Victoria was a hemophilia carrier.Slide29

Queen Victoria and Royal Hemophilia (Sex-linked trait)Slide30

Sex-linked Trait: Color Blind Gene

The color blind

is a recessive gene is carried on the X chromosome.Women normally get two X chromosomes thereby having a chance at a normal

color viewing gene. However if a male inherits the faulty color gene from his X chromosome (mother) he will have color blindness because his second sex chromosome is a Y and does not carry the gene.

Most people

who can not see color are

male, although occasionally women can inherit the gene from both parents. Slide31

Sex-Linked Trait

Is it red or green??Slide32
Slide33

Sex-linked Trait: Y-Linked

There are a few genetic disorders that are linked to the Y chromosome.

Because the Y chromosome can only be found in males, these disorders ONLY affect males. AzoospermiaAbnormal / absent testicular development.

Retinitis Pigmentosa Slide34
Slide35

DIHYBRID GENETIC CROSS

In a dihybrid genetic cross two genes are analyzed. The Punnett square for dihybrid crosses have 16 boxes / possibilities.

You must also figure out all the possible genetic combinations of the parent’s alleles.Slide36

DIHYBRID GENETIC CROSS: Peas

You will have two pairs of alleles for each parent. The easiest way to determine the genotypes of the gametes is to create a monohybrid cross for the gametes.

We will be looking at the inheritance pattern of pea plants. The two genes will be color and texture. We will use G for color; G = green, g = yellowWe will use T for texture: T = smooth, t = wrinkled

A homozygous green smooth pea will be crossed with a homozygous yellow wrinkled pea.

FATHER: GGTT

MOTHER:

ggtt

This is an easy way to determine which alleles to place in the sperm and eggs on the Punnett square.Slide37

Now write the allele combinations into the sperm and eggs and figure out what the genotypes of the children will be.

As you can see all the children come out green and smooth. The dominant traits have covered the recessive. But what happens if you cross two F1?

DIHYBRID GENETIC CROSS: Peas

FISlide38

DIHYBRID GENETIC CROSS: Peas

Now we will see what happens with the F2 generation.

We will use G for color; G = green, g = yellowWe will use T for texture: T = smooth, t = wrinkledA heterozygous green smooth pea will be crossed with a heterozygous green smooth pea

.

FATHER:

GgTt

MOTHERGgTt

This is an easy way to determine which alleles to place in the sperm and eggs on the Punnett square.Slide39

Now write the allele combinations into the sperm and eggs and figure out what the genotypes of the children will be.

The next slide will show you what you should have for the offspring.

DIHYBRID GENETIC CROSS: Peas

F2Slide40

The F2 generation results in four different phenotypes.

You will have 9 green smooth peas, 3 green wrinkled peas, 3 yellow smooth peas and 1 yellow and wrinkled pea.

DIHYBRID GENETIC CROSS: Peas

F2Slide41

DIHYBRID GENETIC CROSS: Epistasis

Epistasis is a genetic phenomenon where the presence of one gene affects the other.

We will be looking at the inheritance pattern color in mice.We will use B for specific color; B = black, b = brownWe will use C for color expression: C = color, c = no color.

No matter what the specific color is, if there are “cc” the fur will be white. A homozygous black mouse (BBCC) will be crossed with a homozygous white mouse (bbcc).

FATHER: BBCC

MOTHER

bbcc

This is an easy way to determine which alleles to place in the sperm and eggs on the Punnett square.Slide42

Now write the allele combinations into the sperm and eggs and figure out what the genotypes of the children will be.

As you can see all the children come out black with there color appearing. The dominant traits have covered the recessive. But what happens if you cross two F1?

DIHYBRID GENETIC CROSS: Epistasis

FISlide43

DIHYBRID GENETIC CROSS: Epistasis

Now we look and see what happens when two heterozygous black mice are crossed.

We will use B for specific color; B = black, b = brownWe will use C for color expression: C = color, c = no color.No matter what the specific color is, if there are “cc” the fur will be white.

A heterozygous black mouse (BbCc) will be crossed with a heterozygous black mouse (BbCc).

FATHER:

BbCc

MOTHER

BbCc

This is an easy way to determine which alleles to place in the sperm and eggs on the Punnett square.Slide44

Now write the allele combinations into the sperm and eggs and figure out what the genotypes of the children will be.

Continue to the next slide to see the variety of genotypes and phenotypes.

DIHYBRID GENETIC CROSS: Peas

F2Slide45

Remember mice with “cc” are all white, no color expression.

You have 9 black mice, 3 brown mice and 4 white mice.

DIHYBRID GENETIC CROSS: Peas

F2