Different Patterns of Inheritance

Intermediate, Codominant, And

Polygenic

Variations of Inheritance

• Intermediate Inheritance• Codominance (multiple alleles)• Polygenic Inheritance

Intermediate Inheritance

• No “dominant” allele– Heterozygous organism has completely

different phenotype

Andalusian Chickens Black male + White female = Blue

baby chick

How is this different from what we already know?...

Neither black or white is dominant over the other

Intermediate Inheritance

Intermediate Inheritance• Not the “blending

hypothesis” !!– Parent phenotypes

cancan reappear in later generations

– cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blendingblending of the of the parental parental traits.traits.

Intermediate Crossing Tips!

• The trick is to recognizerecognize when you are dealing with a question involving incomplete dominance. There are two steps to this:

• 1) Notice that the offspring is showing a 3rd phenotype

• 2) Notice that the trait in the offspring is a blend (mixing) of the parental traits.

Notice!!Different Letters

but still a MONOHYBRID cross!

Codominance• Multiple Alleles = codominance

– The heterozygous expresses BOTH traits together

– Different from intermediate (blends)

Cattle can be red (RR = all red hairs), white (WW = all white

hairs), or rrooaann (RW = red & white hairs together) Whatever…Genetics

rules

Aww.. he has your

eyes

Blood Types

O+ Most frequent

AB- Least

Blood Types

• The A antigen, you have type A blood. – The liquid portion of your blood (plasma) has antibodies that fight

against type B blood. In the United States, about 40% of the white population, 27% of African Americans, 28% of Asians, and 16% of Native Americans are type A.

• The B antigen, you have type B blood. – Your plasma has antibodies that fight against type A blood. In the

U.S., about 11% of the white population, 20% of African Americans, 27% of Asians, and 4% of Native Americans are type B.

• Neither the A nor B antigen, you have type O blood. – Your plasma has antibodies that fight against both type A and type

B blood. In the U.S., about 45% of the white population, 49% of African Americans, 40% of Asians, and 79% of Native Americans are type O.

• Both the A and B antigens, you have type AB blood. – Your plasma does not have antibodies against type A or type B

blood. In the U.S., about 4% of the white population, 4% of African Americans, 5% of Asians, and less than 1% of Native Americans are type AB.

Blood Types

• Type O-negative blood does not have any antigens. – It is called the

"universal donor" type because it is compatible with any blood type.

• Type AB-positive blood is called the "universal recipient" type because a person who has it can receive blood of any type. .

A person who has:

Can receive:

A- blood A-, O- blood

A+ blood A-, A+, O-, O+ blood

B- blood B-, O- blood

B+ blood B-, B+, O-, O+ blood

AB- blood AB-, O- blood

AB+ bloodAB-, AB+, A-, A+, B-, B+, O-, O+

blood

O- blood O- blood

O+ blood O-, O+ blood

Blood Typing!

Danny is type AB

Bianna is type A

What are their genotypes?

What are their possible offspring’s

blood types?

Blood Typing!

Kristina is type B but her mother

was type O

Kyle is type A but his father was type O

What are Kristina and Kyle’s genotypes?

Is it possible for their child to be type O?

Difference b/w Intermediate and

Codominance• With intermediate, get a blending of

the dominant & recessive traits so that the third phenotype is something in the middle (red + white = pink).

• In Codominance, the "recessive" & "dominant" traits appear together in the phenotype of hybrid organisms.

Or the easy way…

• Intermediate– (red + white = pink).

• Codominant– Red + White = Red and white

spotted

Practice, Practice, PRACTICE!

A red-flowered sweet pea plant is crossed with a white-flowered sweet pea plant. All of the offspring are pink. What is the inheritance pattern being expressed?

If roan cows and roan bulls are mated, according to the principle of codominance, ______% of the offspring are expected to be roan.

PolygenicsPolygenics• Multiple GENES affect the traits being expressed

– Skin color

– Hair color

– Eye color

How it works…

Eye Color = Brown

Skin Color = Light

Eye Color = Hazel

Skin Color = Tan

Eye Color

QUICK FIREQUICK FIRE• 1. Explain the difference (and use an example) between intermediate and codominance.• 2. What is polygenics?• 3.Blood type is an example of what type of variation in inheritance• 4. How many phenotypes are visible in intermediate inheritance?

Codominance?

ExperimentExperiment

Sex Linked TraitsSex Linked Traits• Sex Chromosomes (X, Y)Sex Chromosomes (X, Y)

– In humans male determined sex of offspringIn humans male determined sex of offspring• Give X = femaleGive X = female• Give y= maleGive y= male

• Genes can be located on sex chromosomes = Sex Linked Traits– Mostly on X for humans

Discovered by Thomas Morgan when experimenting with fruit fly eye color

Fruit Fly Eyes…Oh Fruit Fly Eyes…Oh mymy

• Normally fruit flies have red eyes– Notice some had white– But none of them female!!But none of them female!!– Figured out that the trait for eye color

(red) is located only on the X chromosome• Explains why males are white eyed

Red is dominant to White

Fly ExperimentFly Experiment

• Eye color carried on X• R = red r = white

• More males are white than female be cause

Male XY Female XX

Sex Linked Sex Linked DiseaseDisease

Females can be carriers, males will show it

• Red- green color blindness

• Night Blindness

• Fragile X syndrome

• Sickle Cell Anemia

• Huntington's disease

• Hemophilia MOST sex linked recessive

Sex-Linked Genetic Cross

No Traits

carried on “Y”

This is why MALES

usually show the

recessive trait!!

Triple P Time!!Triple P Time!!PPractice ractice PProblem roblem PPacket!!acket!!

You are now ready to complete the BOLDBOLD questions…